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unmap_grant_pages() currently waits for the pages to no longer be used.
In https://github.com/QubesOS/qubes-issues/issues/7481, this lead to a
deadlock against i915: i915 was waiting for gntdev's MMU notifier to
finish, while gntdev was waiting for i915 to free its pages. I also
believe this is responsible for various deadlocks I have experienced in
the past.
Avoid these problems by making unmap_grant_pages async. This requires
making it return void, as any errors will not be available when the
function returns. Fortunately, the only use of the return value is a
WARN_ON(), which can be replaced by a WARN_ON when the error is
detected. Additionally, a failed call will not prevent further calls
from being made, but this is harmless.
Because unmap_grant_pages is now async, the grant handle will be sent to
INVALID_GRANT_HANDLE too late to prevent multiple unmaps of the same
handle. Instead, a separate bool array is allocated for this purpose.
This wastes memory, but stuffing this information in padding bytes is
too fragile. Furthermore, it is necessary to grab a reference to the
map before making the asynchronous call, and release the reference when
the call returns.
It is also necessary to guard against reentrancy in gntdev_map_put(),
and to handle the case where userspace tries to map a mapping whose
contents have not all been freed yet.
Fixes: 745282256c75 ("xen/gntdev: safely unmap grants in case they are still in use")
Cc: stable@vger.kernel.org
Signed-off-by: Demi Marie Obenour <demi@invisiblethingslab.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20220622022726.2538-1-demi@invisiblethingslab.com
Signed-off-by: Juergen Gross <jgross@suse.com>
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1 << 31 is undefined. So switch to 1U << 31.
Fixes: 5ead97c84fa7 ("xen: Core Xen implementation")
Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20220617103037.57828-1-julien@xen.org
Signed-off-by: Juergen Gross <jgross@suse.com>
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EXPORT_SYMBOL and __init is a bad combination because the .init.text
section is freed up after the initialization. Hence, modules cannot
use symbols annotated __init. The access to a freed symbol may end up
with kernel panic.
modpost used to detect it, but it has been broken for a decade.
Recently, I fixed modpost so it started to warn it again, then this
showed up in linux-next builds.
There are two ways to fix it:
- Remove __init
- Remove EXPORT_SYMBOL
I chose the latter for this case because none of the in-tree call-sites
(arch/arm/xen/enlighten.c, arch/x86/xen/grant-table.c) is compiled as
modular.
Fixes: 243848fc018c ("xen/grant-table: Move xlated_setup_gnttab_pages to common place")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>
Link: https://lore.kernel.org/r/20220606045920.4161881-1-masahiroy@kernel.org
Signed-off-by: Juergen Gross <jgross@suse.com>
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Use the presence of "iommus" property pointed to the IOMMU node with
recently introduced "xen,grant-dma" compatible as a clear indicator
of enabling Xen grant mappings scheme for that device and read the ID
of Xen domain where the corresponding backend is running. The domid
(domain ID) is used as an argument to the Xen grant mapping APIs.
To avoid the deferred probe timeout which takes place after reusing
generic IOMMU device tree bindings (because the IOMMU device never
becomes available) enable recently introduced stub IOMMU driver by
selecting XEN_GRANT_DMA_IOMMU.
Also introduce xen_is_grant_dma_device() to check whether xen-grant
DMA ops need to be set for a passed device.
Remove the hardcoded domid 0 in xen_grant_setup_dma_ops().
Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Link: https://lore.kernel.org/r/1654197833-25362-8-git-send-email-olekstysh@gmail.com
Signed-off-by: Juergen Gross <jgross@suse.com>
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In order to reuse generic IOMMU device tree bindings by Xen grant
DMA-mapping layer we need to add this stub driver from a fw_devlink
perspective (grant-dma-ops cannot be converted into the proper
IOMMU driver).
Otherwise, just reusing IOMMU bindings (without having a corresponding
driver) leads to the deferred probe timeout afterwards, because
the IOMMU device never becomes available.
This stub driver does nothing except registering empty iommu_ops,
the upper layer "of_iommu" will treat this as NO_IOMMU condition
and won't return -EPROBE_DEFER.
As this driver is quite different from the most hardware IOMMU
implementations and only needed in Xen guests, place it in drivers/xen
directory. The subsequent commit will make use of it.
Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Link: https://lore.kernel.org/r/1654197833-25362-7-git-send-email-olekstysh@gmail.com
Signed-off-by: Juergen Gross <jgross@suse.com>
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In order to support virtio in Xen guests add a config option XEN_VIRTIO
enabling the user to specify whether in all Xen guests virtio should
be able to access memory via Xen grant mappings only on the host side.
Also set PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS feature from the guest
initialization code on Arm and x86 if CONFIG_XEN_VIRTIO is enabled.
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/1654197833-25362-5-git-send-email-olekstysh@gmail.com
Signed-off-by: Juergen Gross <jgross@suse.com>
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Introduce Xen grant DMA-mapping layer which contains special DMA-mapping
routines for providing grant references as DMA addresses to be used by
frontends (e.g. virtio) in Xen guests.
Add the needed functionality by providing a special set of DMA ops
handling the needed grant operations for the I/O pages.
The subsequent commit will introduce the use case for xen-grant DMA ops
layer to enable using virtio devices in Xen guests in a safe manner.
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Link: https://lore.kernel.org/r/1654197833-25362-4-git-send-email-olekstysh@gmail.com
Signed-off-by: Juergen Gross <jgross@suse.com>
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For support of virtio via grant mappings in rare cases larger mappings
using consecutive grants are needed. Support those by adding a bitmap
of free grants.
As consecutive grants will be needed only in very rare cases (e.g. when
configuring a virtio device with a multi-page ring), optimize for the
normal case of non-consecutive allocations.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/1654197833-25362-3-git-send-email-olekstysh@gmail.com
Signed-off-by: Juergen Gross <jgross@suse.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip
Pull more xen updates from Juergen Gross:
"Two cleanup patches for Xen related code and (more important) an
update of MAINTAINERS for Xen, as Boris Ostrovsky decided to step
down"
* tag 'for-linus-5.19-rc1b-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
xen: replace xen_remap() with memremap()
MAINTAINERS: Update Xen maintainership
xen: switch gnttab_end_foreign_access() to take a struct page pointer
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xen_remap() is used to establish mappings for frames not under direct
control of the kernel: for Xenstore and console ring pages, and for
grant pages of non-PV guests.
Today xen_remap() is defined to use ioremap() on x86 (doing uncached
mappings), and ioremap_cache() on Arm (doing cached mappings).
Uncached mappings for those use cases are bad for performance, so they
should be avoided if possible. As all use cases of xen_remap() don't
require uncached mappings (the mapped area is always physical RAM),
a mapping using the standard WB cache mode is fine.
As sparse is flagging some of the xen_remap() use cases to be not
appropriate for iomem(), as the result is not annotated with the
__iomem modifier, eliminate xen_remap() completely and replace all
use cases with memremap() specifying the MEMREMAP_WB caching mode.
xen_unmap() can be replaced with memunmap().
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>
Link: https://lore.kernel.org/r/20220530082634.6339-1-jgross@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>
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Instead of a virtual kernel address use a pointer of the associated
struct page as second parameter of gnttab_end_foreign_access().
Most users have that pointer available already and are creating the
virtual address from it, risking problems in case the memory is
located in highmem.
gnttab_end_foreign_access() itself won't need to get the struct page
from the address again.
Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
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git://git.infradead.org/users/hch/dma-mapping
Pull dma-mapping updates from Christoph Hellwig:
- don't over-decrypt memory (Robin Murphy)
- takes min align mask into account for the swiotlb max mapping size
(Tianyu Lan)
- use GFP_ATOMIC in dma-debug (Mikulas Patocka)
- fix DMA_ATTR_NO_KERNEL_MAPPING on xen/arm (me)
- don't fail on highmem CMA pages in dma_direct_alloc_pages (me)
- cleanup swiotlb initialization and share more code with swiotlb-xen
(me, Stefano Stabellini)
* tag 'dma-mapping-5.19-2022-05-25' of git://git.infradead.org/users/hch/dma-mapping: (23 commits)
dma-direct: don't over-decrypt memory
swiotlb: max mapping size takes min align mask into account
swiotlb: use the right nslabs-derived sizes in swiotlb_init_late
swiotlb: use the right nslabs value in swiotlb_init_remap
swiotlb: don't panic when the swiotlb buffer can't be allocated
dma-debug: change allocation mode from GFP_NOWAIT to GFP_ATIOMIC
dma-direct: don't fail on highmem CMA pages in dma_direct_alloc_pages
swiotlb-xen: fix DMA_ATTR_NO_KERNEL_MAPPING on arm
x86: remove cruft from <asm/dma-mapping.h>
swiotlb: remove swiotlb_init_with_tbl and swiotlb_init_late_with_tbl
swiotlb: merge swiotlb-xen initialization into swiotlb
swiotlb: provide swiotlb_init variants that remap the buffer
swiotlb: pass a gfp_mask argument to swiotlb_init_late
swiotlb: add a SWIOTLB_ANY flag to lift the low memory restriction
swiotlb: make the swiotlb_init interface more useful
x86: centralize setting SWIOTLB_FORCE when guest memory encryption is enabled
x86: remove the IOMMU table infrastructure
MIPS/octeon: use swiotlb_init instead of open coding it
arm/xen: don't check for xen_initial_domain() in xen_create_contiguous_region
swiotlb: rename swiotlb_late_init_with_default_size
...
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When running as dom0less guest (HVM domain on ARM) the xenstore event
channel is available at domain creation but the shared xenstore
interface page only becomes available later on.
In that case, wait for a notification on the xenstore event channel,
then complete the xenstore initialization later, when the shared page
is actually available.
The xenstore page has few extra field. Add them to the shared struct.
One of the field is "connection", when the connection is ready, it is
zero. If the connection is not-zero, wait for a notification.
Signed-off-by: Luca Miccio <lucmiccio@gmail.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20220513211938.719341-2-sstabellini@kernel.org
Signed-off-by: Juergen Gross <jgross@suse.com>
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There is no external user of xenbus_grant_ring() left, so merge it into
the only caller xenbus_setup_ring().
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
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Most PV device frontends share very similar code for setting up shared
ring buffers:
- allocate page(s)
- init the ring admin data
- give the backend access to the ring via grants
Tearing down the ring requires similar actions in all frontends again:
- remove grants
- free the page(s)
Provide service functions xenbus_setup_ring() and xenbus_teardown_ring()
for that purpose.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
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Instead of using a private macro for an invalid grant reference use
the common one.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Tested-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> # Arm64 only
Signed-off-by: Juergen Gross <jgross@suse.com>
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Instead of using a private macro for an invalid grant reference use
the common one.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
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Make sure a reserved grant is never put on the free list, as this could
cause hard to debug errors.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
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Update include/xen/interface/grant_table.h to its newest version.
This allows to drop some private definitions in grant-table.c and
include/xen/grant_table.h.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
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Instead of using the kernel's values for the result of PV scsi
operations use the values of the interface definition.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20220428075323.12853-3-jgross@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>
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swiotlb-xen uses very different ways to allocate coherent memory on x86
vs arm. On the former it allocates memory from the page allocator, while
on the later it reuses the dma-direct allocator the handles the
complexities of non-coherent DMA on arm platforms.
Unfortunately the complexities of trying to deal with the two cases in
the swiotlb-xen.c code lead to a bug in the handling of
DMA_ATTR_NO_KERNEL_MAPPING on arm. With the DMA_ATTR_NO_KERNEL_MAPPING
flag the coherent memory allocator does not actually allocate coherent
memory, but just a DMA handle for some memory that is DMA addressable
by the device, but which does not have to have a kernel mapping. Thus
dereferencing the return value will lead to kernel crashed and memory
corruption.
Fix this by using the dma-direct allocator directly for arm, which works
perfectly fine because on arm swiotlb-xen is only used when the domain is
1:1 mapped, and then simplifying the remaining code to only cater for the
x86 case with DMA coherent device.
Reported-by: Rahul Singh <Rahul.Singh@arm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Rahul Singh <rahul.singh@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Tested-by: Rahul Singh <rahul.singh@arm.com>
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kmap() is being deprecated and these usages are all local to the thread
so there is no reason kmap_local_page() can't be used.
Replace kmap() calls with kmap_local_page().
Signed-off-by: Alaa Mohamed <eng.alaamohamedsoliman.am@gmail.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20220419234328.10346-1-eng.alaamohamedsoliman.am@gmail.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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Reuse the generic swiotlb initialization for xen-swiotlb. For ARM/ARM64
this works trivially, while for x86 xen_swiotlb_fixup needs to be passed
as the remap argument to swiotlb_init_remap/swiotlb_init_late.
Note that the lower bound of the swiotlb size is changed to the smaller
IO_TLB_MIN_SLABS based value with this patch, but that is fine as the
2MB value used in Xen before was just an optimization and is not the
hard lower bound.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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Pass a boolean flag to indicate if swiotlb needs to be enabled based on
the addressing needs, and replace the verbose argument with a set of
flags, including one to force enable bounce buffering.
Note that this patch removes the possibility to force xen-swiotlb use
with the swiotlb=force parameter on the command line on x86 (arm and
arm64 never supported that), but this interface will be restored shortly.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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Remove the bogus Xen override that was usually larger than the actual
size and just calculate the value on demand. Note that
swiotlb_max_segment still doesn't make sense as an interface and should
eventually be removed.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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When running as a Xen PV guest use the extra memory (memory which isn't
allocated for the guest at boot time) only for ballooning purposes and
not for zone device allocations. This will remove some code without any
lack of functionality.
While at it move some code to get rid of another #ifdef.
Remove a comment which is stale since some time now.
Signed-off-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20220407093857.1485-1-jgross@suse.com
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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If a xen domain with at least two VCPUs has a PCI device attached which
enters the D3hot state during suspend, the kernel may hang while
resuming, depending on the core on which an async resume task gets
scheduled.
The bug occurs because xen's do_suspend calls dpm_resume_start while
only the timer of the boot CPU has been resumed (when xen_suspend called
syscore_resume), before calling xen_arch_suspend to resume the timers of
the other CPUs. This breaks pci_dev_d3_sleep.
Thus this patch moves the call to xen_arch_resume before the call to
dpm_resume_start, eliminating the hangs and restoring the stack-like
structure of the suspend/restore procedure.
Signed-off-by: Jakub Kądziołka <niedzejkob@invisiblethingslab.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20220323012103.2537-1-niedzejkob@invisiblethingslab.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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The gnttab_end_foreign_access() family of functions is taking a
"readonly" parameter, which isn't used. Remove it from the function
parameters.
Signed-off-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20220311103429.12845-3-jgross@suse.com
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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All grant table operations related to the "transfer" functionality
are unused currently. There have been users in the old days of the
"Xen-o-Linux" kernel, but those didn't make it upstream.
So remove the "transfer" related functions.
Signed-off-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20220311103429.12845-2-jgross@suse.com
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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Use helper macro __ATTR_RW to define HYPERVISOR_ATTR_RW to make code more clear.
Minor readability improvement.
Remove extra whitespace [boris: added this comment]
Signed-off-by: zhanglianjie <zhanglianjie@uniontech.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20220305133823.158961-1-zhanglianjie@uniontech.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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Use the helper function time_is_{before,after}_jiffies() to improve
code readability.
Signed-off-by: Wang Qing <wangqing@vivo.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/1646018104-61415-1-git-send-email-wangqing@vivo.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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gnttab_end_foreign_access() is used to free a grant reference and
optionally to free the associated page. In case the grant is still in
use by the other side processing is being deferred. This leads to a
problem in case no page to be freed is specified by the caller: the
caller doesn't know that the page is still mapped by the other side
and thus should not be used for other purposes.
The correct way to handle this situation is to take an additional
reference to the granted page in case handling is being deferred and
to drop that reference when the grant reference could be freed
finally.
This requires that there are no users of gnttab_end_foreign_access()
left directly repurposing the granted page after the call, as this
might result in clobbered data or information leaks via the not yet
freed grant reference.
This is part of CVE-2022-23041 / XSA-396.
Reported-by: Simon Gaiser <simon@invisiblethingslab.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
V4:
- expand comment in header
V5:
- get page ref in case of kmalloc() failure, too
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Instead of __get_free_pages() and free_pages() use alloc_pages_exact()
and free_pages_exact(). This is in preparation of a change of
gnttab_end_foreign_access() which will prohibit use of high-order
pages.
This is part of CVE-2022-23041 / XSA-396.
Reported-by: Simon Gaiser <simon@invisiblethingslab.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
V4:
- new patch
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Remove gnttab_query_foreign_access(), as it is unused and unsafe to
use.
All previous use cases assumed a grant would not be in use after
gnttab_query_foreign_access() returned 0. This information is useless
in best case, as it only refers to a situation in the past, which could
have changed already.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
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Using gnttab_query_foreign_access() is unsafe, as it is racy by design.
The use case in the gntalloc driver is not needed at all. While at it
replace the call of gnttab_end_foreign_access_ref() with a call of
gnttab_end_foreign_access(), which is what is really wanted there. In
case the grant wasn't used due to an allocation failure, just free the
grant via gnttab_free_grant_reference().
This is CVE-2022-23039 / part of XSA-396.
Reported-by: Demi Marie Obenour <demi@invisiblethingslab.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
V3:
- fix __del_gref() (Jan Beulich)
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Add a new grant table function gnttab_try_end_foreign_access(), which
will remove and free a grant if it is not in use.
Its main use case is to either free a grant if it is no longer in use,
or to take some other action if it is still in use. This other action
can be an error exit, or (e.g. in the case of blkfront persistent grant
feature) some special handling.
This is CVE-2022-23036, CVE-2022-23038 / part of XSA-396.
Reported-by: Demi Marie Obenour <demi@invisiblethingslab.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
V2:
- new patch
V4:
- add comments to header (Jan Beulich)
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Letting xenbus_grant_ring() tear down grants in the error case is
problematic, as the other side could already have used these grants.
Calling gnttab_end_foreign_access_ref() without checking success is
resulting in an unclear situation for any caller of xenbus_grant_ring()
as in the error case the memory pages of the ring page might be
partially mapped. Freeing them would risk unwanted foreign access to
them, while not freeing them would leak memory.
In order to remove the need to undo any gnttab_grant_foreign_access()
calls, use gnttab_alloc_grant_references() to make sure no further
error can occur in the loop granting access to the ring pages.
It should be noted that this way of handling removes leaking of
grant entries in the error case, too.
This is CVE-2022-23040 / part of XSA-396.
Reported-by: Demi Marie Obenour <demi@invisiblethingslab.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
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Replace "struct list_head head = LIST_HEAD_INIT(head)" with
"LIST_HEAD(head)" to simplify the code.
Signed-off-by: Cai Huoqing <cai.huoqing@linux.dev>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20220209032842.38818-1-cai.huoqing@linux.dev
Signed-off-by: Juergen Gross <jgross@suse.com>
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This patch implements arch_xen_unpopulated_init() on Arm where
the extended regions (if any) are gathered from DT and inserted
into specific Xen resource to be used as unused address space
for Xen scratch pages by unpopulated-alloc code.
The extended region (safe range) is a region of guest physical
address space which is unused and could be safely used to create
grant/foreign mappings instead of wasting real RAM pages from
the domain memory for establishing these mappings.
The extended regions are chosen by the hypervisor at the domain
creation time and advertised to it via "reg" property under
hypervisor node in the guest device-tree. As region 0 is reserved
for grant table space (always present), the indexes for extended
regions are 1...N.
If arch_xen_unpopulated_init() fails for some reason the default
behaviour will be restored (allocate xenballooned pages).
This patch also removes XEN_UNPOPULATED_ALLOC dependency on x86.
Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Link: https://lore.kernel.org/r/1639080336-26573-6-git-send-email-olekstysh@gmail.com
Signed-off-by: Juergen Gross <jgross@suse.com>
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The main reason of this change is that unpopulated-alloc
code cannot be used in its current form on Arm, but there
is a desire to reuse it to avoid wasting real RAM pages
for the grant/foreign mappings.
The problem is that system "iomem_resource" is used for
the address space allocation, but the really unallocated
space can't be figured out precisely by the domain on Arm
without hypervisor involvement. For example, not all device
I/O regions are known by the time domain starts creating
grant/foreign mappings. And following the advise from
"iomem_resource" we might end up reusing these regions by
a mistake. So, the hypervisor which maintains the P2M for
the domain is in the best position to provide unused regions
of guest physical address space which could be safely used
to create grant/foreign mappings.
Introduce new helper arch_xen_unpopulated_init() which purpose
is to create specific Xen resource based on the memory regions
provided by the hypervisor to be used as unused space for Xen
scratch pages. If arch doesn't define arch_xen_unpopulated_init()
the default "iomem_resource" will be used.
Update the arguments list of allocate_resource() in fill_list()
to always allocate a region from the hotpluggable range
(maximum possible addressable physical memory range for which
the linear mapping could be created). If arch doesn't define
arch_get_mappable_range() the default range (0,-1) will be used.
The behaviour on x86 won't be changed by current patch as both
arch_xen_unpopulated_init() and arch_get_mappable_range()
are not implemented for it.
Also fallback to allocate xenballooned pages (balloon out RAM
pages) if we do not have any suitable resource to work with
(target_resource is invalid) and as the result we won't be able
to provide unpopulated pages on a request.
Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Link: https://lore.kernel.org/r/1639080336-26573-5-git-send-email-olekstysh@gmail.com
Signed-off-by: Juergen Gross <jgross@suse.com>
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This patch rolls back some of the changes introduced by commit
121f2faca2c0a "xen/balloon: rename alloc/free_xenballooned_pages"
in order to make possible to still allocate xenballooned pages
if CONFIG_XEN_UNPOPULATED_ALLOC is enabled.
On Arm the unpopulated pages will be allocated on top of extended
regions provided by Xen via device-tree (the subsequent patches
will add required bits to support unpopulated-alloc feature on Arm).
The problem is that extended regions feature has been introduced
into Xen quite recently (during 4.16 release cycle). So this
effectively means that Linux must only use unpopulated-alloc on Arm
if it is running on "new Xen" which advertises these regions.
But, it will only be known after parsing the "hypervisor" node
at boot time, so before doing that we cannot assume anything.
In order to keep working if CONFIG_XEN_UNPOPULATED_ALLOC is enabled
and the extended regions are not advertised (Linux is running on
"old Xen", etc) we need the fallback to alloc_xenballooned_pages().
This way we wouldn't reduce the amount of memory usable (wasting
RAM pages) for any of the external mappings anymore (and eliminate
XSA-300) with "new Xen", but would be still functional ballooning
out RAM pages with "old Xen".
Also rename alloc(free)_xenballooned_pages to xen_alloc(free)_ballooned_pages
and make xen_alloc(free)_unpopulated_pages static inline in xen.h
if CONFIG_XEN_UNPOPULATED_ALLOC is disabled.
Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Link: https://lore.kernel.org/r/1639080336-26573-4-git-send-email-olekstysh@gmail.com
Signed-off-by: Juergen Gross <jgross@suse.com>
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If memremap_pages() succeeds the range is guaranteed to have proper page
table, there is no need for an additional virt_addr_valid() check.
Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/1639080336-26573-2-git-send-email-olekstysh@gmail.com
Signed-off-by: Juergen Gross <jgross@suse.com>
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While working with Xen's libxenvchan library I have faced an issue with
unmap notifications sent in wrong order if both UNMAP_NOTIFY_SEND_EVENT
and UNMAP_NOTIFY_CLEAR_BYTE were requested: first we send an event channel
notification and then clear the notification byte which renders in the below
inconsistency (cli_live is the byte which was requested to be cleared on unmap):
[ 444.514243] gntdev_put_map UNMAP_NOTIFY_SEND_EVENT map->notify.event 6
libxenvchan_is_open cli_live 1
[ 444.515239] __unmap_grant_pages UNMAP_NOTIFY_CLEAR_BYTE at 14
Thus it is not possible to reliably implement the checks like
- wait for the notification (UNMAP_NOTIFY_SEND_EVENT)
- check the variable (UNMAP_NOTIFY_CLEAR_BYTE)
because it is possible that the variable gets checked before it is cleared
by the kernel.
To fix that we need to re-order the notifications, so the variable is first
gets cleared and then the event channel notification is sent.
With this fix I can see the correct order of execution:
[ 54.522611] __unmap_grant_pages UNMAP_NOTIFY_CLEAR_BYTE at 14
[ 54.537966] gntdev_put_map UNMAP_NOTIFY_SEND_EVENT map->notify.event 6
libxenvchan_is_open cli_live 0
Cc: stable@vger.kernel.org
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20211210092817.580718-1-andr2000@gmail.com
Signed-off-by: Juergen Gross <jgross@suse.com>
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The Xen console driver is still vulnerable for an attack via excessive
number of events sent by the backend. Fix that by using a lateeoi event
channel.
For the normal domU initial console this requires the introduction of
bind_evtchn_to_irq_lateeoi() as there is no xenbus device available
at the time the event channel is bound to the irq.
As the decision whether an interrupt was spurious or not requires to
test for bytes having been read from the backend, move sending the
event into the if statement, as sending an event without having found
any bytes to be read is making no sense at all.
This is part of XSA-391
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
V2:
- slightly adapt spurious irq detection (Jan Beulich)
V3:
- fix spurious irq detection (Jan Beulich)
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If the xenstore page hasn't been allocated properly, reading the value
of the related hvm_param (HVM_PARAM_STORE_PFN) won't actually return
error. Instead, it will succeed and return zero. Instead of attempting
to xen_remap a bad guest physical address, detect this condition and
return early.
Note that although a guest physical address of zero for
HVM_PARAM_STORE_PFN is theoretically possible, it is not a good choice
and zero has never been validly used in that capacity.
Also recognize all bits set as an invalid value.
For 32-bit Linux, any pfn above ULONG_MAX would get truncated. Pfns
above ULONG_MAX should never be passed by the Xen tools to HVM guests
anyway, so check for this condition and return early.
Cc: stable@vger.kernel.org
Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Link: https://lore.kernel.org/r/20211123210748.1910236-1-sstabellini@kernel.org
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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The Xen pvcalls device is not essential for booting. Set the respective
flag.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20211022064800.14978-5-jgross@suse.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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When booting the xenbus driver will wait for PV devices to have
connected to their backends before continuing. The timeout is different
between essential and non-essential devices.
Non-essential devices are identified by their nodenames directly in the
xenbus driver, which requires to update this list in case a new device
type being non-essential is added (this was missed for several types
in the past).
In order to avoid this problem, add a "not_essential" flag to struct
xenbus_driver which can be set to "true" by the respective frontend.
Set this flag for the frontends currently regarded to be not essential
(vkbs and vfb) and use it for testing in the xenbus driver.
Signed-off-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20211022064800.14978-2-jgross@suse.com
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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In case of errors in xenbus_init (e.g. missing xen_store_gfn parameter),
we goto out_error but we forget to reset xen_store_domain_type to
XS_UNKNOWN. As a consequence xenbus_probe_initcall and other initcalls
will still try to initialize xenstore resulting into a crash at boot.
[ 2.479830] Call trace:
[ 2.482314] xb_init_comms+0x18/0x150
[ 2.486354] xs_init+0x34/0x138
[ 2.489786] xenbus_probe+0x4c/0x70
[ 2.498432] xenbus_probe_initcall+0x2c/0x7c
[ 2.503944] do_one_initcall+0x54/0x1b8
[ 2.507358] kernel_init_freeable+0x1ac/0x210
[ 2.511617] kernel_init+0x28/0x130
[ 2.516112] ret_from_fork+0x10/0x20
Cc: <Stable@vger.kernel.org>
Cc: jbeulich@suse.com
Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
Link: https://lore.kernel.org/r/20211115222719.2558207-1-sstabellini@kernel.org
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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This configuration option provides a misc device as an API to userspace.
Make this API usable without having to select the module as a transitive
dependency.
This also fixes an issue where localyesconfig would select
CONFIG_XEN_PRIVCMD=m because it was not visible and defaulted to
building as module.
[boris: clarified help message per Jan's suggestion]
Based-on-patch-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20211116143323.18866-1-jgross@suse.com
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip
Pull xen updates from Juergen Gross:
- a series to speed up the boot of Xen PV guests
- some cleanups in Xen related code
- replacement of license texts with the appropriate SPDX headers and
fixing of wrong SPDX headers in Xen header files
- a small series making paravirtualized interrupt masking much simpler
and at the same time removing complaints of objtool
- a fix for Xen ballooning hogging workqueues for too long
- enablement of the Xen pciback driver for Arm
- some further small fixes/enhancements
* tag 'for-linus-5.16b-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip: (22 commits)
xen/balloon: fix unused-variable warning
xen/balloon: rename alloc/free_xenballooned_pages
xen/balloon: add late_initcall_sync() for initial ballooning done
x86/xen: remove 32-bit awareness from startup_xen
xen: remove highmem remnants
xen: allow pv-only hypercalls only with CONFIG_XEN_PV
x86/xen: remove 32-bit pv leftovers
xen-pciback: allow compiling on other archs than x86
x86/xen: switch initial pvops IRQ functions to dummy ones
x86/xen: remove xen_have_vcpu_info_placement flag
x86/pvh: add prototype for xen_pvh_init()
xen: Fix implicit type conversion
xen: fix wrong SPDX headers of Xen related headers
xen/pvcalls-back: Remove redundant 'flush_workqueue()' calls
x86/xen: Remove redundant irq_enter/exit() invocations
xen-pciback: Fix return in pm_ctrl_init()
xen/x86: restrict PV Dom0 identity mapping
xen/x86: there's no highmem anymore in PV mode
xen/x86: adjust handling of the L3 user vsyscall special page table
xen/x86: adjust xen_set_fixmap()
...
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