diff options
Diffstat (limited to 'Documentation/virt/kvm')
| -rw-r--r-- | Documentation/virt/kvm/api.rst | 73 | ||||
| -rw-r--r-- | Documentation/virt/kvm/locking.rst | 11 |
2 files changed, 42 insertions, 42 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index bae90f3cd11d..158d1186d103 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -1574,8 +1574,8 @@ This ioctl would set vcpu's xcr to the value userspace specified. }; #define KVM_CPUID_FLAG_SIGNIFCANT_INDEX BIT(0) - #define KVM_CPUID_FLAG_STATEFUL_FUNC BIT(1) - #define KVM_CPUID_FLAG_STATE_READ_NEXT BIT(2) + #define KVM_CPUID_FLAG_STATEFUL_FUNC BIT(1) /* deprecated */ + #define KVM_CPUID_FLAG_STATE_READ_NEXT BIT(2) /* deprecated */ struct kvm_cpuid_entry2 { __u32 function; @@ -1626,13 +1626,6 @@ emulate them efficiently. The fields in each entry are defined as follows: KVM_CPUID_FLAG_SIGNIFCANT_INDEX: if the index field is valid - KVM_CPUID_FLAG_STATEFUL_FUNC: - if cpuid for this function returns different values for successive - invocations; there will be several entries with the same function, - all with this flag set - KVM_CPUID_FLAG_STATE_READ_NEXT: - for KVM_CPUID_FLAG_STATEFUL_FUNC entries, set if this entry is - the first entry to be read by a cpu eax, ebx, ecx, edx: the values returned by the cpuid instruction for @@ -3349,8 +3342,8 @@ The member 'flags' is used for passing flags from userspace. :: #define KVM_CPUID_FLAG_SIGNIFCANT_INDEX BIT(0) - #define KVM_CPUID_FLAG_STATEFUL_FUNC BIT(1) - #define KVM_CPUID_FLAG_STATE_READ_NEXT BIT(2) + #define KVM_CPUID_FLAG_STATEFUL_FUNC BIT(1) /* deprecated */ + #define KVM_CPUID_FLAG_STATE_READ_NEXT BIT(2) /* deprecated */ struct kvm_cpuid_entry2 { __u32 function; @@ -3396,13 +3389,6 @@ The fields in each entry are defined as follows: KVM_CPUID_FLAG_SIGNIFCANT_INDEX: if the index field is valid - KVM_CPUID_FLAG_STATEFUL_FUNC: - if cpuid for this function returns different values for successive - invocations; there will be several entries with the same function, - all with this flag set - KVM_CPUID_FLAG_STATE_READ_NEXT: - for KVM_CPUID_FLAG_STATEFUL_FUNC entries, set if this entry is - the first entry to be read by a cpu eax, ebx, ecx, edx: @@ -4613,35 +4599,38 @@ unpins the VPA pages and releases all the device pages that are used to track the secure pages by hypervisor. 4.122 KVM_S390_NORMAL_RESET +--------------------------- -Capability: KVM_CAP_S390_VCPU_RESETS -Architectures: s390 -Type: vcpu ioctl -Parameters: none -Returns: 0 +:Capability: KVM_CAP_S390_VCPU_RESETS +:Architectures: s390 +:Type: vcpu ioctl +:Parameters: none +:Returns: 0 This ioctl resets VCPU registers and control structures according to the cpu reset definition in the POP (Principles Of Operation). 4.123 KVM_S390_INITIAL_RESET +---------------------------- -Capability: none -Architectures: s390 -Type: vcpu ioctl -Parameters: none -Returns: 0 +:Capability: none +:Architectures: s390 +:Type: vcpu ioctl +:Parameters: none +:Returns: 0 This ioctl resets VCPU registers and control structures according to the initial cpu reset definition in the POP. However, the cpu is not put into ESA mode. This reset is a superset of the normal reset. 4.124 KVM_S390_CLEAR_RESET +-------------------------- -Capability: KVM_CAP_S390_VCPU_RESETS -Architectures: s390 -Type: vcpu ioctl -Parameters: none -Returns: 0 +:Capability: KVM_CAP_S390_VCPU_RESETS +:Architectures: s390 +:Type: vcpu ioctl +:Parameters: none +:Returns: 0 This ioctl resets VCPU registers and control structures according to the clear cpu reset definition in the POP. However, the cpu is not put @@ -5754,8 +5743,13 @@ and injected exceptions. :Architectures: x86, arm, arm64, mips :Parameters: args[0] whether feature should be enabled or not -With this capability enabled, KVM_GET_DIRTY_LOG will not automatically -clear and write-protect all pages that are returned as dirty. +Valid flags are:: + + #define KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE (1 << 0) + #define KVM_DIRTY_LOG_INITIALLY_SET (1 << 1) + +With KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE is set, KVM_GET_DIRTY_LOG will not +automatically clear and write-protect all pages that are returned as dirty. Rather, userspace will have to do this operation separately using KVM_CLEAR_DIRTY_LOG. @@ -5766,12 +5760,19 @@ than requiring to sync a full memslot; this ensures that KVM does not take spinlocks for an extended period of time. Second, in some cases a large amount of time can pass between a call to KVM_GET_DIRTY_LOG and userspace actually using the data in the page. Pages can be modified -during this time, which is inefficint for both the guest and userspace: +during this time, which is inefficient for both the guest and userspace: the guest will incur a higher penalty due to write protection faults, while userspace can see false reports of dirty pages. Manual reprotection helps reducing this time, improving guest performance and reducing the number of dirty log false positives. +With KVM_DIRTY_LOG_INITIALLY_SET set, all the bits of the dirty bitmap +will be initialized to 1 when created. This also improves performance because +dirty logging can be enabled gradually in small chunks on the first call +to KVM_CLEAR_DIRTY_LOG. KVM_DIRTY_LOG_INITIALLY_SET depends on +KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE (it is also only available on +x86 for now). + KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 was previously available under the name KVM_CAP_MANUAL_DIRTY_LOG_PROTECT, but the implementation had bugs that make it hard or impossible to use it correctly. The availability of diff --git a/Documentation/virt/kvm/locking.rst b/Documentation/virt/kvm/locking.rst index c02291beac3f..b21a34c34a21 100644 --- a/Documentation/virt/kvm/locking.rst +++ b/Documentation/virt/kvm/locking.rst @@ -96,19 +96,18 @@ will happen: We dirty-log for gfn1, that means gfn2 is lost in dirty-bitmap. For direct sp, we can easily avoid it since the spte of direct sp is fixed -to gfn. For indirect sp, before we do cmpxchg, we call gfn_to_pfn_atomic() -to pin gfn to pfn, because after gfn_to_pfn_atomic(): +to gfn. For indirect sp, we disabled fast page fault for simplicity. + +A solution for indirect sp could be to pin the gfn, for example via +kvm_vcpu_gfn_to_pfn_atomic, before the cmpxchg. After the pinning: - We have held the refcount of pfn that means the pfn can not be freed and be reused for another gfn. -- The pfn is writable that means it can not be shared between different gfns +- The pfn is writable and therefore it cannot be shared between different gfns by KSM. Then, we can ensure the dirty bitmaps is correctly set for a gfn. -Currently, to simplify the whole things, we disable fast page fault for -indirect shadow page. - 2) Dirty bit tracking In the origin code, the spte can be fast updated (non-atomically) if the |