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Diffstat (limited to 'Documentation/virt')
| -rw-r--r-- | Documentation/virt/kvm/api.rst | 107 |
1 files changed, 105 insertions, 2 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index fd4a84911355..56c6fca6219f 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -1495,7 +1495,8 @@ Fails if any VCPU has already been created. Define which vcpu is the Bootstrap Processor (BSP). Values are the same as the vcpu id in KVM_CREATE_VCPU. If this ioctl is not called, the default -is vcpu 0. +is vcpu 0. This ioctl has to be called before vcpu creation, +otherwise it will return EBUSY error. 4.42 KVM_GET_XSAVE @@ -4786,7 +4787,109 @@ KVM_PV_VM_VERIFY Verify the integrity of the unpacked image. Only if this succeeds, KVM is allowed to start protected VCPUs. -4.126 KVM_XEN_HVM_SET_ATTR +4.126 KVM_X86_SET_MSR_FILTER +---------------------------- + +:Capability: KVM_X86_SET_MSR_FILTER +:Architectures: x86 +:Type: vm ioctl +:Parameters: struct kvm_msr_filter +:Returns: 0 on success, < 0 on error + +:: + + struct kvm_msr_filter_range { + #define KVM_MSR_FILTER_READ (1 << 0) + #define KVM_MSR_FILTER_WRITE (1 << 1) + __u32 flags; + __u32 nmsrs; /* number of msrs in bitmap */ + __u32 base; /* MSR index the bitmap starts at */ + __u8 *bitmap; /* a 1 bit allows the operations in flags, 0 denies */ + }; + + #define KVM_MSR_FILTER_MAX_RANGES 16 + struct kvm_msr_filter { + #define KVM_MSR_FILTER_DEFAULT_ALLOW (0 << 0) + #define KVM_MSR_FILTER_DEFAULT_DENY (1 << 0) + __u32 flags; + struct kvm_msr_filter_range ranges[KVM_MSR_FILTER_MAX_RANGES]; + }; + +flags values for ``struct kvm_msr_filter_range``: + +``KVM_MSR_FILTER_READ`` + + Filter read accesses to MSRs using the given bitmap. A 0 in the bitmap + indicates that a read should immediately fail, while a 1 indicates that + a read for a particular MSR should be handled regardless of the default + filter action. + +``KVM_MSR_FILTER_WRITE`` + + Filter write accesses to MSRs using the given bitmap. A 0 in the bitmap + indicates that a write should immediately fail, while a 1 indicates that + a write for a particular MSR should be handled regardless of the default + filter action. + +``KVM_MSR_FILTER_READ | KVM_MSR_FILTER_WRITE`` + + Filter both read and write accesses to MSRs using the given bitmap. A 0 + in the bitmap indicates that both reads and writes should immediately fail, + while a 1 indicates that reads and writes for a particular MSR are not + filtered by this range. + +flags values for ``struct kvm_msr_filter``: + +``KVM_MSR_FILTER_DEFAULT_ALLOW`` + + If no filter range matches an MSR index that is getting accessed, KVM will + fall back to allowing access to the MSR. + +``KVM_MSR_FILTER_DEFAULT_DENY`` + + If no filter range matches an MSR index that is getting accessed, KVM will + fall back to rejecting access to the MSR. In this mode, all MSRs that should + be processed by KVM need to explicitly be marked as allowed in the bitmaps. + +This ioctl allows user space to define up to 16 bitmaps of MSR ranges to +specify whether a certain MSR access should be explicitly filtered for or not. + +If this ioctl has never been invoked, MSR accesses are not guarded and the +default KVM in-kernel emulation behavior is fully preserved. + +Calling this ioctl with an empty set of ranges (all nmsrs == 0) disables MSR +filtering. In that mode, ``KVM_MSR_FILTER_DEFAULT_DENY`` is invalid and causes +an error. + +As soon as the filtering is in place, every MSR access is processed through +the filtering except for accesses to the x2APIC MSRs (from 0x800 to 0x8ff); +x2APIC MSRs are always allowed, independent of the ``default_allow`` setting, +and their behavior depends on the ``X2APIC_ENABLE`` bit of the APIC base +register. + +If a bit is within one of the defined ranges, read and write accesses are +guarded by the bitmap's value for the MSR index if the kind of access +is included in the ``struct kvm_msr_filter_range`` flags. If no range +cover this particular access, the behavior is determined by the flags +field in the kvm_msr_filter struct: ``KVM_MSR_FILTER_DEFAULT_ALLOW`` +and ``KVM_MSR_FILTER_DEFAULT_DENY``. + +Each bitmap range specifies a range of MSRs to potentially allow access on. +The range goes from MSR index [base .. base+nmsrs]. The flags field +indicates whether reads, writes or both reads and writes are filtered +by setting a 1 bit in the bitmap for the corresponding MSR index. + +If an MSR access is not permitted through the filtering, it generates a +#GP inside the guest. When combined with KVM_CAP_X86_USER_SPACE_MSR, that +allows user space to deflect and potentially handle various MSR accesses +into user space. + +Note, invoking this ioctl with a vCPU is running is inherently racy. However, +KVM does guarantee that vCPUs will see either the previous filter or the new +filter, e.g. MSRs with identical settings in both the old and new filter will +have deterministic behavior. + +4.127 KVM_XEN_HVM_SET_ATTR -------------------------- :Capability: KVM_CAP_XEN_HVM / KVM_XEN_HVM_CONFIG_SHARED_INFO |