[PATCH v2 1/2] KVM: x86: fix documentation for KVM_X86_SET_MSR_FILTER

Aaron Lewis
2022-07-12T00:10:55Z

Two copies of KVM_X86_SET_MSR_FILTER somehow managed to make it's way
into the documentation. Remove one copy and merge the difference from
the removed copy into the copy that's being kept.

Fixes: fd49e8ee70b3 ("Merge branch 'kvm-sev-cgroup' into HEAD")
Signed-off-by: Aaron Lewis <aaronlewis@google.com>
---
Documentation/virt/kvm/api.rst | 115 +++------------------------------
1 file changed, 8 insertions(+), 107 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index bafaeedd455c..5c651a4e4e2c 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -4074,7 +4074,7 @@ Queues an SMI on the thread's vcpu.
4.97 KVM_X86_SET_MSR_FILTER
----------------------------

-:Capability: KVM_X86_SET_MSR_FILTER
+:Capability: KVM_CAP_X86_MSR_FILTER
:Architectures: x86
:Type: vm ioctl
:Parameters: struct kvm_msr_filter
@@ -4173,8 +4173,12 @@ If an MSR access is not permitted through the filtering, it generates a
allows user space to deflect and potentially handle various MSR accesses
into user space.

-If a vCPU is in running state while this ioctl is invoked, the vCPU may
-experience inconsistent filtering behavior on MSR accesses.
+Note, invoking this ioctl while 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.
+
+

4.98 KVM_CREATE_SPAPR_TCE_64
----------------------------
@@ -5287,110 +5291,7 @@ KVM_PV_DUMP
authentication tag all of which are needed to decrypt the dump at a
later time.

-
-4.126 KVM_X86_SET_MSR_FILTER
-----------------------------
-
-:Capability: KVM_CAP_X86_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
+4.126 KVM_XEN_HVM_SET_ATTR
--------------------------

:Capability: KVM_CAP_XEN_HVM / KVM_XEN_HVM_CONFIG_SHARED_INFO
--
2.37.0.144.g8ac04bfd2-goog