diff options
| author | Oliver Upton <oupton@google.com> | 2020-08-18 15:24:28 +0000 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2020-10-21 17:36:32 -0400 |
| commit | 66570e966dd9cb4fd57811d0056c6472a14a2c41 (patch) | |
| tree | 06172486c1b55c545ea71bc0cd23c288c7b19fd1 /Documentation | |
| parent | 210dfd93ea3dc63e8c21b75ddd909447341f6382 (diff) | |
kvm: x86: only provide PV features if enabled in guest's CPUID
KVM unconditionally provides PV features to the guest, regardless of the
configured CPUID. An unwitting guest that doesn't check
KVM_CPUID_FEATURES before use could access paravirt features that
userspace did not intend to provide. Fix this by checking the guest's
CPUID before performing any paravirtual operations.
Introduce a capability, KVM_CAP_ENFORCE_PV_FEATURE_CPUID, to gate the
aforementioned enforcement. Migrating a VM from a host w/o this patch to
a host with this patch could silently change the ABI exposed to the
guest, warranting that we default to the old behavior and opt-in for
the new one.
Reviewed-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Signed-off-by: Oliver Upton <oupton@google.com>
Change-Id: I202a0926f65035b872bfe8ad15307c026de59a98
Message-Id: <20200818152429.1923996-4-oupton@google.com>
Reviewed-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/virt/kvm/api.rst | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 9ece9a827a58..76317221d29f 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6380,3 +6380,14 @@ ranges that KVM should reject access to. In combination with KVM_CAP_X86_USER_SPACE_MSR, this allows user space to trap and emulate MSRs that are outside of the scope of KVM as well as limit the attack surface on KVM's MSR emulation code. + + +8.26 KVM_CAP_ENFORCE_PV_CPUID +----------------------------- + +Architectures: x86 + +When enabled, KVM will disable paravirtual features provided to the +guest according to the bits in the KVM_CPUID_FEATURES CPUID leaf +(0x40000001). Otherwise, a guest may use the paravirtual features +regardless of what has actually been exposed through the CPUID leaf. |