summaryrefslogtreecommitdiff
path: root/arch/x86/kvm/vmx/vmx.h
diff options
context:
space:
mode:
authorPawan Gupta <pawan.kumar.gupta@linux.intel.com>2022-05-19 20:35:15 -0700
committerBorislav Petkov <bp@suse.de>2022-05-21 12:41:35 +0200
commit027bbb884be006b05d9c577d6401686053aa789e (patch)
treeb60942dd17dc33f97ae5c81cd972b96100283d18 /arch/x86/kvm/vmx/vmx.h
parenta992b8a4682f119ae035a01b40d4d0665c4a2875 (diff)
KVM: x86/speculation: Disable Fill buffer clear within guests
The enumeration of MD_CLEAR in CPUID(EAX=7,ECX=0).EDX{bit 10} is not an accurate indicator on all CPUs of whether the VERW instruction will overwrite fill buffers. FB_CLEAR enumeration in IA32_ARCH_CAPABILITIES{bit 17} covers the case of CPUs that are not vulnerable to MDS/TAA, indicating that microcode does overwrite fill buffers. Guests running in VMM environments may not be aware of all the capabilities/vulnerabilities of the host CPU. Specifically, a guest may apply MDS/TAA mitigations when a virtual CPU is enumerated as vulnerable to MDS/TAA even when the physical CPU is not. On CPUs that enumerate FB_CLEAR_CTRL the VMM may set FB_CLEAR_DIS to skip overwriting of fill buffers by the VERW instruction. This is done by setting FB_CLEAR_DIS during VMENTER and resetting on VMEXIT. For guests that enumerate FB_CLEAR (explicitly asking for fill buffer clear capability) the VMM will not use FB_CLEAR_DIS. Irrespective of guest state, host overwrites CPU buffers before VMENTER to protect itself from an MMIO capable guest, as part of mitigation for MMIO Stale Data vulnerabilities. Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> Signed-off-by: Borislav Petkov <bp@suse.de>
Diffstat (limited to 'arch/x86/kvm/vmx/vmx.h')
-rw-r--r--arch/x86/kvm/vmx/vmx.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index b98c7e96697a..8d2342ede0c5 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -348,6 +348,8 @@ struct vcpu_vmx {
u64 msr_ia32_feature_control_valid_bits;
/* SGX Launch Control public key hash */
u64 msr_ia32_sgxlepubkeyhash[4];
+ u64 msr_ia32_mcu_opt_ctrl;
+ bool disable_fb_clear;
struct pt_desc pt_desc;
struct lbr_desc lbr_desc;