On Wed, May 03, 2023, Mingwei Zhang wrote:
> Add MSR_IA32_TSX_CTRL into msrs_to_save[] to explicitly tell userspace to
> save/restore the register value during migration. Missing this may cause
> userspace that relies on KVM ioctl(KVM_GET_MSR_INDEX_LIST) fail to port the
> value to the target VM.
>
> Fixes: b07a5c53d42a ("KVM: vmx: use MSR_IA32_TSX_CTRL to hard-disable TSX on guest that lack it")
> Reported-by: Jim Mattson <jmattson@xxxxxxxxxx>
> Signed-off-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
> ---
> arch/x86/kvm/x86.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 237c483b1230..2236cfee4b7a 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1431,7 +1431,7 @@ static const u32 msrs_to_save_base[] = {
> #endif
> MSR_IA32_TSC, MSR_IA32_CR_PAT, MSR_VM_HSAVE_PA,
> MSR_IA32_FEAT_CTL, MSR_IA32_BNDCFGS, MSR_TSC_AUX,
> - MSR_IA32_SPEC_CTRL,
> + MSR_IA32_SPEC_CTRL, MSR_IA32_TSX_CTRL,
> MSR_IA32_RTIT_CTL, MSR_IA32_RTIT_STATUS, MSR_IA32_RTIT_CR3_MATCH,
> MSR_IA32_RTIT_OUTPUT_BASE, MSR_IA32_RTIT_OUTPUT_MASK,
> MSR_IA32_RTIT_ADDR0_A, MSR_IA32_RTIT_ADDR0_B,
> --
Hmm, KVM shouldn't report the MSR if it can't be written by the guest. Over-
reporting won't cause functional issues, and the odds of the MSR existing but not
being reported in ARCH_CAPILIBITES are basically zilch, but IMO it's worth adding
the check if only to document when the MSRs is fully supported.
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e7f78fe79b32..d8608c6753ff 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7152,6 +7152,10 @@ static void kvm_probe_msr_to_save(u32 msr_index)
if (!kvm_cpu_cap_has(X86_FEATURE_XFD))
return;
break;
+ case MSR_IA32_TSX_CTRL:
+ if (!(kvm_get_arch_capabilities() & ARCH_CAP_TSX_CTRL_MSR))
+ return;
+ break;
default:
break;
}
