On Sun, Jan 23, 2022, Like Xu wrote:
> From: Like Xu <likexu@xxxxxxxxxxx>
>
> XCR0 is reset to 1 by RESET but not INIT and IA32_XSS is zeroed by
> both RESET and INIT. The kvm_set_msr_common()'s handling of MSR_IA32_XSS
> also needs to update kvm_update_cpuid_runtime(). In the above cases, the
> size in bytes of the XSAVE area containing all states enabled by XCR0 or
> (XCRO | IA32_XSS) needs to be updated.
>
> For simplicity and consistency, existing helpers are used to write values
> and call kvm_update_cpuid_runtime(), and it's not exactly a fast path.
>
> Fixes: a554d207dc46 ("KVM: X86: Processor States following Reset or INIT")
> Signed-off-by: Like Xu <likexu@xxxxxxxxxxx>
> ---
> v2 -> v3 Changelog:
> - Apply s/legacy/existing in the commit message; (Sean)
> - Invoke kvm_update_cpuid_runtime() for MSR_IA32_XSS; (Sean)
>
> arch/x86/kvm/x86.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 55518b7d3b96..4b509b26d9ab 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3535,6 +3535,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct
> msr_data *msr_info)
> if (data & ~supported_xss)
> return 1;
> vcpu->arch.ia32_xss = data;
> + kvm_update_cpuid_runtime(vcpu);
> break;
> case MSR_SMI_COUNT:
> if (!msr_info->host_initiated)
> @@ -11256,7 +11257,7 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
>
> vcpu->arch.msr_misc_features_enables = 0;
>
> - vcpu->arch.xcr0 = XFEATURE_MASK_FP;
> + __kvm_set_xcr(vcpu, 0, XFEATURE_MASK_FP);
> }
>
> /* All GPRs except RDX (handled below) are zeroed on RESET/INIT. */
> @@ -11273,7 +11274,7 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
> cpuid_0x1 = kvm_find_cpuid_entry(vcpu, 1, 0);
> kvm_rdx_write(vcpu, cpuid_0x1 ? cpuid_0x1->eax : 0x600);
>
> - vcpu->arch.ia32_xss = 0;
> + __kvm_set_msr(vcpu, MSR_IA32_XSS, 0, true);
Heh, this now conflicts with a patch Xiaoyao just posted, turns out the SDM was
wrong. I think there's also some whitespace change or something that prevents
this from applying cleanly. For convenience, I'll post a miniseries with this
and Xiaoyao's patch.
[*] https://lore.kernel.org/all/20220126034750.2495371-1-xiaoyao.li@xxxxxxxxx
>
> static_call(kvm_x86_vcpu_reset)(vcpu, init_event);
>
> --
> 2.33.1
>
>
