On Thu, Jul 16, 2020 at 11:16:21AM +0800, Yang Weijiang wrote:
> CPUID(0xd, 1) reports the current required storage size of XCR0 | XSS,
> when guest updates the XSS, it's necessary to update the CPUID leaf, otherwise
> guest will fetch old state size, and results to some WARN traces during guest
> running.
>
> supported_xss is initialized to host_xss & KVM_SUPPORTED_XSS to indicate
> current
> MSR_IA32_XSS bits supported in KVM, but actual XSS bits seen in guest depends
> on the setting of CPUID(0xd,1).{ECX, EDX} for guest.
>
> Co-developed-by: Zhang Yi Z <[email protected]>
> Signed-off-by: Zhang Yi Z <[email protected]>
> Signed-off-by: Yang Weijiang <[email protected]>
> ---
> arch/x86/include/asm/kvm_host.h | 1 +
> arch/x86/kvm/cpuid.c | 23 +++++++++++++++++++----
> arch/x86/kvm/x86.c | 12 ++++++++----
> 3 files changed, 28 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index be5363b21540..e8c749596ba2 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -654,6 +654,7 @@ struct kvm_vcpu_arch {
>
> u64 xcr0;
> u64 guest_supported_xcr0;
> + u64 guest_supported_xss;
>
> struct kvm_pio_request pio;
> void *pio_data;
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 8a294f9747aa..d97b2a6e8a8c 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -88,14 +88,29 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
> vcpu->arch.guest_supported_xcr0 = 0;
> } else {
> vcpu->arch.guest_supported_xcr0 =
> - (best->eax | ((u64)best->edx << 32)) & supported_xcr0;
> + (((u64)best->edx << 32) | best->eax) & supported_xcr0;
While I don't necessarily disagree with the change, it doesn't belong in
this patch.
> best->ebx = xstate_required_size(vcpu->arch.xcr0, false);
> }
>
> best = kvm_find_cpuid_entry(vcpu, 0xD, 1);
> - if (best && (cpuid_entry_has(best, X86_FEATURE_XSAVES) ||
> - cpuid_entry_has(best, X86_FEATURE_XSAVEC)))
> - best->ebx = xstate_required_size(vcpu->arch.xcr0, true);
> + if (best) {
> + if (cpuid_entry_has(best, X86_FEATURE_XSAVES) ||
> + cpuid_entry_has(best, X86_FEATURE_XSAVEC)) {
> + u64 xstate = vcpu->arch.xcr0 | vcpu->arch.ia32_xss;
> +
> + best->ebx = xstate_required_size(xstate, true);
> + }
> +
> + if (!cpuid_entry_has(best, X86_FEATURE_XSAVES)) {
> + best->ecx = 0;
> + best->edx = 0;
> + }
> + vcpu->arch.guest_supported_xss =
> + (((u64)best->edx << 32) | best->ecx) & supported_xss;
> +
> + } else {
> + vcpu->arch.guest_supported_xss = 0;
> + }
>
> /*
> * The existing code assumes virtual address is 48-bit or 57-bit in the
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 906e07039d59..8aed32ff9c0c 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2912,9 +2912,12 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct
> msr_data *msr_info)
> * IA32_XSS[bit 8]. Guests have to use RDMSR/WRMSR rather than
> * XSAVES/XRSTORS to save/restore PT MSRs.
> */
> - if (data & ~supported_xss)
> + if (data & ~vcpu->arch.guest_supported_xss)
> return 1;
> - vcpu->arch.ia32_xss = data;
> + if (vcpu->arch.ia32_xss != data) {
> + vcpu->arch.ia32_xss = data;
> + kvm_update_cpuid(vcpu);
> + }
> break;
> case MSR_SMI_COUNT:
> if (!msr_info->host_initiated)
> @@ -9779,8 +9782,9 @@ int kvm_arch_hardware_setup(void *opaque)
>
> memcpy(&kvm_x86_ops, ops->runtime_ops, sizeof(kvm_x86_ops));
>
> - if (!kvm_cpu_cap_has(X86_FEATURE_XSAVES))
> - supported_xss = 0;
> + supported_xss = 0;
> + if (kvm_cpu_cap_has(X86_FEATURE_XSAVES))
> + supported_xss = host_xss & KVM_SUPPORTED_XSS;
Updating supported_xss in the actual enabling patch.
>
> #define __kvm_cpu_cap_has(UNUSED_, f) kvm_cpu_cap_has(f)
> cr4_reserved_bits = __cr4_reserved_bits(__kvm_cpu_cap_has, UNUSED_);
> --
> 2.17.2
>
