From: Sean Christopherson <seanjc@google.com>
To: John Allen <john.allen@amd.com>
Cc: kvm@vger.kernel.org, weijiang.yang@intel.com,
rick.p.edgecombe@intel.com, thomas.lendacky@amd.com,
bp@alien8.de, pbonzini@redhat.com, mlevitsk@redhat.com,
linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH v2 9/9] KVM: SVM: Add CET features to supported_xss
Date: Wed, 1 May 2024 16:47:53 -0700 [thread overview]
Message-ID: <ZjLUqaDbRglCCnD7@google.com> (raw)
In-Reply-To: <20240226213244.18441-10-john.allen@amd.com>
On Mon, Feb 26, 2024, John Allen wrote:
> If the CPU supports CET, add CET XSAVES feature bits to the
> supported_xss mask.
>
> Signed-off-by: John Allen <john.allen@amd.com>
> ---
> arch/x86/kvm/svm/svm.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 1181f017c173..d97d82ebec4a 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -5177,6 +5177,10 @@ static __init void svm_set_cpu_caps(void)
> boot_cpu_has(X86_FEATURE_AMD_SSBD))
> kvm_cpu_cap_set(X86_FEATURE_VIRT_SSBD);
>
> + if (kvm_cpu_cap_has(X86_FEATURE_SHSTK))
> + kvm_caps.supported_xss |= XFEATURE_MASK_CET_USER |
> + XFEATURE_MASK_CET_KERNEL;
Based on Weijiang's series, I believe this is unnecessary. Common x86 code will
both set supported_xss, and clear bits if their associated features are unsupported.
I also asked Weijiang to modify the "advertise to userspace" patch to explicitly
clear SHSTK and IBT in svm_set_cpu_caps()[*], so if the stars align as I think they
will, this patch should simply need to delete the
kvm_cpu_cap_clear(X86_FEATURE_SHSTK);
that will be added by the VMX series.
[*] https://lore.kernel.org/all/ZjLRnisdUgeYgg8i@google.com
prev parent reply other threads:[~2024-05-01 23:47 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-26 21:32 [PATCH v2 0/9] SVM guest shadow stack support John Allen
2024-02-26 21:32 ` [PATCH v2 1/9] x86/boot: Move boot_*msr helpers to asm/shared/msr.h John Allen
2024-02-27 19:45 ` Borislav Petkov
2024-02-26 21:32 ` [PATCH v2 2/9] KVM: x86: SVM: Emulate reads and writes to shadow stack MSRs John Allen
2024-02-26 21:32 ` [PATCH v2 3/9] KVM: x86: SVM: Update dump_vmcb with shadow stack save area additions John Allen
2024-02-26 21:32 ` [PATCH v2 4/9] KVM: x86: SVM: Pass through shadow stack MSRs John Allen
2024-02-26 21:32 ` [PATCH v2 5/9] KVM: SVM: Rename vmplX_ssp -> plX_ssp John Allen
2024-02-27 18:14 ` Sean Christopherson
2024-02-27 19:15 ` Tom Lendacky
2024-02-27 19:19 ` John Allen
2024-02-27 19:23 ` Sean Christopherson
2024-02-27 19:25 ` John Allen
2024-02-26 21:32 ` [PATCH v2 6/9] KVM: SVM: Add MSR_IA32_XSS to the GHCB for hypervisor kernel John Allen
2024-05-01 23:43 ` Sean Christopherson
2024-05-02 17:46 ` Tom Lendacky
2024-05-02 18:34 ` Sean Christopherson
2024-02-26 21:32 ` [PATCH v2 7/9] x86/sev-es: Include XSS value in GHCB CPUID request John Allen
2024-02-27 19:47 ` Borislav Petkov
2024-02-26 21:32 ` [PATCH v2 8/9] KVM: SVM: Use KVM-governed features to track SHSTK John Allen
2024-02-26 21:32 ` [PATCH v2 9/9] KVM: SVM: Add CET features to supported_xss John Allen
2024-05-01 23:47 ` Sean Christopherson [this message]
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