From: Borislav Petkov <bp@alien8.de>
To: John Allen <john.allen@amd.com>
Cc: kvm@vger.kernel.org, weijiang.yang@intel.com,
rick.p.edgecombe@intel.com, seanjc@google.com,
thomas.lendacky@amd.com, pbonzini@redhat.com,
mlevitsk@redhat.com, linux-kernel@vger.kernel.org,
x86@kernel.org
Subject: Re: [PATCH v2 7/9] x86/sev-es: Include XSS value in GHCB CPUID request
Date: Tue, 27 Feb 2024 20:47:47 +0100 [thread overview]
Message-ID: <20240227194747.GFZd48Y6dzDY0dVObV@fat_crate.local> (raw)
In-Reply-To: <20240226213244.18441-8-john.allen@amd.com>
On Mon, Feb 26, 2024 at 09:32:42PM +0000, John Allen wrote:
> When a guest issues a cpuid instruction for Fn0000000D_x0B
> (CetUserOffset), the hypervisor may intercept and access the guest XSS
> value. For SEV-ES, this is encrypted and needs to be included in the
> GHCB to be visible to the hypervisor. The rdmsr instruction needs to be
> called directly as the code may be used in early boot in which case the
> rdmsr wrappers should be avoided as they are incompatible with the
> decompression boot phase.
>
> Signed-off-by: John Allen <john.allen@amd.com>
> ---
> v2:
> - Use raw_rdmsr instead of calling rdmsr directly.
> ---
> arch/x86/kernel/sev-shared.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
> index 1d24ec679915..10ac130cc953 100644
> --- a/arch/x86/kernel/sev-shared.c
> +++ b/arch/x86/kernel/sev-shared.c
> @@ -966,6 +966,13 @@ static enum es_result vc_handle_cpuid(struct ghcb *ghcb,
> /* xgetbv will cause #GP - use reset value for xcr0 */
> ghcb_set_xcr0(ghcb, 1);
>
> + if (has_cpuflag(X86_FEATURE_SHSTK) && regs->ax == 0xd && regs->cx <= 1) {
> + struct msr m;
> +
> + raw_rdmsr(MSR_IA32_XSS, &m);
> + ghcb_set_xss(ghcb, m.q);
> + }
> +
> ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_CPUID, 0, 0);
> if (ret != ES_OK)
> return ret;
> --
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2024-02-27 19:48 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 [this message]
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
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