From: Chao Gao <chao.gao@intel.com>
To: John Allen <john.allen@amd.com>
Cc: <kvm@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<x86@kernel.org>, <seanjc@google.com>, <pbonzini@redhat.com>,
<dave.hansen@intel.com>, <rick.p.edgecombe@intel.com>,
<mlevitsk@redhat.com>, <weijiang.yang@intel.com>, <bp@alien8.de>,
<dave.hansen@linux.intel.com>, <hpa@zytor.com>,
<mingo@redhat.com>, <tglx@linutronix.de>,
<thomas.lendacky@amd.com>
Subject: Re: [PATCH v3 5/5] KVM: SVM: Enable shadow stack virtualization for SVM
Date: Sat, 6 Sep 2025 04:50:45 +0800 [thread overview]
Message-ID: <aLtNJZo2o/i9AyqX@intel.com> (raw)
In-Reply-To: <aLissKgzL8fX+tXr@AUSJOHALLEN.amd.com>
>> >- /* KVM doesn't yet support CET virtualization for SVM. */
>> >- kvm_cpu_cap_clear(X86_FEATURE_SHSTK);
>> >- kvm_cpu_cap_clear(X86_FEATURE_IBT);
>>
>> IIUC, IBT should be cleared because KVM doesn't support IBT for SVM.
>
>Yeah, I wondered about this. The reason I chose to not clear this is
>because we don't explicitly clear other features that are not supported
>on AMD hardware AFAICT.
Your series doesn't enable IBT for SVM. If future AMD CPUs add IBT support,
this KVM running on those CPUs will inadvertently advertise IBT support.
>Is there a reason we should clear this and not
>other unsupported features?
I think they should be cleared if they require any KVM enabling beyond just
adding the CPUID bits. At the very least, we can handle IBT correctly.
prev parent reply other threads:[~2025-09-05 20:51 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-06 20:45 [PATCH v3 0/5] Enable Shadow Stack Virtualization " John Allen
2025-08-06 20:45 ` [PATCH v3 1/5] KVM: x86: SVM: Emulate reads and writes to shadow stack MSRs John Allen
2025-08-25 1:27 ` Chao Gao
2025-08-06 20:45 ` [PATCH v3 2/5] KVM: x86: SVM: Update dump_vmcb with shadow stack save area additions John Allen
2025-08-22 20:57 ` Tom Lendacky
2025-08-06 20:45 ` [PATCH v3 3/5] KVM: x86: SVM: Pass through shadow stack MSRs John Allen
2025-08-25 1:21 ` Chao Gao
2025-08-06 20:45 ` [PATCH v3 4/5] KVM: SVM: Add MSR_IA32_XSS to the GHCB for hypervisor kernel John Allen
2025-08-25 1:46 ` Chao Gao
2025-08-06 20:45 ` [PATCH v3 5/5] KVM: SVM: Enable shadow stack virtualization for SVM John Allen
2025-08-25 1:33 ` Chao Gao
2025-09-03 21:01 ` John Allen
2025-09-05 20:50 ` Chao Gao [this message]
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