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Bae" To: pbonzini@redhat.com, seanjc@google.com Cc: kvm@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, zhao1.liu@intel.com, chang.seok.bae@intel.com Subject: [PATCH v8 15/20] KVM: x86: Guard valid XCR0.APX settings Date: Wed, 30 Sep 2026 21:07:45 +0000 Message-ID: <20260930210750.1487547-16-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260930210750.1487547-1-chang.seok.bae@intel.com> References: <20260930210750.1487547-1-chang.seok.bae@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Prevent invalid XCR0.APX configurations in two cases: conflict with MPX and lack of SVM support. In the non-compacted XSAVE format, APX and MPX conflict on the same offset. Although MPX is being deprecated in practice, KVM should explicitly reject such configurations that set both bits. At this point, only VMX supports EGPRs. SVM will require corresponding extensions to handle EGPR indices. Updating the supported XCR0 mask will be done separately. Suggested-by: Paolo Bonzini Signed-off-by: Chang S. Bae Link: https://lore.kernel.org/ab3f4937-38f5-4354-8850-bf773c159bbe@redhat.com --- arch/x86/kvm/svm/svm.c | 7 ++++++- arch/x86/kvm/x86.c | 4 ++++ 2 files changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 7d59d301e1e5..2962501c4b67 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -5616,8 +5616,13 @@ static __init int svm_hardware_setup(void) return -EOPNOTSUPP; } + /* + * APX introduces EGPRs, which require additional VMCB support. + * Disable APX until the necessary extensions are handled. + */ kvm_caps.supported_xcr0 &= ~(XFEATURE_MASK_BNDREGS | - XFEATURE_MASK_BNDCSR); + XFEATURE_MASK_BNDCSR | + XFEATURE_MASK_APX); if (tsc_scaling) { if (!boot_cpu_has(X86_FEATURE_TSCRATEMSR)) { diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 91666b868ab9..76f70d2631f6 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -699,6 +699,10 @@ int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr) (!(xcr0 & XFEATURE_MASK_BNDCSR))) return 1; + /* MPX and APX conflict in the non-compacted XSAVE format */ + if (xcr0 & XFEATURE_MASK_BNDREGS && xcr0 & XFEATURE_MASK_APX) + return 1; + if (xcr0 & XFEATURE_MASK_AVX512) { if (!(xcr0 & XFEATURE_MASK_YMM)) return 1; -- 2.53.0