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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id f65sm7124998wmf.2.2019.12.19.11.09.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Dec 2019 11:09:58 -0800 (PST) From: Vitaly Kuznetsov To: John Allen , kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, pbonzini@redhat.com, rkrcmar@redhat.com, John Allen Subject: Re: [PATCH] kvm/svm: PKU not currently supported In-Reply-To: <20191219152332.28857-1-john.allen@amd.com> References: <20191219152332.28857-1-john.allen@amd.com> Date: Thu, 19 Dec 2019 20:09:57 +0100 Message-ID: <87immc873u.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org John Allen writes: > Current SVM implementation does not have support for handling PKU. Guests > running on a host with future AMD cpus that support the feature will read > garbage from the PKRU register and will hit segmentation faults on boot as > memory is getting marked as protected that should not be. Ensure that cpuid > from SVM does not advertise the feature. > > Signed-off-by: John Allen > --- > arch/x86/kvm/svm.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c > index 122d4ce3b1ab..f911aa1b41c8 100644 > --- a/arch/x86/kvm/svm.c > +++ b/arch/x86/kvm/svm.c > @@ -5933,6 +5933,8 @@ static void svm_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *entry) > if (avic) > entry->ecx &= ~bit(X86_FEATURE_X2APIC); > break; > + case 0x7: > + entry->ecx &= ~bit(X86_FEATURE_PKU); Would it make more sense to introduce kvm_x86_ops->pku_supported() (and return false for SVM and boot_cpu_has(X86_FEATURE_PKU) for vmx) so we don't set the bit in the first place? > case 0x80000001: > if (nested) > entry->ecx |= (1 << 2); /* Set SVM bit */ -- Vitaly