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([2001:b07:6468:f312:5e2c:eb9a:a8b6:fd3e]) by smtp.googlemail.com with ESMTPSA id b13-20020a05600c4e0d00b003816cb4892csm12523764wmq.0.2022.03.02.12.39.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 02 Mar 2022 12:39:07 -0800 (PST) Message-ID: <217cc048-8ca7-2b7b-141f-f44f0d95eec5@redhat.com> Date: Wed, 2 Mar 2022 21:39:04 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH v2 4/7] KVM: x86/mmu: Zap only obsolete roots if a root shadow page is zapped Content-Language: en-US To: Sean Christopherson Cc: Christian Borntraeger , Janosch Frank , David Hildenbrand , Claudio Imbrenda , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Ben Gardon , Lai Jiangshan References: <20220225182248.3812651-1-seanjc@google.com> <20220225182248.3812651-5-seanjc@google.com> <40a22c39-9da4-6c37-8ad0-b33970e35a2b@redhat.com> From: Paolo Bonzini In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/2/22 20:45, Sean Christopherson wrote: > AMD NPT is hosed because KVM's awful ASID scheme doesn't assign an ASID per root > and doesn't force a new ASID. IMO, this is an SVM mess and not a TDP MMU bug. I agree. > In the short term, I think something like the following would suffice. Long term, > we really need to redo SVM ASID management so that ASIDs are tied to a KVM root. diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index c5e3f219803e..7899ca4748c7 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -3857,6 +3857,9 @@ static void svm_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa, unsigned long cr3; if (npt_enabled) { + if (is_tdp_mmu_root(root_hpa)) + svm->current_vmcb->asid_generation = 0; + svm->vmcb->control.nested_cr3 = __sme_set(root_hpa); vmcb_mark_dirty(svm->vmcb, VMCB_NPT); Why not just new_asid (even unconditionally, who cares)? BTW yeah, the smoke test worked but the actual one failed horribly. Paolo