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AJvYcCUXZ44LI8Nc0Phu6UvtWZygW703Rzjn/4TNoUil3x/Dwe0DLqGp5rE6fPZ2gV4Bnt45euIVbeGnYTOpyz3NB6sIj6A= X-Gm-Message-State: AOJu0Ywxj3WQXvtB0oqZpBo0guy5NuUW4Jyu/28VSmPGMpvt/LSvo3xn P7rebcEUBN2PvFTB0K7O7PlgDZCUyRXdafyd695abgZ4Y/iHgfQwMpOnqDp9Xm6DrRQHo3eL2YC AjQ== X-Google-Smtp-Source: AGHT+IF06EpTOwvZeQGKlqPQtXFzYGfZPqUfmBFZuyaYdLAzcsdi+7awfJdAqckqz+IcAQhBBvcZ3k/AgAM= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a05:6902:1205:b0:de5:2325:72ac with SMTP id s5-20020a056902120500b00de5232572acmr1331874ybu.6.1714004238029; Wed, 24 Apr 2024 17:17:18 -0700 (PDT) Date: Wed, 24 Apr 2024 17:17:16 -0700 In-Reply-To: <20240421180122.1650812-18-michael.roth@amd.com> Mime-Version: 1.0 References: <20240421180122.1650812-1-michael.roth@amd.com> <20240421180122.1650812-18-michael.roth@amd.com> Message-ID: Subject: Re: [PATCH v14 17/22] KVM: SEV: Avoid WBINVD for HVA-based MMU notifications for SNP From: Sean Christopherson To: Michael Roth Cc: kvm@vger.kernel.org, linux-coco@lists.linux.dev, linux-mm@kvack.org, linux-crypto@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, jroedel@suse.de, thomas.lendacky@amd.com, hpa@zytor.com, ardb@kernel.org, pbonzini@redhat.com, vkuznets@redhat.com, jmattson@google.com, luto@kernel.org, dave.hansen@linux.intel.com, slp@redhat.com, pgonda@google.com, peterz@infradead.org, srinivas.pandruvada@linux.intel.com, rientjes@google.com, dovmurik@linux.ibm.com, tobin@ibm.com, bp@alien8.de, vbabka@suse.cz, kirill@shutemov.name, ak@linux.intel.com, tony.luck@intel.com, sathyanarayanan.kuppuswamy@linux.intel.com, alpergun@google.com, jarkko@kernel.org, ashish.kalra@amd.com, nikunj.dadhania@amd.com, pankaj.gupta@amd.com, liam.merwick@oracle.com Content-Type: text/plain; charset="us-ascii" X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 1479A18001C X-Stat-Signature: uzdm53n1ni3mbwyp4zoybgn9hksfm5h1 X-HE-Tag: 1714004239-541303 X-HE-Meta: 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 +23vwiwn 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.009165, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, Apr 21, 2024, Michael Roth wrote: > From: Ashish Kalra > > With SNP/guest_memfd, private/encrypted memory should not be mappable, > and MMU notifications for HVA-mapped memory will only be relevant to > unencrypted guest memory. Therefore, the rationale behind issuing a > wbinvd_on_all_cpus() in sev_guest_memory_reclaimed() should not apply > for SNP guests and can be ignored. > > Signed-off-by: Ashish Kalra > Reviewed-by: Paolo Bonzini > [mdr: Add some clarifications in commit] > Signed-off-by: Michael Roth > --- > arch/x86/kvm/svm/sev.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > index 243369e302f4..cf00a811aca5 100644 > --- a/arch/x86/kvm/svm/sev.c > +++ b/arch/x86/kvm/svm/sev.c > @@ -3042,7 +3042,14 @@ static void sev_flush_encrypted_page(struct kvm_vcpu *vcpu, void *va) > > void sev_guest_memory_reclaimed(struct kvm *kvm) > { > - if (!sev_guest(kvm)) > + /* > + * With SNP+gmem, private/encrypted memory should be Not should, *is*. > + * unreachable via the hva-based mmu notifiers. Additionally, > + * for shared->private translations, H/W coherency will ensure > + * first guest access to the page would clear out any existing > + * dirty copies of that cacheline. I don't see how this second part is relevant. > + */ > + if (!sev_guest(kvm) || sev_snp_guest(kvm)) > return; > > wbinvd_on_all_cpus(); > -- > 2.25.1 >