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([2001:b07:6468:f312:63a7:c72e:ea0e:6045]) by smtp.googlemail.com with ESMTPSA id vk5-20020a170907cbc500b00a1ce56f7b16sm8240761ejc.71.2023.12.13.10.45.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 13 Dec 2023 10:45:42 -0800 (PST) Message-ID: Date: Wed, 13 Dec 2023 19:45:39 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v10 23/50] KVM: SEV: Make AVIC backing, VMSA and VMCB memory allocation SNP safe To: Michael Roth , kvm@vger.kernel.org Cc: 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, seanjc@google.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, marcorr@google.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, zhi.a.wang@intel.com, Brijesh Singh References: <20231016132819.1002933-1-michael.roth@amd.com> <20231016132819.1002933-24-michael.roth@amd.com> From: Paolo Bonzini Autocrypt: addr=pbonzini@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 3F5CD100014 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: ccf4zadnwmbt9bfck1wydiobh93j7h38 X-HE-Tag: 1702493147-635071 X-HE-Meta: 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 Vurmsv3r LO+RH4dhkL73jMfgAJPXJbTUSaWA2OLF5oDVcqDFmLXWBWlw2j5IfCf0VyNh87pUzCMB42gj5sEareTOlyDsYZyZbJC6gMvIGjeid87cPj5wdIoqrz6dOMwkcSiRK+GuVWqYiDrN2kHP+lhFFy3srieMb2yBemUkJDix+GPGbEoEOD17acxeeIj61h5VNBnSxcU28RglGeUW0Za4txe35NMZOKAfcwurkkn61vsANga3nifdglxxQYkYc9cOxGOgnr7rYuXyJx8EwwSHcT/HrjE8g1JM+cDwuXdRzNwhdFfFrPxJBwyskSH4p7ZAxdu7avuqbUzkh0UWpzmxhYT+WSd3mFdkjFaInEcS/fz0k09XPHYY+qhkik7WP9U+pthuF51sgtxXkJBMtBffewG/cCHjzhkqLabAh7sGEV66xy89g7IWLgNc9bhEHCQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 10/16/23 15:27, Michael Roth wrote: > From: Brijesh Singh > > Implement a workaround for an SNP erratum where the CPU will incorrectly > signal an RMP violation #PF if a hugepage (2mb or 1gb) collides with the > RMP entry of a VMCB, VMSA or AVIC backing page. > > When SEV-SNP is globally enabled, the CPU marks the VMCB, VMSA, and AVIC > backing pages as "in-use" via a reserved bit in the corresponding RMP > entry after a successful VMRUN. This is done for _all_ VMs, not just > SNP-Active VMs. > > If the hypervisor accesses an in-use page through a writable > translation, the CPU will throw an RMP violation #PF. On early SNP > hardware, if an in-use page is 2mb aligned and software accesses any > part of the associated 2mb region with a hupage, the CPU will > incorrectly treat the entire 2mb region as in-use and signal a spurious > RMP violation #PF. > > The recommended is to not use the hugepage for the VMCB, VMSA or > AVIC backing page for similar reasons. Add a generic allocator that will > ensure that the page returns is not hugepage (2mb or 1gb) and is safe to > be used when SEV-SNP is enabled. Also implement similar handling for the > VMCB/VMSA pages of nested guests. > > Co-developed-by: Marc Orr > Signed-off-by: Marc Orr > Reported-by: Alper Gun # for nested VMSA case > Co-developed-by: Ashish Kalra > Signed-off-by: Ashish Kalra > Signed-off-by: Brijesh Singh > [mdr: squash in nested guest handling from Ashish] > Signed-off-by: Michael Roth Based on the discussion with Borislav, please move this earlier in the series, before patch 6. Paolo > --- > arch/x86/include/asm/kvm-x86-ops.h | 1 + > arch/x86/include/asm/kvm_host.h | 1 + > arch/x86/kvm/lapic.c | 5 ++++- > arch/x86/kvm/svm/nested.c | 2 +- > arch/x86/kvm/svm/sev.c | 33 ++++++++++++++++++++++++++++++ > arch/x86/kvm/svm/svm.c | 17 ++++++++++++--- > arch/x86/kvm/svm/svm.h | 1 + > 7 files changed, 55 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h > index f1505a5fa781..4ef2eca14287 100644 > --- a/arch/x86/include/asm/kvm-x86-ops.h > +++ b/arch/x86/include/asm/kvm-x86-ops.h > @@ -136,6 +136,7 @@ KVM_X86_OP(vcpu_deliver_sipi_vector) > KVM_X86_OP_OPTIONAL_RET0(vcpu_get_apicv_inhibit_reasons); > KVM_X86_OP_OPTIONAL_RET0(gmem_prepare) > KVM_X86_OP_OPTIONAL(gmem_invalidate) > +KVM_X86_OP_OPTIONAL(alloc_apic_backing_page) > > #undef KVM_X86_OP > #undef KVM_X86_OP_OPTIONAL > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index fa401cb1a552..a3983271ea28 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -1763,6 +1763,7 @@ struct kvm_x86_ops { > > int (*gmem_prepare)(struct kvm *kvm, kvm_pfn_t pfn, gfn_t gfn, int max_order); > void (*gmem_invalidate)(kvm_pfn_t start, kvm_pfn_t end); > + void *(*alloc_apic_backing_page)(struct kvm_vcpu *vcpu); > }; > > struct kvm_x86_nested_ops { > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index dcd60b39e794..631a554c0f48 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -2810,7 +2810,10 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu, int timer_advance_ns) > > vcpu->arch.apic = apic; > > - apic->regs = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT); > + if (kvm_x86_ops.alloc_apic_backing_page) > + apic->regs = static_call(kvm_x86_alloc_apic_backing_page)(vcpu); > + else > + apic->regs = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT); > if (!apic->regs) { > printk(KERN_ERR "malloc apic regs error for vcpu %x\n", > vcpu->vcpu_id); > diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c > index dd496c9e5f91..1f9a3f9eb985 100644 > --- a/arch/x86/kvm/svm/nested.c > +++ b/arch/x86/kvm/svm/nested.c > @@ -1194,7 +1194,7 @@ int svm_allocate_nested(struct vcpu_svm *svm) > if (svm->nested.initialized) > return 0; > > - vmcb02_page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO); > + vmcb02_page = snp_safe_alloc_page(&svm->vcpu); > if (!vmcb02_page) > return -ENOMEM; > svm->nested.vmcb02.ptr = page_address(vmcb02_page); > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > index 088b32657f46..1cfb9232fc74 100644 > --- a/arch/x86/kvm/svm/sev.c > +++ b/arch/x86/kvm/svm/sev.c > @@ -3211,3 +3211,36 @@ void sev_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector) > break; > } > } > + > +struct page *snp_safe_alloc_page(struct kvm_vcpu *vcpu) > +{ > + unsigned long pfn; > + struct page *p; > + > + if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP)) > + return alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO); > + > + /* > + * Allocate an SNP safe page to workaround the SNP erratum where > + * the CPU will incorrectly signal an RMP violation #PF if a > + * hugepage (2mb or 1gb) collides with the RMP entry of VMCB, VMSA > + * or AVIC backing page. The recommeded workaround is to not use the > + * hugepage. > + * > + * Allocate one extra page, use a page which is not 2mb aligned > + * and free the other. > + */ > + p = alloc_pages(GFP_KERNEL_ACCOUNT | __GFP_ZERO, 1); > + if (!p) > + return NULL; > + > + split_page(p, 1); > + > + pfn = page_to_pfn(p); > + if (IS_ALIGNED(pfn, PTRS_PER_PMD)) > + __free_page(p++); > + else > + __free_page(p + 1); > + > + return p; > +} > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index 1e7fb1ea45f7..8e4ef0cd968a 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -706,7 +706,7 @@ static int svm_cpu_init(int cpu) > int ret = -ENOMEM; > > memset(sd, 0, sizeof(struct svm_cpu_data)); > - sd->save_area = alloc_page(GFP_KERNEL | __GFP_ZERO); > + sd->save_area = snp_safe_alloc_page(NULL); > if (!sd->save_area) > return ret; > > @@ -1425,7 +1425,7 @@ static int svm_vcpu_create(struct kvm_vcpu *vcpu) > svm = to_svm(vcpu); > > err = -ENOMEM; > - vmcb01_page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO); > + vmcb01_page = snp_safe_alloc_page(vcpu); > if (!vmcb01_page) > goto out; > > @@ -1434,7 +1434,7 @@ static int svm_vcpu_create(struct kvm_vcpu *vcpu) > * SEV-ES guests require a separate VMSA page used to contain > * the encrypted register state of the guest. > */ > - vmsa_page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO); > + vmsa_page = snp_safe_alloc_page(vcpu); > if (!vmsa_page) > goto error_free_vmcb_page; > > @@ -4876,6 +4876,16 @@ static int svm_vm_init(struct kvm *kvm) > return 0; > } > > +static void *svm_alloc_apic_backing_page(struct kvm_vcpu *vcpu) > +{ > + struct page *page = snp_safe_alloc_page(vcpu); > + > + if (!page) > + return NULL; > + > + return page_address(page); > +} > + > static struct kvm_x86_ops svm_x86_ops __initdata = { > .name = KBUILD_MODNAME, > > @@ -5007,6 +5017,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = { > > .vcpu_deliver_sipi_vector = svm_vcpu_deliver_sipi_vector, > .vcpu_get_apicv_inhibit_reasons = avic_vcpu_get_apicv_inhibit_reasons, > + .alloc_apic_backing_page = svm_alloc_apic_backing_page, > }; > > /* > diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h > index c13070d00910..b7b8bf73cbb9 100644 > --- a/arch/x86/kvm/svm/svm.h > +++ b/arch/x86/kvm/svm/svm.h > @@ -694,6 +694,7 @@ void sev_es_vcpu_reset(struct vcpu_svm *svm); > void sev_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector); > void sev_es_prepare_switch_to_guest(struct sev_es_save_area *hostsa); > void sev_es_unmap_ghcb(struct vcpu_svm *svm); > +struct page *snp_safe_alloc_page(struct kvm_vcpu *vcpu); > > /* vmenter.S */ >