| Message ID | 20210820155918.7518-28-brijesh.singh@amd.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Herbert Xu |
| Headers | show |
| Series | Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support | expand |
> @@ -2364,16 +2467,29 @@ static void sev_flush_guest_memory(struct vcpu_svm *svm, void *va, > void sev_free_vcpu(struct kvm_vcpu *vcpu) > { > struct vcpu_svm *svm; > + u64 pfn; > > if (!sev_es_guest(vcpu->kvm)) > return; > > svm = to_svm(vcpu); > + pfn = __pa(svm->vmsa) >> PAGE_SHIFT; > > if (vcpu->arch.guest_state_protected) > sev_flush_guest_memory(svm, svm->vmsa, PAGE_SIZE); > + > + /* > + * If its an SNP guest, then VMSA was added in the RMP entry as > + * a guest owned page. Transition the page to hyperivosr state > + * before releasing it back to the system. > + */ > + if (sev_snp_guest(vcpu->kvm) && > + host_rmp_make_shared(pfn, PG_LEVEL_4K, false)) > + goto skip_vmsa_free; > + > __free_page(virt_to_page(svm->vmsa)); > > +skip_vmsa_free: > if (svm->ghcb_sa_free) > kfree(svm->ghcb_sa); > } Hi Ashish. We're still working with this patch set internally. We found a bug that I wanted to report in this patch. Above, we need to flush the VMSA page, `svm->vmsa`, _after_ we call `host_rmp_make_shared()` to mark the page is shared. Otherwise, the host gets an RMP violation when it tries to flush the guest-owned VMSA page. The bug was silent, at least on our Milan platforms, bef reo d45829b351ee6 ("KVM: SVM: Flush when freeing encrypted pages even on SME_COHERENT CPUs"), because the `sev_flush_guest_memory()` helper was a noop on platforms with the SME_COHERENT feature. However, after d45829b351ee6, we unconditionally do the flush to keep the IO address space coherent. And then we hit this bug. Thanks, Marc
[AMD Official Use Only - General] Hello Marc, -----Original Message----- From: Marc Orr <marcorr@google.com> Sent: Wednesday, May 18, 2022 3:21 PM To: Kalra, Ashish <Ashish.Kalra@amd.com> Cc: x86 <x86@kernel.org>; LKML <linux-kernel@vger.kernel.org>; kvm list <kvm@vger.kernel.org>; linux-coco@lists.linux.dev; linux-mm@kvack.org; Linux Crypto Mailing List <linux-crypto@vger.kernel.org>; Thomas Gleixner <tglx@linutronix.de>; Ingo Molnar <mingo@redhat.com>; Joerg Roedel <jroedel@suse.de>; Lendacky, Thomas <Thomas.Lendacky@amd.com>; H. Peter Anvin <hpa@zytor.com>; Ard Biesheuvel <ardb@kernel.org>; Paolo Bonzini <pbonzini@redhat.com>; Sean Christopherson <seanjc@google.com>; Vitaly Kuznetsov <vkuznets@redhat.com>; Wanpeng Li <wanpengli@tencent.com>; Jim Mattson <jmattson@google.com>; Andy Lutomirski <luto@kernel.org>; Dave Hansen <dave.hansen@linux.intel.com>; Sergio Lopez <slp@redhat.com>; Peter Gonda <pgonda@google.com>; Peter Zijlstra <peterz@infradead.org>; Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>; David Rientjes <rientjes@google.com>; Dov Murik <dovmurik@linux.ibm.com>; Tobin Feldman-Fitzthum <tobin@ibm.com>; Borislav Petkov <bp@alien8.de>; Roth, Michael <Michael.Roth@amd.com>; Vlastimil Babka <vbabka@suse.cz>; Kirill A . Shutemov <kirill@shutemov.name>; Andi Kleen <ak@linux.intel.com>; Tony Luck <tony.luck@intel.com>; Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@linux.intel.com>; Alper Gun <alpergun@google.com> Subject: Re: [PATCH Part2 v5 27/45] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_FINISH command > @@ -2364,16 +2467,29 @@ static void sev_flush_guest_memory(struct > vcpu_svm *svm, void *va, void sev_free_vcpu(struct kvm_vcpu *vcpu) { > struct vcpu_svm *svm; > + u64 pfn; > > if (!sev_es_guest(vcpu->kvm)) > return; > > svm = to_svm(vcpu); > + pfn = __pa(svm->vmsa) >> PAGE_SHIFT; > > if (vcpu->arch.guest_state_protected) > sev_flush_guest_memory(svm, svm->vmsa, PAGE_SIZE); > + > + /* > + * If its an SNP guest, then VMSA was added in the RMP entry as > + * a guest owned page. Transition the page to hyperivosr state > + * before releasing it back to the system. > + */ > + if (sev_snp_guest(vcpu->kvm) && > + host_rmp_make_shared(pfn, PG_LEVEL_4K, false)) > + goto skip_vmsa_free; > + > __free_page(virt_to_page(svm->vmsa)); > > +skip_vmsa_free: > if (svm->ghcb_sa_free) > kfree(svm->ghcb_sa); > } >Hi Ashish. We're still working with this patch set internally. We found a bug that I wanted to report in this patch. Above, we need to flush the VMSA page, `svm->vmsa`, _after_ we call `host_rmp_make_shared()` to mark the page is shared. >Otherwise, the host gets an RMP violation when it tries to flush the guest-owned VMSA page. >The bug was silent, at least on our Milan platforms, bef reo >d45829b351ee6 ("KVM: SVM: Flush when freeing encrypted pages even on SME_COHERENT CPUs"), because the `sev_flush_guest_memory()` helper was a noop on platforms with the SME_COHERENT feature. However, after d45829b351ee6, we >unconditionally do the flush to keep the IO address space coherent. And then we hit this bug. Yes I have already hit this bug and added a fix as below: commit 944fba38cbd3baf1ece76197630bd45e83089f14 Author: Ashish Kalra <ashish.kalra@amd.com> Date: Tue May 3 14:33:29 2022 +0000 KVM: SVM: Fix VMSA flush for an SNP guest. If its an SNP guest, then VMSA was added in the RMP entry as a guest owned page and also removed from the kernel direct map so flush it later after it is transitioned back to hypervisor state and restored in the direct map. Signed-off-by: Ashish Kalra <ashish.kalra@amd.com> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index cc7c34d8b0db..0f772a0f1d35 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -2840,27 +2840,23 @@ void sev_free_vcpu(struct kvm_vcpu *vcpu) svm = to_svm(vcpu); - if (vcpu->arch.guest_state_protected) - sev_flush_encrypted_page(vcpu, svm->sev_es.vmsa); - /* * If its an SNP guest, then VMSA was added in the RMP entry as * a guest owned page. Transition the page to hyperivosr state * before releasing it back to the system. + * Also the page is removed from the kernel direct map, so flush it + * later after it is transitioned back to hypervisor state and + * restored in the direct map. */ if (sev_snp_guest(vcpu->kvm)) { u64 pfn = __pa(svm->sev_es.vmsa) >> PAGE_SHIFT; if (host_rmp_make_shared(pfn, PG_LEVEL_4K, false)) goto skip_vmsa_free; } + if (vcpu->arch.guest_state_protected) + sev_flush_encrypted_page(vcpu, svm->sev_es.vmsa); + __free_page(virt_to_page(svm->sev_es.vmsa)); skip_vmsa_free: This will be part of the next hypervisor patches which we will be posting next. Thanks, Ashish
diff --git a/Documentation/virt/kvm/amd-memory-encryption.rst b/Documentation/virt/kvm/amd-memory-encryption.rst index ddcd94e9ffed..c7332e0e0baa 100644 --- a/Documentation/virt/kvm/amd-memory-encryption.rst +++ b/Documentation/virt/kvm/amd-memory-encryption.rst @@ -506,6 +506,28 @@ Returns: 0 on success, -negative on error See the SEV-SNP spec for further details on how to build the VMPL permission mask and page type. +21. KVM_SNP_LAUNCH_FINISH +------------------------- + +After completion of the SNP guest launch flow, the KVM_SNP_LAUNCH_FINISH command can be +issued to make the guest ready for the execution. + +Parameters (in): struct kvm_sev_snp_launch_finish + +Returns: 0 on success, -negative on error + +:: + + struct kvm_sev_snp_launch_finish { + __u64 id_block_uaddr; + __u64 id_auth_uaddr; + __u8 id_block_en; + __u8 auth_key_en; + __u8 host_data[32]; + }; + + +See SEV-SNP specification for further details on launch finish input parameters. References ========== diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index dcef0ae5f8e4..248096a5c307 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -1813,6 +1813,106 @@ static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp) return ret; } +static int snp_launch_update_vmsa(struct kvm *kvm, struct kvm_sev_cmd *argp) +{ + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; + struct sev_data_snp_launch_update data = {}; + int i, ret; + + data.gctx_paddr = __psp_pa(sev->snp_context); + data.page_type = SNP_PAGE_TYPE_VMSA; + + for (i = 0; i < kvm->created_vcpus; i++) { + struct vcpu_svm *svm = to_svm(kvm->vcpus[i]); + u64 pfn = __pa(svm->vmsa) >> PAGE_SHIFT; + + /* Perform some pre-encryption checks against the VMSA */ + ret = sev_es_sync_vmsa(svm); + if (ret) + return ret; + + /* Transition the VMSA page to a firmware state. */ + ret = rmp_make_private(pfn, -1, PG_LEVEL_4K, sev->asid, true); + if (ret) + return ret; + + /* Issue the SNP command to encrypt the VMSA */ + data.address = __sme_pa(svm->vmsa); + ret = __sev_issue_cmd(argp->sev_fd, SEV_CMD_SNP_LAUNCH_UPDATE, + &data, &argp->error); + if (ret) { + snp_page_reclaim(pfn); + return ret; + } + + svm->vcpu.arch.guest_state_protected = true; + } + + return 0; +} + +static int snp_launch_finish(struct kvm *kvm, struct kvm_sev_cmd *argp) +{ + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; + struct sev_data_snp_launch_finish *data; + void *id_block = NULL, *id_auth = NULL; + struct kvm_sev_snp_launch_finish params; + int ret; + + if (!sev_snp_guest(kvm)) + return -ENOTTY; + + if (!sev->snp_context) + return -EINVAL; + + if (copy_from_user(¶ms, (void __user *)(uintptr_t)argp->data, sizeof(params))) + return -EFAULT; + + /* Measure all vCPUs using LAUNCH_UPDATE before we finalize the launch flow. */ + ret = snp_launch_update_vmsa(kvm, argp); + if (ret) + return ret; + + data = kzalloc(sizeof(*data), GFP_KERNEL_ACCOUNT); + if (!data) + return -ENOMEM; + + if (params.id_block_en) { + id_block = psp_copy_user_blob(params.id_block_uaddr, KVM_SEV_SNP_ID_BLOCK_SIZE); + if (IS_ERR(id_block)) { + ret = PTR_ERR(id_block); + goto e_free; + } + + data->id_block_en = 1; + data->id_block_paddr = __sme_pa(id_block); + } + + if (params.auth_key_en) { + id_auth = psp_copy_user_blob(params.id_auth_uaddr, KVM_SEV_SNP_ID_AUTH_SIZE); + if (IS_ERR(id_auth)) { + ret = PTR_ERR(id_auth); + goto e_free_id_block; + } + + data->auth_key_en = 1; + data->id_auth_paddr = __sme_pa(id_auth); + } + + data->gctx_paddr = __psp_pa(sev->snp_context); + ret = sev_issue_cmd(kvm, SEV_CMD_SNP_LAUNCH_FINISH, data, &argp->error); + + kfree(id_auth); + +e_free_id_block: + kfree(id_block); + +e_free: + kfree(data); + + return ret; +} + int svm_mem_enc_op(struct kvm *kvm, void __user *argp) { struct kvm_sev_cmd sev_cmd; @@ -1908,6 +2008,9 @@ int svm_mem_enc_op(struct kvm *kvm, void __user *argp) case KVM_SEV_SNP_LAUNCH_UPDATE: r = snp_launch_update(kvm, &sev_cmd); break; + case KVM_SEV_SNP_LAUNCH_FINISH: + r = snp_launch_finish(kvm, &sev_cmd); + break; default: r = -EINVAL; goto out; @@ -2364,16 +2467,29 @@ static void sev_flush_guest_memory(struct vcpu_svm *svm, void *va, void sev_free_vcpu(struct kvm_vcpu *vcpu) { struct vcpu_svm *svm; + u64 pfn; if (!sev_es_guest(vcpu->kvm)) return; svm = to_svm(vcpu); + pfn = __pa(svm->vmsa) >> PAGE_SHIFT; if (vcpu->arch.guest_state_protected) sev_flush_guest_memory(svm, svm->vmsa, PAGE_SIZE); + + /* + * If its an SNP guest, then VMSA was added in the RMP entry as + * a guest owned page. Transition the page to hyperivosr state + * before releasing it back to the system. + */ + if (sev_snp_guest(vcpu->kvm) && + host_rmp_make_shared(pfn, PG_LEVEL_4K, false)) + goto skip_vmsa_free; + __free_page(virt_to_page(svm->vmsa)); +skip_vmsa_free: if (svm->ghcb_sa_free) kfree(svm->ghcb_sa); } diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 0681be4bdfdf..ab9b1c82b0ee 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -1716,6 +1716,7 @@ enum sev_cmd_id { KVM_SEV_SNP_INIT, KVM_SEV_SNP_LAUNCH_START, KVM_SEV_SNP_LAUNCH_UPDATE, + KVM_SEV_SNP_LAUNCH_FINISH, KVM_SEV_NR_MAX, }; @@ -1850,6 +1851,19 @@ struct kvm_sev_snp_launch_update { __u8 vmpl1_perms; }; +#define KVM_SEV_SNP_ID_BLOCK_SIZE 96 +#define KVM_SEV_SNP_ID_AUTH_SIZE 4096 +#define KVM_SEV_SNP_FINISH_DATA_SIZE 32 + +struct kvm_sev_snp_launch_finish { + __u64 id_block_uaddr; + __u64 id_auth_uaddr; + __u8 id_block_en; + __u8 auth_key_en; + __u8 host_data[KVM_SEV_SNP_FINISH_DATA_SIZE]; + __u8 pad[6]; +}; + #define KVM_DEV_ASSIGN_ENABLE_IOMMU (1 << 0) #define KVM_DEV_ASSIGN_PCI_2_3 (1 << 1) #define KVM_DEV_ASSIGN_MASK_INTX (1 << 2)
The KVM_SEV_SNP_LAUNCH_FINISH finalize the cryptographic digest and stores it as the measurement of the guest at launch. While finalizing the launch flow, it also issues the LAUNCH_UPDATE command to encrypt the VMSA pages. Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> --- .../virt/kvm/amd-memory-encryption.rst | 22 ++++ arch/x86/kvm/svm/sev.c | 116 ++++++++++++++++++ include/uapi/linux/kvm.h | 14 +++ 3 files changed, 152 insertions(+)