From: Brijesh Singh <brijesh.singh@xxxxxxx> A key aspect of a launching an SNP guest is initializing it with a known/measured payload which is then encrypted into guest memory as pre-validated private pages and then measured into the cryptographic launch context created with KVM_SEV_SNP_LAUNCH_START so that the guest can attest itself after booting. Since all private pages are provided by guest_memfd, make use of the kvm_gmem_populate() interface to handle this. The general flow is that guest_memfd will handle allocating the pages associated with the GPA ranges being initialized by each particular call of KVM_SEV_SNP_LAUNCH_UPDATE, copying data from userspace into those pages, and then the post_populate callback will do the work of setting the RMP entries for these pages to private and issuing the SNP firmware calls to encrypt/measure them. For more information see the SEV-SNP specification. Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx> Co-developed-by: Michael Roth <michael.roth@xxxxxxx> Signed-off-by: Michael Roth <michael.roth@xxxxxxx> Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx> --- .../virt/kvm/x86/amd-memory-encryption.rst | 54 ++++ arch/x86/include/uapi/asm/kvm.h | 19 ++ arch/x86/kvm/svm/sev.c | 237 ++++++++++++++++++ 3 files changed, 310 insertions(+) diff --git a/Documentation/virt/kvm/x86/amd-memory-encryption.rst b/Documentation/virt/kvm/x86/amd-memory-encryption.rst index d4c4a0b90bc9..60728868c5c6 100644 --- a/Documentation/virt/kvm/x86/amd-memory-encryption.rst +++ b/Documentation/virt/kvm/x86/amd-memory-encryption.rst @@ -483,6 +483,60 @@ Returns: 0 on success, -negative on error See SNP_LAUNCH_START in the SEV-SNP specification [snp-fw-abi]_ for further details on the input parameters in ``struct kvm_sev_snp_launch_start``. +19. KVM_SEV_SNP_LAUNCH_UPDATE +----------------------------- + +The KVM_SEV_SNP_LAUNCH_UPDATE command is used for loading userspace-provided +data into a guest GPA range, measuring the contents into the SNP guest context +created by KVM_SEV_SNP_LAUNCH_START, and then encrypting/validating that GPA +range so that it will be immediately readable using the encryption key +associated with the guest context once it is booted, after which point it can +attest the measurement associated with its context before unlocking any +secrets. + +It is required that the GPA ranges initialized by this command have had the +KVM_MEMORY_ATTRIBUTE_PRIVATE attribute set in advance. See the documentation +for KVM_SET_MEMORY_ATTRIBUTES for more details on this aspect. + +Upon success, this command is not guaranteed to have processed the entire +range requested. Instead, the ``gfn_start``, ``uaddr``, and ``len`` fields of +``struct kvm_sev_snp_launch_update`` will be updated to correspond to the +remaining range that has yet to be processed. The caller should continue +calling this command until those fields indicate the entire range has been +processed, e.g. ``len`` is 0, ``gfn_start`` is equal to the last GFN in the +range plus 1, and ``uaddr`` is the last byte of the userspace-provided source +buffer address plus 1. In the case where ``type`` is KVM_SEV_SNP_PAGE_TYPE_ZERO, +``uaddr`` will be ignored completely. + +Parameters (in): struct kvm_sev_snp_launch_update + +Returns: 0 on success, < 0 on error, -EAGAIN if caller should retry + +:: + + struct kvm_sev_snp_launch_update { + __u64 gfn_start; /* Guest page number to load/encrypt data into. */ + __u64 uaddr; /* Userspace address of data to be loaded/encrypted. */ + __u64 len; /* 4k-aligned length in bytes to copy into guest memory.*/ + __u8 type; /* The type of the guest pages being initialized. */ + __u8 pad0; + __u16 flags; /* Must be zero. */ + __u32 pad1; + __u64 pad2[4]; + + }; + +where the allowed values for page_type are #define'd as:: + + KVM_SEV_SNP_PAGE_TYPE_NORMAL + KVM_SEV_SNP_PAGE_TYPE_ZERO + KVM_SEV_SNP_PAGE_TYPE_UNMEASURED + KVM_SEV_SNP_PAGE_TYPE_SECRETS + KVM_SEV_SNP_PAGE_TYPE_CPUID + +See the SEV-SNP spec [snp-fw-abi]_ for further details on how each page type is +used/measured. + Device attribute API ==================== diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h index 5765391f0fdb..3c9255de76db 100644 --- a/arch/x86/include/uapi/asm/kvm.h +++ b/arch/x86/include/uapi/asm/kvm.h @@ -699,6 +699,7 @@ enum sev_cmd_id { /* SNP-specific commands */ KVM_SEV_SNP_LAUNCH_START = 100, + KVM_SEV_SNP_LAUNCH_UPDATE, KVM_SEV_NR_MAX, }; @@ -833,6 +834,24 @@ struct kvm_sev_snp_launch_start { __u64 pad1[4]; }; +/* Kept in sync with firmware values for simplicity. */ +#define KVM_SEV_SNP_PAGE_TYPE_NORMAL 0x1 +#define KVM_SEV_SNP_PAGE_TYPE_ZERO 0x3 +#define KVM_SEV_SNP_PAGE_TYPE_UNMEASURED 0x4 +#define KVM_SEV_SNP_PAGE_TYPE_SECRETS 0x5 +#define KVM_SEV_SNP_PAGE_TYPE_CPUID 0x6 + +struct kvm_sev_snp_launch_update { + __u64 gfn_start; + __u64 uaddr; + __u64 len; + __u8 type; + __u8 pad0; + __u16 flags; + __u32 pad1; + __u64 pad2[4]; +}; + #define KVM_X2APIC_API_USE_32BIT_IDS (1ULL << 0) #define KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK (1ULL << 1) diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 9d08d1202544..d3ae4ded91df 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -258,6 +258,35 @@ static void sev_decommission(unsigned int handle) sev_guest_decommission(&decommission, NULL); } +static int snp_page_reclaim(u64 pfn) +{ + struct sev_data_snp_page_reclaim data = {0}; + int err, rc; + + data.paddr = __sme_set(pfn << PAGE_SHIFT); + rc = sev_do_cmd(SEV_CMD_SNP_PAGE_RECLAIM, &data, &err); + if (WARN_ON_ONCE(rc)) { + /* + * This shouldn't happen under normal circumstances, but if the + * reclaim failed, then the page is no longer safe to use. + */ + snp_leak_pages(pfn, 1); + } + + return rc; +} + +static int host_rmp_make_shared(u64 pfn, enum pg_level level) +{ + int rc; + + rc = rmp_make_shared(pfn, level); + if (rc) + snp_leak_pages(pfn, page_level_size(level) >> PAGE_SHIFT); + + return rc; +} + static void sev_unbind_asid(struct kvm *kvm, unsigned int handle) { struct sev_data_deactivate deactivate; @@ -2118,6 +2147,211 @@ static int snp_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp) return rc; } +struct sev_gmem_populate_args { + __u8 type; + int sev_fd; + int fw_error; +}; + +static int sev_gmem_post_populate(struct kvm *kvm, gfn_t gfn_start, kvm_pfn_t pfn, + void __user *src, int order, void *opaque) +{ + struct sev_gmem_populate_args *sev_populate_args = opaque; + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; + int n_private = 0, ret, i; + int npages = (1 << order); + gfn_t gfn; + + pr_debug("%s: gfn_start 0x%llx pfn_start 0x%llx npages %d\n", + __func__, gfn_start, pfn, npages); + + if (WARN_ON_ONCE(sev_populate_args->type != KVM_SEV_SNP_PAGE_TYPE_ZERO && !src)) { + ret = -EINVAL; + goto out; + } + + for (gfn = gfn_start, i = 0; gfn < gfn_start + npages; gfn++, i++) { + struct sev_data_snp_launch_update fw_args = {0}; + bool assigned; + void *vaddr; + int level; + + if (!kvm_mem_is_private(kvm, gfn)) { + pr_debug("%s: Failed to ensure GFN 0x%llx has private memory attribute set\n", + __func__, gfn); + ret = -EINVAL; + break; + } + + ret = snp_lookup_rmpentry((u64)pfn + i, &assigned, &level); + if (ret || assigned) { + pr_debug("%s: Failed to ensure GFN 0x%llx RMP entry is initial shared state, ret: %d assigned: %d\n", + __func__, gfn, ret, assigned); + ret = -EINVAL; + break; + } + + if (src) { + vaddr = kmap_local_pfn(pfn + i); + ret = copy_from_user(vaddr, src + i * PAGE_SIZE, PAGE_SIZE); + if (ret) { + pr_debug("Failed to copy source page into GFN 0x%llx\n", gfn); + goto out_unmap; + } + } + + ret = rmp_make_private(pfn + i, gfn << PAGE_SHIFT, PG_LEVEL_4K, + sev_get_asid(kvm), true); + if (ret) { + pr_debug("%s: Failed to mark RMP entry for GFN 0x%llx as private, ret: %d\n", + __func__, gfn, ret); + goto out_unmap; + } + + n_private++; + + fw_args.gctx_paddr = __psp_pa(sev->snp_context); + fw_args.address = __sme_set(pfn_to_hpa(pfn + i)); + fw_args.page_size = PG_LEVEL_TO_RMP(PG_LEVEL_4K); + fw_args.page_type = sev_populate_args->type; + ret = __sev_issue_cmd(sev_populate_args->sev_fd, SEV_CMD_SNP_LAUNCH_UPDATE, + &fw_args, &sev_populate_args->fw_error); + if (ret) { + pr_debug("%s: SEV-SNP launch update failed, ret: 0x%x, fw_error: 0x%x\n", + __func__, ret, sev_populate_args->fw_error); + + if (WARN_ON_ONCE(snp_page_reclaim(pfn + i))) + goto out_unmap; + + /* + * When invalid CPUID function entries are detected, + * firmware writes the expected values into the page and + * leaves it unencrypted so it can be used for debugging + * and error-reporting. + * + * Copy this page back into the source buffer so + * userspace can use this information to provide + * information on which CPUID leaves/fields failed CPUID + * validation. + */ + if (sev_populate_args->type == KVM_SEV_SNP_PAGE_TYPE_CPUID && + sev_populate_args->fw_error == SEV_RET_INVALID_PARAM) { + if (WARN_ON_ONCE(host_rmp_make_shared(pfn + i, PG_LEVEL_4K))) + goto out_unmap; + + if (copy_to_user(src + i * PAGE_SIZE, vaddr, + PAGE_SIZE)) + pr_debug("Failed to write CPUID page back to userspace\n"); + + /* PFN is hypervisor-owned at this point, skip cleanup for it. */ + n_private--; + } + } + +out_unmap: + kunmap_local(vaddr); + if (ret) + break; + } + +out: + if (ret) { + pr_debug("%s: exiting with error ret %d, restoring %d gmem PFNs to shared.\n", + __func__, ret, n_private); + for (i = 0; i < n_private; i++) + WARN_ON_ONCE(host_rmp_make_shared(pfn + i, PG_LEVEL_4K)); + } + + return ret; +} + +static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp) +{ + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; + struct sev_gmem_populate_args sev_populate_args = {0}; + struct kvm_sev_snp_launch_update params; + struct kvm_memory_slot *memslot; + long npages, count; + void __user *src; + int ret = 0; + + if (!sev_snp_guest(kvm) || !sev->snp_context) + return -EINVAL; + + if (copy_from_user(¶ms, u64_to_user_ptr(argp->data), sizeof(params))) + return -EFAULT; + + pr_debug("%s: GFN start 0x%llx length 0x%llx type %d flags %d\n", __func__, + params.gfn_start, params.len, params.type, params.flags); + + if (!PAGE_ALIGNED(params.len) || params.flags || + (params.type != KVM_SEV_SNP_PAGE_TYPE_NORMAL && + params.type != KVM_SEV_SNP_PAGE_TYPE_ZERO && + params.type != KVM_SEV_SNP_PAGE_TYPE_UNMEASURED && + params.type != KVM_SEV_SNP_PAGE_TYPE_SECRETS && + params.type != KVM_SEV_SNP_PAGE_TYPE_CPUID)) + return -EINVAL; + + npages = params.len / PAGE_SIZE; + + /* + * For each GFN that's being prepared as part of the initial guest + * state, the following pre-conditions are verified: + * + * 1) The backing memslot is a valid private memslot. + * 2) The GFN has been set to private via KVM_SET_MEMORY_ATTRIBUTES + * beforehand. + * 3) The PFN of the guest_memfd has not already been set to private + * in the RMP table. + * + * The KVM MMU relies on kvm->mmu_invalidate_seq to retry nested page + * faults if there's a race between a fault and an attribute update via + * KVM_SET_MEMORY_ATTRIBUTES, and a similar approach could be utilized + * here. However, kvm->slots_lock guards against both this as well as + * concurrent memslot updates occurring while these checks are being + * performed, so use that here to make it easier to reason about the + * initial expected state and better guard against unexpected + * situations. + */ + mutex_lock(&kvm->slots_lock); + + memslot = gfn_to_memslot(kvm, params.gfn_start); + if (!kvm_slot_can_be_private(memslot)) { + ret = -EINVAL; + goto out; + } + + sev_populate_args.sev_fd = argp->sev_fd; + sev_populate_args.type = params.type; + src = params.type == KVM_SEV_SNP_PAGE_TYPE_ZERO ? NULL : u64_to_user_ptr(params.uaddr); + + count = kvm_gmem_populate(kvm, params.gfn_start, src, npages, + sev_gmem_post_populate, &sev_populate_args); + if (count < 0) { + argp->error = sev_populate_args.fw_error; + pr_debug("%s: kvm_gmem_populate failed, ret %ld (fw_error %d)\n", + __func__, count, argp->error); + ret = -EIO; + } else if (count <= npages) { + params.gfn_start += count; + params.len -= count * PAGE_SIZE; + if (params.type != KVM_SEV_SNP_PAGE_TYPE_ZERO) + params.uaddr += count * PAGE_SIZE; + + ret = copy_to_user(u64_to_user_ptr(argp->data), ¶ms, sizeof(params)) + ? -EIO : 0; + } else { + WARN_ONCE(1, "Completed page count %ld exceeds requested amount %ld", + count, npages); + ret = -EINVAL; + } + +out: + mutex_unlock(&kvm->slots_lock); + + return ret; +} + int sev_mem_enc_ioctl(struct kvm *kvm, void __user *argp) { struct kvm_sev_cmd sev_cmd; @@ -2217,6 +2451,9 @@ int sev_mem_enc_ioctl(struct kvm *kvm, void __user *argp) case KVM_SEV_SNP_LAUNCH_START: r = snp_launch_start(kvm, &sev_cmd); break; + case KVM_SEV_SNP_LAUNCH_UPDATE: + r = snp_launch_update(kvm, &sev_cmd); + break; default: r = -EINVAL; goto out; -- 2.25.1