[PATCH v13 19/44] KVM: SEV: Make 'uaddr' parameter optional for KVM_SEV_SNP_LAUNCH_UPDATE
From: Ackerley Tng via B4 Relay <devnull+ackerleytng.google.com@kernel.org>
Date: 2026-09-10 23:55:39
Also in:
b4-sent, kvm, linux-coco, linux-doc, linux-kselftest, linux-mm, lkml
Subsystem:
documentation, kernel virtual machine (kvm), kernel virtual machine for x86 (kvm/x86), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Jonathan Corbet, Paolo Bonzini, Sean Christopherson, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
From: Michael Roth <redacted> Make the source page for populating an SNP guest_memfd instance optional if in-place conversion/population is enabled. If KVM can convert the page in-place, then it's possible for guest memory to be initialized directly from userspace by mmap()'ing the guest_memfd and writing to it while the corresponding GPA ranges are in a 'shared' state, before converting them to the 'private' state expected by KVM_SEV_SNP_LAUNCH_UPDATE. Update the handling/documentation for KVM_SEV_SNP_LAUNCH_UPDATE to allow for 'uaddr' to be set to NULL when in-place conversion is enabled, which SNP_LAUNCH_UPDATE will then use to determine when it should/shouldn't copy in data from a separate memory location. Continue to enforce non-NULL when PRIVATE is tracked per-VM, not per-guest_memfd. [ Sean: Moved condition to snp_launch_update ] Signed-off-by: Michael Roth <redacted> Signed-off-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Ackerley Tng <redacted> Tested-by: Shivank Garg <redacted> --- Documentation/virt/kvm/x86/amd-memory-encryption.rst | 14 ++++++++++---- arch/x86/kvm/svm/sev.c | 11 ++++++----- virt/kvm/kvm_main.c | 1 + 3 files changed, 17 insertions(+), 9 deletions(-)
diff --git a/Documentation/virt/kvm/x86/amd-memory-encryption.rst b/Documentation/virt/kvm/x86/amd-memory-encryption.rst
index bd04a908a8dbd..5977fbe33b98c 100644
--- a/Documentation/virt/kvm/x86/amd-memory-encryption.rst
+++ b/Documentation/virt/kvm/x86/amd-memory-encryption.rst@@ -503,7 +503,8 @@ 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. +for KVM_SET_MEMORY_ATTRIBUTES/KVM_SET_MEMORY_ATTRIBUTES2 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
@@ -511,9 +512,14 @@ range requested. Instead, the ``gfn_start``, ``uaddr``, and ``len`` fields of 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. +range plus 1, and ``uaddr`` (if specified) 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. For all other page types, ``uaddr`` is optional if in-place +conversion is enabled (i.e. when the data had been written directly to +guest_memfd while the page was in the shared state) and is required if in-place +conversion is disabled. Parameters (in): struct kvm_sev_snp_launch_update
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index dff684b88f153..63e8cfa9bf559 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c@@ -2400,7 +2400,7 @@ static int sev_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, */ if (ret && !snp_page_reclaim(kvm, pfn) && sev_populate_args->type == KVM_SEV_SNP_PAGE_TYPE_CPUID && - sev_populate_args->fw_error == SEV_RET_INVALID_PARAM) { + sev_populate_args->fw_error == SEV_RET_INVALID_PARAM && src_page) { void *src_vaddr = kmap_local_page(src_page); void *dst_vaddr = kmap_local_pfn(pfn);
@@ -2433,8 +2433,8 @@ static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp) 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); + pr_debug("%s: GFN start 0x%llx length 0x%llx type %d flags %d src %llx\n", __func__, + params.gfn_start, params.len, params.type, params.flags, params.uaddr); if (!params.len || !PAGE_ALIGNED(params.len) || params.flags || (params.type != KVM_SEV_SNP_PAGE_TYPE_NORMAL &&
@@ -2446,7 +2446,8 @@ static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp) if (params.type == KVM_SEV_SNP_PAGE_TYPE_ZERO) src = NULL; - else if (!params.uaddr || !PAGE_ALIGNED(params.uaddr)) + else if ((!gmem_in_place_conversion && !params.uaddr) || + !PAGE_ALIGNED(params.uaddr)) return -EINVAL; else src = u64_to_user_ptr(params.uaddr);
@@ -2493,7 +2494,7 @@ static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp) params.gfn_start += count; params.len -= count * PAGE_SIZE; - if (params.type != KVM_SEV_SNP_PAGE_TYPE_ZERO) + if (src && params.type != KVM_SEV_SNP_PAGE_TYPE_ZERO) params.uaddr += count * PAGE_SIZE; if (copy_to_user(u64_to_user_ptr(argp->data), ¶ms, sizeof(params)))
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 1ea8198821917..05c518c9b8078 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c@@ -104,6 +104,7 @@ module_param(allow_unsafe_mappings, bool, 0444); #ifdef kvm_arch_has_private_mem bool __ro_after_init gmem_in_place_conversion = false; +EXPORT_SYMBOL_FOR_KVM_INTERNAL(gmem_in_place_conversion); #endif /*
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2.55.0.1007.g17ff1f9808-goog