Re: [PATCH v7 20/42] KVM: SEV: Make 'uaddr' parameter optional for KVM_SEV_SNP_LAUNCH_UPDATE

---
  Documentation/virt/kvm/x86/amd-memory-encryption.rst | 15 +++++++++++----
  arch/x86/kvm/svm/sev.c                               | 18 +++++++++++++-----
  virt/kvm/kvm_main.c                                  |  1 +
  3 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/Documentation/virt/kvm/x86/amd-memory-encryption.rst b/Documentation/virt/kvm/x86/amd-memory-encryption.rst
index b2395dd4769de..43085f65b2d85 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 +512,15 @@ 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. Otherwise, ``uaddr`` is required if
+kvm.vm_memory_attributes=1 and optional if kvm.vm_memory_attributes=0, since
+in the latter case guest memory can be initialized directly from userspace
+prior to converting it to private and passing the GPA range on to this
+interface.

  
  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 1a361f08c7a3d..e1dbc827c2807 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c

@@ -2343,7 +2343,15 @@ static int sev_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn,
  	int level;
  	int ret;
  
-	if (WARN_ON_ONCE(sev_populate_args->type != KVM_SEV_SNP_PAGE_TYPE_ZERO && !src_page))
+	/*
+	 * For vm_memory_attributes=1, in-place conversion/population is not
+	 * supported, so the initial contents necessarily need to come from a
+	 * separate src address. For vm_memory_attributes=0, this isn't
+	 * necessarily the case, since the pages may have been populated
+	 * directly from userspace before calling KVM_SEV_SNP_LAUNCH_UPDATE.
+	 */
+	if (vm_memory_attributes &&
+	    sev_populate_args->type != KVM_SEV_SNP_PAGE_TYPE_ZERO && !src_page)
  		return -EINVAL;
  
  	ret = snp_lookup_rmpentry((u64)pfn, &assigned, &level);

@@ -2390,7 +2398,7 @@ 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);
  

@@ -2423,8 +2431,8 @@ static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp)
  	if (copy_from_user(&params, 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 &&

@@ -2481,7 +2489,7 @@ 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), &params, sizeof(params)))

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index ba195bb239aaa..3bf212fd99193 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c

@@ -105,6 +105,7 @@ module_param(allow_unsafe_mappings, bool, 0444);
  #ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
  bool vm_memory_attributes = true;
  module_param(vm_memory_attributes, bool, 0444);
+EXPORT_SYMBOL_FOR_KVM_INTERNAL(vm_memory_attributes);
  #endif
  DEFINE_STATIC_CALL_RET0(__kvm_get_memory_attributes, kvm_get_memory_attributes_t);
  EXPORT_SYMBOL_FOR_KVM_INTERNAL(STATIC_CALL_KEY(__kvm_get_memory_attributes));