linux-kernel - [PATCH v6 08/30] KVM: selftests: TDX: Update load_td_memory_region() for VM memory backed by guest memfd

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Message-ID: <20250414214801.2693294-9-sagis@google.com>
Date: Mon, 14 Apr 2025 14:47:37 -0700
From: Sagi Shahar <sagis@...gle.com>
To: linux-kselftest@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>, 
	Shuah Khan <shuah@...nel.org>, Sean Christopherson <seanjc@...gle.com>, 
	Ackerley Tng <ackerleytng@...gle.com>, Ryan Afranji <afranji@...gle.com>, 
	Andrew Jones <ajones@...tanamicro.com>, Isaku Yamahata <isaku.yamahata@...el.com>, 
	Erdem Aktas <erdemaktas@...gle.com>, Rick Edgecombe <rick.p.edgecombe@...el.com>, 
	Sagi Shahar <sagis@...gle.com>, Roger Wang <runanwang@...gle.com>, 
	Binbin Wu <binbin.wu@...ux.intel.com>, Oliver Upton <oliver.upton@...ux.dev>, 
	"Pratik R. Sampat" <pratikrajesh.sampat@....com>, Reinette Chatre <reinette.chatre@...el.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: [PATCH v6 08/30] KVM: selftests: TDX: Update load_td_memory_region()
 for VM memory backed by guest memfd

From: Ackerley Tng <ackerleytng@...gle.com>

If guest memory is backed by restricted memfd

+ UPM is being used, hence encrypted memory region has to be
  registered
+ Can avoid making a copy of guest memory before getting TDX to
  initialize the memory region

Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
Signed-off-by: Sagi Shahar <sagis@...gle.com>
---
 .../selftests/kvm/lib/x86/tdx/tdx_util.c      | 38 +++++++++++++++----
 1 file changed, 30 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c b/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c
index bb074af4a476..e2bf9766dc03 100644
--- a/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c
+++ b/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c
@@ -324,6 +324,21 @@ static void tdx_td_finalize_mr(struct kvm_vm *vm)
 	tdx_ioctl(vm->fd, KVM_TDX_FINALIZE_VM, 0, NULL);
 }
 
+/*
+ * Other ioctls
+ */
+
+/*
+ * Register a memory region that may contain encrypted data in KVM.
+ */
+static void register_encrypted_memory_region(struct kvm_vm *vm,
+					     struct userspace_mem_region *region)
+{
+	vm_set_memory_attributes(vm, region->region.guest_phys_addr,
+				 region->region.memory_size,
+				 KVM_MEMORY_ATTRIBUTE_PRIVATE);
+}
+
 /*
  * TD creation/setup/finalization
  */
@@ -459,28 +474,35 @@ static void load_td_memory_region(struct kvm_vm *vm,
 	if (!sparsebit_any_set(pages))
 		return;
 
+	if (region->region.guest_memfd != -1)
+		register_encrypted_memory_region(vm, region);
+
 	sparsebit_for_each_set_range(pages, i, j) {
 		const uint64_t size_to_load = (j - i + 1) * vm->page_size;
 		const uint64_t offset =
 			(i - lowest_page_in_region) * vm->page_size;
 		const uint64_t hva = hva_base + offset;
 		const uint64_t gpa = gpa_base + offset;
-		void *source_addr;
+		void *source_addr = (void *)hva;
 
 		/*
 		 * KVM_TDX_INIT_MEM_REGION ioctl cannot encrypt memory in place.
 		 * Make a copy if there's only one backing memory source.
 		 */
-		source_addr = mmap(NULL, size_to_load, PROT_READ | PROT_WRITE,
-				   MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
-		TEST_ASSERT(source_addr,
-			    "Could not allocate memory for loading memory region");
-
-		memcpy(source_addr, (void *)hva, size_to_load);
+		if (region->region.guest_memfd == -1) {
+			source_addr = mmap(NULL, size_to_load, PROT_READ | PROT_WRITE,
+					   MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+			TEST_ASSERT(source_addr,
+				    "Could not allocate memory for loading memory region");
+
+			memcpy(source_addr, (void *)hva, size_to_load);
+			memset((void *)hva, 0, size_to_load);
+		}
 
 		tdx_init_mem_region(vm, source_addr, gpa, size_to_load);
 
-		munmap(source_addr, size_to_load);
+		if (region->region.guest_memfd == -1)
+			munmap(source_addr, size_to_load);
 	}
 }
 
-- 
2.49.0.504.g3bcea36a83-goog