[PATCH v2 26/26] KVM: selftests: Map x86_64 guest virtual memory with huge pages

David Matlack
2022-03-11T00:26:27Z

Override virt_map() in x86_64 selftests to use the largest page size
possible when mapping guest virtual memory. This enables testing eager
page splitting with shadow paging (e.g. kvm_intel.ept=N), as it allows
KVM to shadow guest memory with huge pages.

Signed-off-by: David Matlack <dmatlack@google.com>
---
.../selftests/kvm/include/x86_64/processor.h | 6 ++++
tools/testing/selftests/kvm/lib/kvm_util.c | 4 +--
.../selftests/kvm/lib/x86_64/processor.c | 31 +++++++++++++++++++
3 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
index 37db341d4cc5..efb228d2fbf7 100644
--- a/tools/testing/selftests/kvm/include/x86_64/processor.h
+++ b/tools/testing/selftests/kvm/include/x86_64/processor.h
@@ -470,6 +470,12 @@ enum x86_page_size {
X86_PAGE_SIZE_2M,
X86_PAGE_SIZE_1G,
};
+
+static inline size_t page_size_bytes(enum x86_page_size page_size)
+{
+ return 1UL << (page_size * 9 + 12);
+}
+
void __virt_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
enum x86_page_size page_size);

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 1665a220abcb..60198587236d 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -1432,8 +1432,8 @@ vm_vaddr_t vm_vaddr_alloc_page(struct kvm_vm *vm)
* Within the VM given by @vm, creates a virtual translation for
* @npages starting at @vaddr to the page range starting at @paddr.
*/
-void virt_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
- unsigned int npages)
+void __weak virt_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
+ unsigned int npages)
{
size_t page_size = vm->page_size;
size_t size = npages * page_size;
diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
index 9f000dfb5594..7df84292d5de 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -282,6 +282,37 @@ void virt_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr)
__virt_pg_map(vm, vaddr, paddr, X86_PAGE_SIZE_4K);
}

+void virt_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr, unsigned int npages)
+{
+ size_t size = (size_t) npages * vm->page_size;
+ size_t vend = vaddr + size;
+ enum x86_page_size page_size;
+ size_t stride;
+
+ TEST_ASSERT(vaddr + size > vaddr, "Vaddr overflow");
+ TEST_ASSERT(paddr + size > paddr, "Paddr overflow");
+
+ /*
+ * Map the region with all 1G pages if possible, falling back to all
+ * 2M pages, and finally all 4K pages. This could be improved to use
+ * a mix of page sizes so that more of the region is mapped with large
+ * pages.
+ */
+ for (page_size = X86_PAGE_SIZE_1G; page_size >= X86_PAGE_SIZE_4K; page_size--) {
+ stride = page_size_bytes(page_size);
+
+ if (!(vaddr % stride) && !(paddr % stride) && !(size % stride))
+ break;
+ }
+
+ TEST_ASSERT(page_size >= X86_PAGE_SIZE_4K,
+ "Cannot map unaligned region: vaddr 0x%lx paddr 0x%lx npages 0x%x\n",
+ vaddr, paddr, npages);
+
+ for (; vaddr < vend; vaddr += stride, paddr += stride)
+ __virt_pg_map(vm, vaddr, paddr, page_size);
+}
+
static struct pageTableEntry *_vm_get_page_table_entry(struct kvm_vm *vm, int vcpuid,
uint64_t vaddr)
{
--
2.35.1.723.g4982287a31-goog