+ tools-add-selftests-to-hmm-for-cow-in-device-memory.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: tools: add selftests to hmm for COW in device memory
has been added to the -mm mm-unstable branch.  Its filename is
     tools-add-selftests-to-hmm-for-cow-in-device-memory.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/tools-add-selftests-to-hmm-for-cow-in-device-memory.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Alex Sierra <alex.sierra@amd.com>
Subject: tools: add selftests to hmm for COW in device memory
Date: Thu, 7 Jul 2022 14:03:49 -0500

The objective is to test device migration mechanism in pages marked as
COW, for private and coherent device type.  In case of writing to COW
private page(s), a page fault will migrate pages back to system memory
first.  Then, these pages will be duplicated.  In case of COW device
coherent type, pages are duplicated directly from device memory.

Link: https://lkml.kernel.org/r/20220707190349.9778-16-alex.sierra@amd.com
Signed-off-by: Alex Sierra <alex.sierra@amd.com>
Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/vm/hmm-tests.c |   80 +++++++++++++++++++++++
 1 file changed, 80 insertions(+)

--- a/tools/testing/selftests/vm/hmm-tests.c~tools-add-selftests-to-hmm-for-cow-in-device-memory
+++ a/tools/testing/selftests/vm/hmm-tests.c
@@ -1874,4 +1874,84 @@ TEST_F(hmm, hmm_gup_test)
 	close(gup_fd);
 	hmm_buffer_free(buffer);
 }
+
+/*
+ * Test copy-on-write in device pages.
+ * In case of writing to COW private page(s), a page fault will migrate pages
+ * back to system memory first. Then, these pages will be duplicated. In case
+ * of COW device coherent type, pages are duplicated directly from device
+ * memory.
+ */
+TEST_F(hmm, hmm_cow_in_device)
+{
+	struct hmm_buffer *buffer;
+	unsigned long npages;
+	unsigned long size;
+	unsigned long i;
+	int *ptr;
+	int ret;
+	unsigned char *m;
+	pid_t pid;
+	int status;
+
+	npages = 4;
+	size = npages << self->page_shift;
+
+	buffer = malloc(sizeof(*buffer));
+	ASSERT_NE(buffer, NULL);
+
+	buffer->fd = -1;
+	buffer->size = size;
+	buffer->mirror = malloc(size);
+	ASSERT_NE(buffer->mirror, NULL);
+
+	buffer->ptr = mmap(NULL, size,
+			   PROT_READ | PROT_WRITE,
+			   MAP_PRIVATE | MAP_ANONYMOUS,
+			   buffer->fd, 0);
+	ASSERT_NE(buffer->ptr, MAP_FAILED);
+
+	/* Initialize buffer in system memory. */
+	for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+		ptr[i] = i;
+
+	/* Migrate memory to device. */
+
+	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
+	ASSERT_EQ(ret, 0);
+	ASSERT_EQ(buffer->cpages, npages);
+
+	pid = fork();
+	if (pid == -1)
+		ASSERT_EQ(pid, 0);
+	if (!pid) {
+		/* Child process waitd for SIGTERM from the parent. */
+		while (1) {
+		}
+		perror("Should not reach this\n");
+		exit(0);
+	}
+	/* Parent process writes to COW pages(s) and gets a
+	 * new copy in system. In case of device private pages,
+	 * this write causes a migration to system mem first.
+	 */
+	for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+		ptr[i] = i;
+
+	/* Terminate child and wait */
+	EXPECT_EQ(0, kill(pid, SIGTERM));
+	EXPECT_EQ(pid, waitpid(pid, &status, 0));
+	EXPECT_NE(0, WIFSIGNALED(status));
+	EXPECT_EQ(SIGTERM, WTERMSIG(status));
+
+	/* Take snapshot to CPU pagetables */
+	ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_SNAPSHOT, buffer, npages);
+	ASSERT_EQ(ret, 0);
+	ASSERT_EQ(buffer->cpages, npages);
+	m = buffer->mirror;
+	for (i = 0; i < npages; i++)
+		ASSERT_EQ(HMM_DMIRROR_PROT_WRITE, m[i]);
+
+	hmm_buffer_free(buffer);
+}
 TEST_HARNESS_MAIN
_

Patches currently in -mm which might be from alex.sierra@amd.com are

mm-rename-is_pinnable_pages-to-is_longterm_pinnable_pages.patch
mm-move-page-zone-helpers-into-new-header-specific-file.patch
mm-add-zone-device-coherent-type-memory-support.patch
mm-handling-non-lru-pages-returned-by-vm_normal_pages.patch
mm-add-device-coherent-vma-selection-for-memory-migration.patch
drm-amdkfd-add-spm-support-for-svm.patch
lib-test_hmm-add-ioctl-to-get-zone-device-type.patch
lib-test_hmm-add-module-param-for-zone-device-type.patch
lib-add-support-for-device-coherent-type-in-test_hmm.patch
tools-update-hmm-test-to-support-device-coherent-type.patch
tools-update-test_hmm-script-to-support-sp-config.patch
tools-add-hmm-gup-tests-for-device-coherent-type.patch
tools-add-selftests-to-hmm-for-cow-in-device-memory.patch