[PATCH i-g-t v6 0/9] add cgroup_dmem test

[PATCH i-g-t v6 0/9] add cgroup_dmem test

[Thadeu Lima de Souza Cascardo]

v6 TLDR:
Change igt_dmem_driver API by moving handle array allocation out of it and
into the test itself and including dmem.max new behavior test.

This patchset is based on the work of Thomas Hellström at [1] and a
followup I have submitted at [2].

With this version, I reverted the order in which to apply the patchsets, as
this one adds the infrastructure and the drivers mechanisms, and a test for
dmem.current and its behavior around dmem.max that is currently supported
in the kernel.

As for the new dmem.max eviction behavior, introduced by [3], it has been
now included since it has been merged to Linux v7.3-rc1.

I have run the tests, including the ones that test dmem.max eviction
behavior on a system with a 1GiB VRAM amdgpu card. Rodrigo Siqueira helped
me run it on a Xe system. We have had applied the patchset at [3] on top of
then current linux origin/master [5], with a fixup for the amdgpu driver.

This latest version has not been tested on Xe, except for the dmem.current
behavior, which was tested with a 7.0 kernel.

Latest tests for amdgpu used v7.3-rc1.

Now, for the changes since v1 [2]:
- Changed the test name from drv_dmem_cgroups to dmem_cgroups.
- Have system includes before igt ones.
- Documented the current SUBTEST.
- Changed free_vram driver hook to only release a given BO. This allows for
  the eviction trigger by a new allocation added by write_eviction_nonblock
  subtest.
- Changed allocate_vram to keep more state necessary for releasing a single BO.
- Added a global free_vram helper to free all allocated VRAM.

Compared to v3 of [1]:
- I have kept wait_for_usage_drop as release can be lazy and we test for it
  on test_current SUBTEST, but had USAGE_DROP_TIMEOUT_MS be a little
  longer.
- Changed BO_SIZE and EVICT_STEP to allow for more than two eviction steps
  on a 1GiB VRAM system.
- Reduced USAGE_SLACK to avoid false positives, but still allow for some
  page table accounting.

Compared to v2 of this one [6]:

- Ignore -ENOMEM and -ENOSPC when trying to fill VRAM.
- When limiting max memory, allow for some slack, as there might be some
  overhead.
- On Xe, allocate GEM object with no deferred backing, and skip binding.

Compared to v3 of this one [7]:

- Merge dmem_cgroups tests into cgroup_dmem and making cgroup_dmem original
  test a subtest.
- Remove assertion when trying to verify allocations have failed as amdgpu
  will fallback to GTT.

Compared to v4 of this one [8]:
- Removed the creation of vm in Xe, that was leading to extra bytes being
  used and was no longer necessary.
- Removed the USAGE_SLACK that was necessary due to the extra bytes
  allocated due to the use of vm in Xe.

Compared to v5 of this one [10]:
- Documented igt_dmem_driver structure.
- Simplified igt_dmem_driver API, such that handle array allocation is not
  done, and handles are returned as part of allocation.
- Make get_region_name callback use the context, instead of fd, which
  avoids repeating the vram region lookup for Xe.
- Moved handle array allocation into the test.
- init/deinit the igt_dmem_driver per driver, not per subtest.

[1] https://patchwork.freedesktop.org/series/163935/#rev3
[2] https://patchwork.freedesktop.org/series/166496/
[3] https://lore.kernel.org/dri-devel/20260611173301.17473-1-thomas.hellstrom@linux.intel.com/
[4] https://gitlab.freedesktop.org/cascardo/igt-gpu-tools/-/commits/dmem_max?ref_type=heads
[5] 502d801f0ab0 ("Merge tag 'erofs-for-7.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs")
[6] https://lore.kernel.org/dri-devel/20260623174319.4138648-1-cascardo@igalia.com/
[7] https://lore.kernel.org/dri-devel/20260702130108.1397444-1-cascardo@igalia.com/
[8] https://lore.kernel.org/dri-devel/20260717120447.1837818-1-cascardo@igalia.com/
[9] https://lore.kernel.org/dri-devel/20260703130541.2686-1-thomas.hellstrom@linux.intel.com/
[10] https://lore.kernel.org/dri-devel/20260723194313.2748143-1-cascardo@igalia.com/

To: igt-dev@lists.freedesktop.org
Cc: siqueira@igalia.com
Cc: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Cc: dri-devel@lists.freedesktop.org
Cc: amd-gfx@lists.freedesktop.org
Cc: intel-xe@lists.freedesktop.org
Cc: Christian Koenig <christian.koenig@amd.com>
Cc: maarten.lankhorst@linux.intel.com
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Kamil Konieczny <kamil.konieczny@linux.intel.com>
Cc: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Cc: Vitaly Prosyak <vitaly.prosyak@amd.com>
Cc: Natalie Vock <natalie.vock@gmx.de>
Cc: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Cc: kernel-dev@igalia.com

--
2.47.3

---
Thadeu Lima de Souza Cascardo (4):
      lib/xe: Introduce dmem driver and implement Xe support
      lib/amdgpu: add amdgpu_cgroup_region_name
      lib/amdgpu: add amdgpu support to igt_dmem_driver
      tests/cgroup_dmem: add test for dmem.current

Thomas Hellström (5):
      lib/igt_cgroup: add cgroup v2 and dmem controller helpers
      tests/cgroup_dmem: add dmem cgroup controller test
      lib/xe: add xe_cgroup_region_name() helper
      tests/cgroup_dmem: add dmem cgroup eviction test
      tests/cgroup_dmem: add write_eviction_nonblock subtest

 lib/amdgpu/amd_dmem.c   |  90 +++++++
 lib/amdgpu/amd_memory.c |  25 ++
 lib/amdgpu/amd_memory.h |   2 +
 lib/igt.h               |   1 +
 lib/igt_cgroup.c        | 638 ++++++++++++++++++++++++++++++++++++++++++++++++
 lib/igt_cgroup.h        |  56 +++++
 lib/igt_dmem_driver.h   |  35 +++
 lib/meson.build         |   3 +
 lib/xe/xe_dmem.c        |  97 ++++++++
 lib/xe/xe_query.c       |  32 +++
 lib/xe/xe_query.h       |   2 +
 tests/cgroup_dmem.c     | 524 +++++++++++++++++++++++++++++++++++++++
 tests/meson.build       |   1 +
 13 files changed, 1506 insertions(+)
---
base-commit: aafc4bcf336167ad12356050b2e1da7e8c314555
change-id: 20260902-dmem_max-1a5e837347a8

Best regards,
--  
Thadeu Lima de Souza Cascardo <cascardo@igalia.com>

[PATCH i-g-t v6 1/9] lib/igt_cgroup: add cgroup v2 and dmem controller helpers

[Thadeu Lima de Souza Cascardo]

From: Thomas Hellström <thomas.hellstrom@linux.intel.com>

Add igt_cgroup, a library module providing helpers to create and manage
cgroup v2 sub-cgroups from IGT tests, with support for the dmem
controller that governs device memory (e.g. GPU VRAM) limits.

The API covers:
 - igt_cgroup_new() / igt_cgroup_free(): create and destroy a named
   sub-cgroup under the unified cgroupv2 hierarchy, enabling the dmem
   controller automatically.
 - igt_cgroup_move_current(): move the calling process into a cgroup.
 - igt_cgroup_dmem_set/get_max/min/low(): write and read dmem.max,
   dmem.min and dmem.low for a named device memory region.
 - igt_cgroup_dmem_get_current(): read current per-cgroup device memory
   usage.
 - igt_cgroup_dmem_get_system_current(): read system-wide device memory
   usage from the root cgroup.
 - igt_cgroup_dmem_get_capacity(): read total region capacity from the
   root cgroup's dmem.capacity file.
 - igt_cgroup_dmem_regions() / igt_cgroup_dmem_regions_free(): enumerate
   all registered device memory regions.

All public API functions that can fail use igt_assert internally rather
than returning error codes, following the IGT convention.

Assisted-by: GitHub Copilot:claude-sonnet-4.6
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 lib/igt.h        |   1 +
 lib/igt_cgroup.c | 638 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/igt_cgroup.h |  56 +++++
 lib/meson.build  |   1 +
 4 files changed, 696 insertions(+)

diff --git a/lib/igt.h b/lib/igt.h
index 173ca70bff28..d8e5de7dcd2f 100644
--- a/lib/igt.h
+++ b/lib/igt.h
@@ -27,6 +27,7 @@
 #include "drmtest.h"
 #include "i915_3d.h"
 #include "igt_aux.h"
+#include "igt_cgroup.h"
 #include "igt_configfs.h"
 #include "igt_core.h"
 #include "igt_debugfs.h"
diff --git a/lib/igt_cgroup.c b/lib/igt_cgroup.c
new file mode 100644
index 000000000000..60586ccc4861
--- /dev/null
+++ b/lib/igt_cgroup.c
@@ -0,0 +1,638 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2025 Intel Corporation
+ */
+
+/**
+ * SECTION:igt_cgroup
+ * @short_description: cgroup v2 helpers for IGT tests
+ * @title: cgroup
+ * @include: igt_cgroup.h
+ *
+ * This library provides helpers for creating and managing cgroup v2
+ * sub-cgroups from IGT tests, including support for the dmem controller
+ * which governs device memory (e.g. GPU VRAM) limits.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/statfs.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "igt_cgroup.h"
+#include "igt_core.h"
+#include "igt_fs.h"
+
+#ifndef CGROUP2_SUPER_MAGIC
+#define CGROUP2_SUPER_MAGIC 0x63677270
+#endif
+
+/**
+ * struct igt_cgroup - Opaque handle to a cgroup v2 sub-cgroup.
+ * @dirfd: File descriptor for the cgroup directory.
+ * @path: Absolute path to the cgroup directory.
+ * @parent_path: Absolute path to the parent cgroup directory.
+ *
+ * Allocated by igt_cgroup_new() and freed by igt_cgroup_free().
+ */
+struct igt_cgroup {
+	int dirfd;
+	char *path;
+	char *parent_path;
+};
+
+static const char *cgroupv2_mount(void)
+{
+	static const char *path;
+	static const char * const candidates[] = {
+		"/sys/fs/cgroup",
+		"/sys/fs/cgroup/unified",
+		NULL,
+	};
+	struct statfs st;
+	int i;
+
+	if (path)
+		return path;
+
+	for (i = 0; candidates[i]; i++) {
+		if (statfs(candidates[i], &st) == 0 &&
+		    (unsigned long)st.f_type == CGROUP2_SUPER_MAGIC) {
+			path = candidates[i];
+			return path;
+		}
+	}
+
+	return NULL;
+}
+
+/*
+ * Write "+controller" to @cgroup_path/cgroup.subtree_control to enable
+ * the named controller for children of that cgroup.
+ */
+static int enable_controller(const char *cgroup_path, const char *controller)
+{
+	char path[PATH_MAX];
+	char cmd[64];
+	ssize_t ret;
+	int fd;
+
+	snprintf(path, sizeof(path), "%s/cgroup.subtree_control", cgroup_path);
+	snprintf(cmd, sizeof(cmd), "+%s", controller);
+
+	fd = open(path, O_WRONLY);
+	if (fd < 0)
+		return -errno;
+
+	ret = write(fd, cmd, strlen(cmd));
+	close(fd);
+
+	return (ret < 0) ? -errno : 0;
+}
+
+/*
+ * Move every PID listed in @cgroup_path/cgroup.procs to
+ * @parent_path/cgroup.procs.  Silently ignores individual failures
+ * (a PID may have exited between reading and writing).
+ */
+static void drain_procs_to_parent(const char *cgroup_path,
+				  const char *parent_path)
+{
+	char proc_path[PATH_MAX];
+	char parent_procs[PATH_MAX];
+	int parent_fd;
+	FILE *f;
+	int pid;
+
+	snprintf(proc_path, sizeof(proc_path), "%s/cgroup.procs", cgroup_path);
+	snprintf(parent_procs, sizeof(parent_procs), "%s/cgroup.procs", parent_path);
+
+	parent_fd = open(parent_procs, O_WRONLY);
+	if (parent_fd < 0)
+		return;
+
+	f = fopen(proc_path, "r");
+	if (f) {
+		while (fscanf(f, "%d", &pid) == 1) {
+			char pidbuf[32];
+			ssize_t len = snprintf(pidbuf, sizeof(pidbuf), "%d", pid);
+
+			write(parent_fd, pidbuf, len);
+		}
+		fclose(f);
+	}
+
+	close(parent_fd);
+}
+
+/**
+ * igt_cgroup_new() - Create a new cgroup v2 sub-cgroup.
+ * @name: Name for the new cgroup directory.
+ *
+ * Creates a sub-cgroup named @name under the system's unified cgroupv2
+ * hierarchy.  The dmem controller is enabled in the parent's
+ * subtree_control so that igt_cgroup_dmem_set_max() and friends take effect
+ * immediately.
+ *
+ * Return: Pointer to an &struct igt_cgroup on success, %NULL on failure.
+ */
+struct igt_cgroup *igt_cgroup_new(const char *name)
+{
+	struct igt_cgroup *cg;
+	const char *mount;
+	int ret;
+
+	mount = cgroupv2_mount();
+	if (!mount) {
+		igt_debug("cgroup v2 not found\n");
+		return NULL;
+	}
+
+	cg = calloc(1, sizeof(*cg));
+	if (!cg)
+		return NULL;
+
+	cg->parent_path = strdup(mount);
+	if (!cg->parent_path)
+		goto err_free;
+
+	if (asprintf(&cg->path, "%s/%s", mount, name) < 0) {
+		cg->path = NULL;
+		goto err_parent;
+	}
+
+	/*
+	 * Try to enable the dmem controller in the parent's subtree_control.
+	 * Ignore EINVAL which the kernel returns when the controller is already
+	 * listed (i.e. already enabled).
+	 */
+	ret = enable_controller(mount, "dmem");
+	if (ret < 0 && ret != -EINVAL)
+		igt_debug("Failed to enable dmem controller in %s: %d\n",
+			  mount, ret);
+
+	if (mkdir(cg->path, 0755) < 0 && errno != EEXIST) {
+		igt_debug("Failed to create cgroup %s: %m\n", cg->path);
+		goto err_path;
+	}
+
+	cg->dirfd = open(cg->path, O_RDONLY | O_DIRECTORY);
+	if (cg->dirfd < 0) {
+		igt_debug("Failed to open cgroup dir %s: %m\n", cg->path);
+		goto err_rmdir;
+	}
+
+	return cg;
+
+err_rmdir:
+	rmdir(cg->path);
+err_path:
+	free(cg->path);
+err_parent:
+	free(cg->parent_path);
+err_free:
+	free(cg);
+	return NULL;
+}
+
+/**
+ * igt_cgroup_free() - Destroy a cgroup and release its resources.
+ * @cg: The cgroup to destroy.
+ *
+ * Moves any processes still running inside @cg back to the parent cgroup,
+ * removes the cgroup directory, and frees all associated memory.
+ * After this call @cg must not be used.
+ */
+void igt_cgroup_free(struct igt_cgroup *cg)
+{
+	if (!cg)
+		return;
+
+	drain_procs_to_parent(cg->path, cg->parent_path);
+
+	close(cg->dirfd);
+
+	if (rmdir(cg->path) < 0)
+		igt_debug("Failed to remove cgroup %s: %m\n", cg->path);
+
+	free(cg->path);
+	free(cg->parent_path);
+	free(cg);
+}
+
+/**
+ * igt_cgroup_move_current() - Move the calling process into a cgroup.
+ * @cg: Target cgroup.
+ *
+ * Writes the calling process's PID to @cg's cgroup.procs file, transferring
+ * it into the cgroup.  All threads of the process move together.
+ * Fails the test via igt_assert on error.
+ */
+void igt_cgroup_move_current(struct igt_cgroup *cg)
+{
+	char pidbuf[32];
+	ssize_t len;
+	int fd, ret;
+
+	len = snprintf(pidbuf, sizeof(pidbuf), "%d", (int)getpid());
+
+	fd = openat(cg->dirfd, "cgroup.procs", O_WRONLY);
+	igt_assert_f(fd >= 0, "Failed to open cgroup.procs: %m\n");
+
+	ret = write(fd, pidbuf, len);
+	close(fd);
+
+	igt_assert_f(ret == len, "Failed to write PID to cgroup.procs: %m\n");
+}
+
+/*
+ * Parse a single dmem interface file line of the form "region_name value\n"
+ * where value is either a decimal byte count or the string "max".
+ * Returns 0 and writes to *out on success, -EINVAL on parse error.
+ */
+static int dmem_parse_line(char *line, const char *region, uint64_t *out)
+{
+	char *space = strchr(line, ' ');
+
+	if (!space)
+		return -EINVAL;
+
+	*space = '\0';
+	if (strcmp(line, region) != 0)
+		return -ENOENT;
+
+	if (strcmp(space + 1, "max") == 0) {
+		*out = IGT_CGROUP_DMEM_MAX;
+		return 0;
+	}
+
+	errno = 0;
+	*out = strtoull(space + 1, &space, 10);
+	if (errno || *space != '\0')
+		return -EINVAL;
+
+	return 0;
+}
+
+/*
+ * Read a dmem interface file opened relative to @dirfd, searching for
+ * @region.  On success writes the region's value to @out and returns 0.
+ * Returns -ENOENT when @region is absent, or a negative errno otherwise.
+ */
+static int dmem_read_region(int dirfd, const char *file,
+			    const char *region, uint64_t *out)
+{
+	char buf[4096];
+	char *line, *saveptr;
+	ssize_t n;
+	int fd;
+
+	fd = openat(dirfd, file, O_RDONLY);
+	if (fd < 0)
+		return -errno;
+
+	n = igt_readn(fd, buf, sizeof(buf) - 1);
+	close(fd);
+	if (n < 0)
+		return (int)n;
+	buf[n] = '\0';
+
+	for (line = strtok_r(buf, "\n", &saveptr); line;
+	     line = strtok_r(NULL, "\n", &saveptr)) {
+		int ret = dmem_parse_line(line, region, out);
+
+		if (ret != -ENOENT)
+			return ret;
+	}
+
+	return -ENOENT;
+}
+
+/*
+ * Write "region_name value" (or "region_name max") to the dmem interface
+ * file @file opened relative to @dirfd.
+ * If @nonblock is true the file is opened with O_NONBLOCK, causing any
+ * eviction triggered by the limit change to be skipped rather than waited
+ * for; the write still succeeds (returns 0).
+ * Returns 0 on success, negative errno on failure.
+ */
+static int dmem_write_region(int dirfd, const char *file,
+			     const char *region, uint64_t bytes, bool nonblock)
+{
+	char buf[PATH_MAX + 64];
+	ssize_t len;
+	int fd, ret;
+	int flags = O_WRONLY;
+
+	if (bytes == IGT_CGROUP_DMEM_MAX)
+		len = snprintf(buf, sizeof(buf), "%s max", region);
+	else
+		len = snprintf(buf, sizeof(buf), "%s %" PRIu64, region, bytes);
+
+	if (nonblock)
+		flags |= O_NONBLOCK;
+
+	fd = openat(dirfd, file, flags);
+	if (fd < 0)
+		return -errno;
+
+	do {
+		ret = write(fd, buf, len);
+		if (ret < 0 && errno == EINTR)
+			igt_debug("dmem cgroup write interrupted by signal, retrying\n");
+	} while (ret < 0 && errno == EINTR);
+	close(fd);
+
+	return (ret < 0) ? -errno : 0;
+}
+
+/**
+ * igt_cgroup_dmem_set_max() - Set the hard device memory limit for a region.
+ * @cg: Target cgroup.
+ * @region: Device memory region name (e.g. "drm/0000:03:00.0/vram0").
+ * @bytes: Hard limit in bytes.  Use %IGT_CGROUP_DMEM_MAX for no limit.
+ * @nonblock: If true, open the file with O_NONBLOCK so that eviction
+ *            triggered by the limit change is skipped rather than awaited.
+ *
+ * Writes @bytes to dmem.max for @region inside @cg.  Allocation attempts
+ * that would push usage past this limit fail with -EAGAIN in the kernel.
+ * Fails the test via igt_assert on error.
+ */
+void igt_cgroup_dmem_set_max(struct igt_cgroup *cg, const char *region,
+			     uint64_t bytes, bool nonblock)
+{
+	igt_assert_f(dmem_write_region(cg->dirfd, "dmem.max", region, bytes,
+				       nonblock) == 0,
+		     "Failed to set dmem.max for region %s\n", region);
+}
+
+/**
+ * igt_cgroup_dmem_set_min() - Set the hard protection threshold for a region.
+ * @cg: Target cgroup.
+ * @region: Device memory region name.
+ * @bytes: Hard protection threshold in bytes.  Pass 0 to disable.
+ *
+ * Writes @bytes to dmem.min for @region inside @cg.  Device memory below
+ * this threshold is never reclaimed regardless of system pressure.
+ * Fails the test via igt_assert on error.
+ */
+void igt_cgroup_dmem_set_min(struct igt_cgroup *cg, const char *region,
+			     uint64_t bytes)
+{
+	igt_assert_f(dmem_write_region(cg->dirfd, "dmem.min", region, bytes,
+				       false) == 0,
+		     "Failed to set dmem.min for region %s\n", region);
+}
+
+/**
+ * igt_cgroup_dmem_set_low() - Set the soft protection threshold for a region.
+ * @cg: Target cgroup.
+ * @region: Device memory region name.
+ * @bytes: Soft protection threshold in bytes.  Pass 0 to disable.
+ *
+ * Writes @bytes to dmem.low for @region inside @cg.  Device memory below
+ * this threshold is only reclaimed when no unprotected memory remains.
+ * Fails the test via igt_assert on error.
+ */
+void igt_cgroup_dmem_set_low(struct igt_cgroup *cg, const char *region,
+			     uint64_t bytes)
+{
+	igt_assert_f(dmem_write_region(cg->dirfd, "dmem.low", region, bytes,
+				       false) == 0,
+		     "Failed to set dmem.low for region %s\n", region);
+}
+
+/**
+ * igt_cgroup_dmem_get_current() - Read current device memory usage for a region.
+ * @cg: Target cgroup.
+ * @region: Device memory region name.
+ * @out: Receives the current usage in bytes.
+ *
+ * Reads dmem.current from @cg and returns the usage for @region.
+ * Fails the test via igt_assert on error.
+ */
+void igt_cgroup_dmem_get_current(struct igt_cgroup *cg, const char *region,
+				 uint64_t *out)
+{
+	igt_assert_f(dmem_read_region(cg->dirfd, "dmem.current", region, out) == 0,
+		     "Failed to read dmem.current for region %s\n", region);
+}
+
+/**
+ * igt_cgroup_dmem_get_max() - Read the configured hard limit for a region.
+ * @cg: Target cgroup.
+ * @region: Device memory region name.
+ * @out: Receives the limit in bytes, or %IGT_CGROUP_DMEM_MAX if unset.
+ *
+ * Reads dmem.max from @cg for @region.
+ * Fails the test via igt_assert on error.
+ */
+void igt_cgroup_dmem_get_max(struct igt_cgroup *cg, const char *region,
+			     uint64_t *out)
+{
+	igt_assert_f(dmem_read_region(cg->dirfd, "dmem.max", region, out) == 0,
+		     "Failed to read dmem.max for region %s\n", region);
+}
+
+/**
+ * igt_cgroup_dmem_get_min() - Read the configured hard protection threshold for a region.
+ * @cg: Target cgroup.
+ * @region: Device memory region name.
+ * @out: Receives the threshold in bytes.
+ *
+ * Reads dmem.min from @cg for @region.
+ * Fails the test via igt_assert on error.
+ */
+void igt_cgroup_dmem_get_min(struct igt_cgroup *cg, const char *region,
+			     uint64_t *out)
+{
+	igt_assert_f(dmem_read_region(cg->dirfd, "dmem.min", region, out) == 0,
+		     "Failed to read dmem.min for region %s\n", region);
+}
+
+/**
+ * igt_cgroup_dmem_get_low() - Read the configured soft protection threshold for a region.
+ * @cg: Target cgroup.
+ * @region: Device memory region name.
+ * @out: Receives the threshold in bytes.
+ *
+ * Reads dmem.low from @cg for @region.
+ * Fails the test via igt_assert on error.
+ */
+void igt_cgroup_dmem_get_low(struct igt_cgroup *cg, const char *region,
+			     uint64_t *out)
+{
+	igt_assert_f(dmem_read_region(cg->dirfd, "dmem.low", region, out) == 0,
+		     "Failed to read dmem.low for region %s\n", region);
+}
+
+/**
+ * igt_cgroup_dmem_available() - Check if the dmem cgroup controller is available.
+ *
+ * Probes the cgroup v2 hierarchy for the presence of a dmem.capacity file at
+ * the root, indicating that the kernel dmem controller is compiled in and at
+ * least one device memory region has been registered.
+ *
+ * Return: %true if the dmem controller is available, %false otherwise.
+ */
+bool igt_cgroup_dmem_available(void)
+{
+	char **regions = igt_cgroup_dmem_regions();
+
+	if (!regions)
+		return false;
+
+	igt_cgroup_dmem_regions_free(regions);
+	return true;
+}
+
+/**
+ * igt_cgroup_dmem_regions() - Enumerate all registered device memory regions.
+ *
+ * Reads the root cgroup's dmem.capacity file and returns a NULL-terminated
+ * array of region name strings.  Each name can be passed directly to
+ * igt_cgroup_dmem_get_capacity(), igt_cgroup_dmem_get_current(), and the
+ * igt_cgroup_dmem_set_*() / igt_cgroup_dmem_get_*() family.
+ *
+ * Free the returned array with igt_cgroup_dmem_regions_free().
+ *
+ * Return: A NULL-terminated array of strings on success, %NULL if cgroupv2
+ * is unavailable or no regions are registered.
+ */
+char **igt_cgroup_dmem_regions(void)
+{
+	char buf[4096];
+	char *line, *saveptr, *space, *name;
+	char **regions = NULL, **tmp;
+	int count = 0;
+	const char *mount;
+	ssize_t n;
+	int dirfd, fd;
+
+	mount = cgroupv2_mount();
+	if (!mount)
+		return NULL;
+
+	dirfd = open(mount, O_RDONLY | O_DIRECTORY);
+	if (dirfd < 0)
+		return NULL;
+
+	fd = openat(dirfd, "dmem.capacity", O_RDONLY);
+	close(dirfd);
+	if (fd < 0)
+		return NULL;
+
+	n = igt_readn(fd, buf, sizeof(buf) - 1);
+	close(fd);
+	if (n <= 0)
+		return NULL;
+	buf[n] = '\0';
+
+	for (line = strtok_r(buf, "\n", &saveptr); line;
+	     line = strtok_r(NULL, "\n", &saveptr)) {
+		space = strchr(line, ' ');
+
+		if (!space)
+			continue;
+		*space = '\0';
+
+		name = strdup(line);
+		if (!name)
+			goto err;
+
+		tmp = realloc(regions, (count + 2) * sizeof(*regions));
+		if (!tmp) {
+			free(name);
+			goto err;
+		}
+		regions = tmp;
+		regions[count++] = name;
+		regions[count] = NULL;
+	}
+
+	return regions;
+
+err:
+	igt_cgroup_dmem_regions_free(regions);
+	return NULL;
+}
+
+/**
+ * igt_cgroup_dmem_regions_free() - Free a region list returned by igt_cgroup_dmem_regions().
+ * @regions: NULL-terminated array returned by igt_cgroup_dmem_regions().
+ *
+ * Frees each string in @regions and the array itself.  Safe to call with
+ * %NULL.
+ */
+void igt_cgroup_dmem_regions_free(char **regions)
+{
+	int i;
+
+	if (!regions)
+		return;
+
+	for (i = 0; regions[i]; i++)
+		free(regions[i]);
+
+	free(regions);
+}
+
+/**
+ * igt_cgroup_dmem_get_capacity() - Read total device memory capacity for a region.
+ * @region: Device memory region name.
+ * @out: Receives the total capacity in bytes.
+ *
+ * Reads dmem.capacity from the root cgroup and returns the capacity for
+ * @region.  This reflects the maximum allocatable bytes, excluding memory
+ * reserved by the kernel for internal use.
+ * Fails the test via igt_assert on error.
+ */
+void igt_cgroup_dmem_get_capacity(const char *region, uint64_t *out)
+{
+	const char *mount;
+	int dirfd, ret;
+
+	mount = cgroupv2_mount();
+	igt_assert_f(mount, "cgroup v2 not available\n");
+
+	dirfd = open(mount, O_RDONLY | O_DIRECTORY);
+	igt_assert_f(dirfd >= 0, "Failed to open cgroup root: %m\n");
+
+	ret = dmem_read_region(dirfd, "dmem.capacity", region, out);
+	close(dirfd);
+
+	igt_assert_f(ret == 0, "Failed to read dmem.capacity for region %s\n", region);
+}
+
+/**
+ * igt_cgroup_dmem_get_system_current() - Read system-wide device memory usage for a region.
+ * @region: Device memory region name.
+ * @out: Receives the total system-wide usage in bytes.
+ *
+ * Reads dmem.current from the root cgroup for @region.  This reflects the
+ * aggregate device memory usage across all cgroups on the system.
+ * Fails the test via igt_assert on error.
+ */
+void igt_cgroup_dmem_get_system_current(const char *region, uint64_t *out)
+{
+	const char *mount;
+	int dirfd, ret;
+
+	mount = cgroupv2_mount();
+	igt_assert_f(mount, "cgroup v2 not available\n");
+
+	dirfd = open(mount, O_RDONLY | O_DIRECTORY);
+	igt_assert_f(dirfd >= 0, "Failed to open cgroup root: %m\n");
+
+	ret = dmem_read_region(dirfd, "dmem.current", region, out);
+	close(dirfd);
+
+	igt_assert_f(ret == 0, "Failed to read root dmem.current for region %s\n", region);
+}
diff --git a/lib/igt_cgroup.h b/lib/igt_cgroup.h
new file mode 100644
index 000000000000..379de457a54d
--- /dev/null
+++ b/lib/igt_cgroup.h
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2025 Intel Corporation
+ */
+
+#ifndef __IGT_CGROUP_H__
+#define __IGT_CGROUP_H__
+
+#include <stdbool.h>
+#include <stdint.h>
+
+/**
+ * IGT_CGROUP_DMEM_MAX - Sentinel value meaning "no device memory limit".
+ *
+ * Pass this to igt_cgroup_dmem_set_max() to remove a previously set limit,
+ * equivalent to writing "max" to the dmem.max interface file.
+ */
+#define IGT_CGROUP_DMEM_MAX UINT64_MAX
+
+/**
+ * struct igt_cgroup - Opaque handle to a cgroup v2 sub-cgroup.
+ *
+ * Allocated by igt_cgroup_new() and freed by igt_cgroup_free().
+ * All other functions in this module take a pointer to this type.
+ */
+struct igt_cgroup;
+
+struct igt_cgroup *igt_cgroup_new(const char *name);
+void igt_cgroup_free(struct igt_cgroup *cg);
+
+void igt_cgroup_move_current(struct igt_cgroup *cg);
+
+void igt_cgroup_dmem_set_max(struct igt_cgroup *cg, const char *region,
+			     uint64_t bytes, bool nonblock);
+void igt_cgroup_dmem_set_min(struct igt_cgroup *cg, const char *region,
+			     uint64_t bytes);
+void igt_cgroup_dmem_set_low(struct igt_cgroup *cg, const char *region,
+			     uint64_t bytes);
+
+void igt_cgroup_dmem_get_max(struct igt_cgroup *cg, const char *region,
+			     uint64_t *out);
+void igt_cgroup_dmem_get_min(struct igt_cgroup *cg, const char *region,
+			     uint64_t *out);
+void igt_cgroup_dmem_get_low(struct igt_cgroup *cg, const char *region,
+			     uint64_t *out);
+
+void igt_cgroup_dmem_get_current(struct igt_cgroup *cg, const char *region,
+				 uint64_t *out);
+void igt_cgroup_dmem_get_capacity(const char *region, uint64_t *out);
+void igt_cgroup_dmem_get_system_current(const char *region, uint64_t *out);
+
+bool igt_cgroup_dmem_available(void);
+char **igt_cgroup_dmem_regions(void);
+void igt_cgroup_dmem_regions_free(char **regions);
+
+#endif /* __IGT_CGROUP_H__ */
diff --git a/lib/meson.build b/lib/meson.build
index a7cde027ed04..b7e1be61d844 100644
--- a/lib/meson.build
+++ b/lib/meson.build
@@ -19,6 +19,7 @@ lib_sources = [
 	'i915/i915_dp.c',
 	'igt_collection.c',
 	'igt_color_encoding.c',
+	'igt_cgroup.c',
 	'igt_configfs.c',
 	'igt_facts.c',
 	'igt_crc.c',

-- 
2.47.3

[PATCH i-g-t v6 2/9] tests/cgroup_dmem: add dmem cgroup controller test

[Thadeu Lima de Souza Cascardo]

From: Thomas Hellström <thomas.hellstrom@linux.intel.com>

Add a test that exercises the cgroup v2 dmem controller interface using
the new igt_cgroup library.

The test uses igt_simple_main and:
  - Skips if no dmem regions are registered (no cgroup v2 or no
   dmem-capable device).
  - Creates a sub-cgroup and moves the test process into it.
  - Enumerates all registered device memory regions and prints their
   capacity, system-wide current usage, per-cgroup current usage, and
   configured min, low and max limits.
  - Destroys the cgroup on completion.

Assisted-by: GitHub Copilot:claude-sonnet-4.6
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 tests/cgroup_dmem.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 tests/meson.build   |  1 +
 2 files changed, 93 insertions(+)

diff --git a/tests/cgroup_dmem.c b/tests/cgroup_dmem.c
new file mode 100644
index 000000000000..442c965f9bbf
--- /dev/null
+++ b/tests/cgroup_dmem.c
@@ -0,0 +1,92 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2025 Intel Corporation
+ */
+
+/**
+ * TEST: cgroup dmem
+ * Description: Exercises the cgroup v2 dmem controller interface.  Creates a
+ *              cgroup, moves the process into it, enumerates all dmem regions,
+ *              prints their capacity, system-wide current usage, per-cgroup
+ *              current usage and configured limits, then destroys the cgroup.
+ * Category: Core
+ * Mega feature: General Core features
+ * Sub-category: uapi
+ * Functionality: cgroup
+ * Feature: dmem
+ * Test category: uapi
+ */
+
+#include <inttypes.h>
+
+#include "igt.h"
+#include "igt_cgroup.h"
+
+IGT_TEST_DESCRIPTION("Exercises the cgroup v2 dmem controller interface.");
+
+static void fmt_bytes(uint64_t v, char *buf, size_t len)
+{
+	if (v == IGT_CGROUP_DMEM_MAX)
+		snprintf(buf, len, "max");
+	else
+		snprintf(buf, len, "%" PRIu64, v);
+}
+
+int igt_simple_main()
+{
+	struct igt_cgroup *cg;
+	const char *region;
+	char **regions;
+	uint64_t capacity, sys_current, cg_current, min, low, max;
+	char cap_s[32], sys_s[32], cg_s[32];
+	char min_s[32], low_s[32], max_s[32];
+	int i;
+
+	igt_require_f(igt_cgroup_dmem_available(),
+		      "No dmem regions found; is cgroup v2 with the "
+		      "dmem controller available?\n");
+
+	cg = igt_cgroup_new("igt-cgroup-dmem-test");
+	igt_assert_f(cg, "Failed to create cgroup\n");
+
+	igt_cgroup_move_current(cg);
+
+	regions = igt_cgroup_dmem_regions();
+	igt_assert_f(regions, "Failed to enumerate dmem regions\n");
+
+	igt_info("%-40s %16s %16s %16s %16s %16s %16s\n",
+		 "region", "capacity", "system-current",
+		 "cgroup-current", "min", "low", "max");
+	igt_info("%-40s %16s %16s %16s %16s %16s %16s\n",
+		 "------", "--------", "--------------",
+		 "--------------", "---", "---", "---");
+
+	for (i = 0; regions[i]; i++) {
+		region = regions[i];
+
+		igt_cgroup_dmem_get_capacity(region, &capacity);
+		fmt_bytes(capacity, cap_s, sizeof(cap_s));
+
+		igt_cgroup_dmem_get_system_current(region, &sys_current);
+		fmt_bytes(sys_current, sys_s, sizeof(sys_s));
+
+		igt_cgroup_dmem_get_current(cg, region, &cg_current);
+		fmt_bytes(cg_current, cg_s, sizeof(cg_s));
+
+		igt_cgroup_dmem_get_min(cg, region, &min);
+		fmt_bytes(min, min_s, sizeof(min_s));
+
+		igt_cgroup_dmem_get_low(cg, region, &low);
+		fmt_bytes(low, low_s, sizeof(low_s));
+
+		igt_cgroup_dmem_get_max(cg, region, &max);
+		fmt_bytes(max, max_s, sizeof(max_s));
+
+		igt_info("%-40s %16s %16s %16s %16s %16s %16s\n",
+			 region, cap_s, sys_s, cg_s,
+			 min_s, low_s, max_s);
+	}
+
+	igt_cgroup_dmem_regions_free(regions);
+	igt_cgroup_free(cg);
+}
diff --git a/tests/meson.build b/tests/meson.build
index 1ac89bab7e15..c362d42888ba 100644
--- a/tests/meson.build
+++ b/tests/meson.build
@@ -1,4 +1,5 @@
 test_progs = [
+	'cgroup_dmem',
 	'core_auth',
 	'core_debugfs',
 	'core_getclient',

-- 
2.47.3

[PATCH i-g-t v6 3/9] lib/xe: add xe_cgroup_region_name() helper

[Thadeu Lima de Souza Cascardo]

From: Thomas Hellström <thomas.hellstrom@linux.intel.com>

Add xe_cgroup_region_name(fd, region) which constructs the dmem cgroup
region path for a given xe memory region.  The returned string has the
form "drm/<pci-slot>/<region>" (e.g. "drm/0000:03:00.0/vram0"),
matching the name registered by the kernel via drmm_cgroup_register_region().

Only VRAM regions are tracked by the dmem controller; system and stolen
memory regions return NULL.

Assisted-by: GitHub Copilot:claude-sonnet-4.6
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 lib/xe/xe_query.c | 32 ++++++++++++++++++++++++++++++++
 lib/xe/xe_query.h |  2 ++
 2 files changed, 34 insertions(+)

diff --git a/lib/xe/xe_query.c b/lib/xe/xe_query.c
index 68e60ddc75a2..e2b25be21140 100644
--- a/lib/xe/xe_query.c
+++ b/lib/xe/xe_query.c
@@ -7,6 +7,7 @@
  */
 
 #include <fcntl.h>
+#include <limits.h>
 #include <stdlib.h>
 #include <pthread.h>
 
@@ -21,6 +22,7 @@
 
 #include "drmtest.h"
 #include "igt_debugfs.h"
+#include "igt_device.h"
 #include "ioctl_wrappers.h"
 #include "igt_map.h"
 #include "intel_common.h"
@@ -1304,6 +1306,36 @@ int xe_query_eu_thread_count(int fd, int gt)
 		xe_hwconfig_lookup_value_u32(fd, INTEL_HWCONFIG_NUM_THREADS_PER_EU);
 }
 
+/**
+ * xe_cgroup_region_name() - Build the dmem cgroup region name for an xe memory region.
+ * @fd: xe device fd.
+ * @region: Region mask (as used by xe_mem_region(), xe_region_name(), etc.).
+ *
+ * Constructs the full dmem cgroup region path for @region on the device
+ * identified by @fd.  The returned string has the form
+ * ``drm/<pci-slot>/<region>`` (e.g. ``drm/0000:03:00.0/vram0``), matching
+ * the name registered by the kernel driver via drmm_cgroup_register_region().
+ *
+ * Only VRAM regions are registered with the dmem controller; passing a
+ * system-memory region returns %NULL.
+ *
+ * Return: A newly allocated string that the caller must free(), or %NULL if
+ * @region is not tracked by the dmem cgroup controller.
+ */
+char *xe_cgroup_region_name(int fd, uint64_t region)
+{
+	char pci_slot[NAME_MAX];
+	char *name;
+
+	if (xe_region_class(fd, region) != DRM_XE_MEM_REGION_CLASS_VRAM)
+		return NULL;
+
+	igt_device_get_pci_slot_name(fd, pci_slot);
+
+	igt_assert(asprintf(&name, "drm/%s/%s", pci_slot, xe_region_name(region)) > 0);
+	return name;
+}
+
 igt_constructor
 {
 	xe_device_cache_init();
diff --git a/lib/xe/xe_query.h b/lib/xe/xe_query.h
index 59330d80fd1b..a6ef9cab9aa1 100644
--- a/lib/xe/xe_query.h
+++ b/lib/xe/xe_query.h
@@ -206,4 +206,6 @@ void xe_device_put(int fd);
 int xe_query_eu_count(int fd, int gt);
 int xe_query_eu_thread_count(int fd, int gt);
 
+char *xe_cgroup_region_name(int fd, uint64_t region);
+
 #endif	/* XE_QUERY_H */

-- 
2.47.3

[PATCH i-g-t v6 4/9] lib/xe: Introduce dmem driver and implement Xe support

[Thadeu Lima de Souza Cascardo]

In order to be reuse the same dmem tests with multiple drivers, we need to
abstract a few operations. That includes getting the region name, and
allocating and releasing VRAM. As there is some initialization also when
multiple allocations are done, also provide init and deinit functions.

The Xe implementation was based on the original operations from
xe_cgroups.c written by Thomas Hellström. However, instead of doing a
deferred backing, followed by a bind, it does a simple non-deferred GEM
object creation on the VRAM region.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
---
 lib/igt_dmem_driver.h | 34 ++++++++++++++++++
 lib/meson.build       |  1 +
 lib/xe/xe_dmem.c      | 97 +++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 132 insertions(+)

diff --git a/lib/igt_dmem_driver.h b/lib/igt_dmem_driver.h
new file mode 100644
index 000000000000..e6998387eff9
--- /dev/null
+++ b/lib/igt_dmem_driver.h
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright 2026 Valve Corporation
+ * Authors:
+ *  Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
+ */
+
+#ifndef __IGT_DMEM_DRIVER_H__
+#define __IGT_DMEM_DRIVER_H__
+
+#include <stdlib.h>
+
+/**
+ * struct igt_dmem_driver - vendor driver to allocate and free device memory
+ *
+ */
+struct igt_dmem_driver {
+	/** @name: Driver name */
+	const char *name;
+	/** @init: Initialize an opaque context given a DRM device fd */
+	int (*init)(void **ctx, int fd);
+	/** @deinit: Release resources associated with context */
+	void (*deinit)(void *ctx);
+	/** @get_region_name: Return expected region name at dmem cgroup files */
+	char * (*get_region_name)(void *ctx);
+	/** @allocate_vram: Allocate @len sized vram and return an opaque @handle */
+	int (*allocate_vram)(void *ctx, size_t len, void **handle);
+	/** @free_vram: Free vram associated with @handle */
+	void (*free_vram)(void *ctx, void *handle);
+};
+
+extern const struct igt_dmem_driver xe_dmem_driver;
+
+#endif
diff --git a/lib/meson.build b/lib/meson.build
index b7e1be61d844..022408ce6864 100644
--- a/lib/meson.build
+++ b/lib/meson.build
@@ -130,6 +130,7 @@ lib_sources = [
 	'igt_dsc.c',
 	'igt_hook.c',
 	'xe/xe_device.c',
+	'xe/xe_dmem.c',
 	'xe/xe_ggtt.c',
 	'xe/xe_gt.c',
 	'xe/xe_ioctl.c',
diff --git a/lib/xe/xe_dmem.c b/lib/xe/xe_dmem.c
new file mode 100644
index 000000000000..628c905997d4
--- /dev/null
+++ b/lib/xe/xe_dmem.c
@@ -0,0 +1,97 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright 2026 Valve Corporation
+ * Authors:
+ *  Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
+ */
+
+#include <errno.h>
+
+#include "igt.h"
+#include "igt_cgroup.h"
+#include "igt_dmem_driver.h"
+#include "xe_drm.h"
+#include "xe/xe_ioctl.h"
+#include "xe/xe_query.h"
+
+struct xe_dmem_ctx {
+	int fd;
+	uint64_t vram_region;
+};
+
+static int xe_dmem_init(void **ctx, int fd)
+{
+	struct xe_dmem_ctx *xe_ctx;
+	uint64_t region;
+
+	xe_ctx = malloc(sizeof(*xe_ctx));
+	if (!xe_ctx)
+		return -ENOMEM;
+
+	xe_ctx->vram_region = 0;
+	/* Find first VRAM region */
+	xe_for_each_mem_region(fd, all_memory_regions(fd), region) {
+		if (xe_region_class(fd, region) == DRM_XE_MEM_REGION_CLASS_VRAM) {
+			xe_ctx->vram_region = region;
+			break;
+		}
+	}
+	if (!xe_ctx->vram_region)
+		goto out;
+
+	xe_ctx->fd = fd;
+
+	*ctx = xe_ctx;
+
+	return 0;
+
+out:
+	free(xe_ctx);
+
+	return -ENOMEM;
+}
+
+static void xe_dmem_deinit(void *ctx)
+{
+	struct xe_dmem_ctx *xe_ctx = ctx;
+
+	free(xe_ctx);
+}
+
+static char * xe_dmem_get_region_name(void *ctx)
+{
+	struct xe_dmem_ctx *xe_ctx = ctx;
+
+	return xe_cgroup_region_name(xe_ctx->fd, xe_ctx->vram_region);
+}
+
+static int xe_dmem_allocate_vram(void *ctx, size_t len, void **ret_handle)
+{
+	struct xe_dmem_ctx *xe_ctx = ctx;
+	uint32_t handle;
+	int err;
+
+	err = __xe_bo_create(xe_ctx->fd, 0, len, xe_ctx->vram_region, 0,
+			     NULL, &handle);
+	if (err)
+		return err;
+
+	*ret_handle = (void *)(uintptr_t) handle;
+	return 0;
+}
+
+static void xe_dmem_free_vram(void *ctx, void *handle)
+{
+	struct xe_dmem_ctx *xe_ctx = ctx;
+
+	gem_close(xe_ctx->fd, (uint32_t)(uintptr_t) handle);
+}
+
+const struct igt_dmem_driver xe_dmem_driver = {
+	.name = "xe",
+	.get_region_name = xe_dmem_get_region_name,
+	.init = xe_dmem_init,
+	.deinit = xe_dmem_deinit,
+	.allocate_vram = xe_dmem_allocate_vram,
+	.free_vram = xe_dmem_free_vram,
+};

-- 
2.47.3

[PATCH i-g-t v6 5/9] lib/amdgpu: add amdgpu_cgroup_region_name

[Thadeu Lima de Souza Cascardo]

The amdgpu dmem region name uses its PCI address, just like the one from
Xe, but there is only a single VRAM region.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
---
 lib/amdgpu/amd_memory.c | 25 +++++++++++++++++++++++++
 lib/amdgpu/amd_memory.h |  2 ++
 2 files changed, 27 insertions(+)

diff --git a/lib/amdgpu/amd_memory.c b/lib/amdgpu/amd_memory.c
index 12fe23c65ab2..2da4a8a4baee 100644
--- a/lib/amdgpu/amd_memory.c
+++ b/lib/amdgpu/amd_memory.c
@@ -30,9 +30,11 @@
 #include <amdgpu_drm.h>
 #include <stdio.h>
 #include <string.h>
+#include <limits.h>
 #include <unistd.h>
 #include <sys/mman.h>
 #include <inttypes.h>
+#include "igt_device.h"
 
 /**
  *
@@ -679,6 +681,29 @@ bool virtual_free_memory(void *address, unsigned int size)
 	}
 }
 
+/**
+ * amdgpu_cgroup_region_name() - Build the dmem cgroup region name for an amdgpu.
+ * @fd: amdgpu device fd.
+ *
+ * Constructs the full dmem cgroup region path for VRAM on the device
+ * identified by @fd.  The returned string has the form
+ * ``drm/<pci-slot>/vram`` (e.g. ``drm/0000:03:00.0/vram``), matching
+ * the name registered by the kernel driver via drmm_cgroup_register_region().
+ *
+ * Return: A newly allocated string that the caller must free(), or %NULL if
+ * @region is not tracked by the dmem cgroup controller.
+ */
+char *amdgpu_cgroup_region_name(int fd)
+{
+	char pci_slot[NAME_MAX];
+	char *name;
+
+	igt_device_get_pci_slot_name(fd, pci_slot);
+
+	igt_assert(asprintf(&name, "drm/%s/vram", pci_slot) > 0);
+	return name;
+}
+
 /**
  * Wait for specific value in memory with timeout
  */
diff --git a/lib/amdgpu/amd_memory.h b/lib/amdgpu/amd_memory.h
index e26c85bc4b0a..de169e580c1b 100644
--- a/lib/amdgpu/amd_memory.h
+++ b/lib/amdgpu/amd_memory.h
@@ -105,6 +105,8 @@ void
 bool
 virtual_free_memory(void *address, unsigned int size);
 
+char *amdgpu_cgroup_region_name(int fd);
+
 bool
 wait_on_value(unsigned int *ptr, unsigned int expected);
 #endif

-- 
2.47.3

[PATCH i-g-t v6 6/9] lib/amdgpu: add amdgpu support to igt_dmem_driver

[Thadeu Lima de Souza Cascardo]

This allows dmem cgroups tests to run on top of amdgpu driver, adding
support to allocate and release VRAM memory.

This does this by allocating a BO from VRAM domain, which will try to
place BOs on VRAM, but may fallback to GTT.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
---
 lib/amdgpu/amd_dmem.c | 90 +++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/igt_dmem_driver.h |  1 +
 lib/meson.build       |  1 +
 3 files changed, 92 insertions(+)

diff --git a/lib/amdgpu/amd_dmem.c b/lib/amdgpu/amd_dmem.c
new file mode 100644
index 000000000000..cb0fed4b870a
--- /dev/null
+++ b/lib/amdgpu/amd_dmem.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright 2026 Valve Corporation
+ * Authors:
+ *  Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
+ */
+
+#include <errno.h>
+
+#include "igt.h"
+#include "igt_cgroup.h"
+#include "igt_dmem_driver.h"
+#include "lib/amdgpu/amd_memory.h"
+
+struct amdgpu_dmem_ctx {
+	int fd;
+	amdgpu_device_handle device;
+};
+
+static int amdgpu_dmem_init(void **ctx, int fd)
+{
+	struct amdgpu_dmem_ctx *actx;
+	uint32_t major, minor;
+	int err;
+
+	actx = malloc(sizeof(*actx));
+	if (!actx)
+		return -ENOMEM;
+
+	err = amdgpu_device_initialize(fd, &major, &minor, &actx->device);
+	if (err)
+		goto out;
+
+	actx->fd = fd;
+
+	*ctx = actx;
+
+	return 0;
+
+out:
+	free(actx);
+
+	return err;
+}
+
+static void amdgpu_dmem_deinit(void *ctx)
+{
+	struct amdgpu_dmem_ctx *actx = ctx;
+
+	amdgpu_device_deinitialize(actx->device);
+	free(actx);
+}
+
+static char * amdgpu_dmem_get_region_name(void *ctx)
+{
+	struct amdgpu_dmem_ctx *actx = ctx;
+
+	return amdgpu_cgroup_region_name(actx->fd);
+}
+
+static int amdgpu_dmem_allocate_vram(void *ctx, size_t len, void **ret_handle)
+{
+	struct amdgpu_dmem_ctx *actx = ctx;
+	amdgpu_bo_handle handle;
+	int err;
+
+	err = amdgpu_bo_alloc_wrap(actx->device, len, 4096,
+				   AMDGPU_GEM_DOMAIN_VRAM, 0, &handle);
+	if (err)
+		return err;
+
+	if (ret_handle)
+		*ret_handle = (void *) handle;
+
+	return 0;
+}
+
+static void amdgpu_dmem_free_vram(void *ctx, void *handle)
+{
+	amdgpu_bo_free(handle);
+}
+
+const struct igt_dmem_driver amdgpu_dmem_driver = {
+	.name = "amdgpu",
+	.get_region_name = amdgpu_dmem_get_region_name,
+	.init = amdgpu_dmem_init,
+	.deinit = amdgpu_dmem_deinit,
+	.allocate_vram = amdgpu_dmem_allocate_vram,
+	.free_vram = amdgpu_dmem_free_vram,
+};
diff --git a/lib/igt_dmem_driver.h b/lib/igt_dmem_driver.h
index e6998387eff9..f2d9d74196db 100644
--- a/lib/igt_dmem_driver.h
+++ b/lib/igt_dmem_driver.h
@@ -30,5 +30,6 @@ struct igt_dmem_driver {
 };
 
 extern const struct igt_dmem_driver xe_dmem_driver;
+extern const struct igt_dmem_driver amdgpu_dmem_driver;
 
 #endif
diff --git a/lib/meson.build b/lib/meson.build
index 022408ce6864..e191793f0097 100644
--- a/lib/meson.build
+++ b/lib/meson.build
@@ -205,6 +205,7 @@ if libdrm_amdgpu.found()
 		'amdgpu/amd_mmd_shared.c',
 		'amdgpu/amd_jpeg_shared.c',
 		'amdgpu/amd_utils.c',
+		'amdgpu/amd_dmem.c',
 		'amdgpu/amd_vcn_shared.c'
 	]
 	if libdrm_amdgpu.version().version_compare('> 2.4.99')

-- 
2.47.3

[PATCH i-g-t v6 7/9] tests/cgroup_dmem: add test for dmem.current

[Thadeu Lima de Souza Cascardo]

Based on the work of Thomas Hellström to test dmem.max eviction, add a
test for dmem.current usage after allocations and setting dmem.max.

Create a dmem cgroup, allocate close to capacity (or at most 4GiB),
check current usage is within a small slack of the expected allocation.
Then, set max to a small value and check allocations and current usage
are limited to the max set.  Set max to less than a single BO size, then
check no allocations are allowed and current usage is also within the
slack. After each allocation, release memory and check current usage
has gone down.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
---
 tests/cgroup_dmem.c | 262 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 257 insertions(+), 5 deletions(-)

diff --git a/tests/cgroup_dmem.c b/tests/cgroup_dmem.c
index 442c965f9bbf..ba5e6a2e3deb 100644
--- a/tests/cgroup_dmem.c
+++ b/tests/cgroup_dmem.c
@@ -1,6 +1,8 @@
 // SPDX-License-Identifier: MIT
 /*
  * Copyright © 2025 Intel Corporation
+ * Copyright © 2026 Intel Corporation
+ * Copyright 2026 Valve Corporation
  */
 
 /**
@@ -17,10 +19,217 @@
  * Test category: uapi
  */
 
+#include <errno.h>
 #include <inttypes.h>
+#include <signal.h>
+#include <stdatomic.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
 
+#include "drmtest.h"
 #include "igt.h"
+#include "igt_aux.h"
 #include "igt_cgroup.h"
+#include "igt_dmem_driver.h"
+
+#define BO_SIZE			SZ_64M
+#define MAX_LIMIT		((uint64_t)4 * SZ_1G)
+#define USAGE_POLL_MS		10
+#define USAGE_DROP_TIMEOUT_MS	1000
+
+/**
+ * SUBTEST: simple
+ * DESCRIPTION:
+ *  Creates a cgroup, moves the process into it, enumerates all dmem regions,
+ *  prints their capacity, system-wide current usage, per-cgroup current usage
+ *  and configured limits, then destroys the cgroup.
+ */
+
+/**
+ * SUBTEST: current
+ * DESCRIPTION:
+ *  Create a dmem cgroup, allocate close to capacity (or at most 4GiB),
+ *  check current usage is within a small slack of the expected allocation.
+ *  Then, set max to a small value and check allocations and current usage
+ *  are limited to the max set.
+ *  Set max to less than a single BO size, then check no allocations are allowed
+ *  and current usage is also within the slack.
+ *  After each allocation, release memory and check current usage has gone
+ *  down.
+ * REQUIREMENTS: xe or amdgpu device with at least one VRAM region
+ */
+
+static uint64_t wait_for_usage_drop(struct igt_cgroup *cg, const char *region,
+				    uint64_t limit)
+{
+	uint64_t current;
+	unsigned int elapsed = 0;
+
+	do {
+		igt_cgroup_dmem_get_current(cg, region, &current);
+		if (current <= limit)
+			return current;
+		usleep(USAGE_POLL_MS * 1000);
+		elapsed += USAGE_POLL_MS;
+	} while (elapsed < USAGE_DROP_TIMEOUT_MS);
+
+	return current;
+}
+
+static int allocate_vram(void **handles, const struct igt_dmem_driver *drv,
+			 void *ctx, int max_bo, size_t len)
+{
+	int i, err = 0;
+	for (i = 0; i < max_bo; i++) {
+		err = drv->allocate_vram(ctx, len, &handles[i]);
+		if (err)
+			break;
+	}
+	/* These are expected failures we can ignore. */
+	if (err == -ENOMEM || err == -ENOSPC)
+		err = 0;
+	if (!err)
+		return i;
+	for (i--; i >= 0; i--)
+		drv->free_vram(ctx, handles[i]);
+	return err;
+}
+
+static void free_vram(void **handles, const struct igt_dmem_driver *drv,
+		      void *ctx, int max_bo)
+{
+	int i;
+	for (i = 0; i < max_bo; i++)
+		drv->free_vram(ctx, handles[i]);
+}
+
+static void test_current(int fd, char *cg_region, unsigned int flags, const struct igt_dmem_driver *drv, void *ctx)
+{
+	struct igt_cgroup *cg;
+	void **handles;
+	uint64_t current, capacity, cg_max;
+	int n_bo = 0, max_bo;
+
+	igt_cgroup_dmem_get_capacity(cg_region, &capacity);
+	igt_require_f(capacity >= 4 * BO_SIZE,
+		      "VRAM capacity (%"PRIu64" MiB) too small to test\n",
+		      capacity / SZ_1M);
+
+	/*
+	 * Use up to 4 GiB, or the full capacity if the device has less.
+	 * Leave one BO_SIZE worth of headroom so the device isn't completely
+	 * exhausted before the cgroup limit is hit.
+	 */
+	cg_max = min(MAX_LIMIT, capacity - BO_SIZE);
+	cg_max = ALIGN_DOWN(cg_max, BO_SIZE);
+
+	/* Create cgroup and move into it */
+	cg = igt_cgroup_new("igt_cgroups_test");
+	igt_cgroup_move_current(cg);
+
+	max_bo = cg_max / BO_SIZE;
+
+	handles = calloc(max_bo, sizeof(handles[0]));
+	igt_assert_f(handles, "failed to allocate handles array");
+
+	n_bo = allocate_vram(handles, drv, ctx, max_bo, BO_SIZE);
+	igt_assert_f(n_bo > 0, "failed to allocate VRAM\n");
+
+	igt_cgroup_dmem_get_current(cg, cg_region, &current);
+	igt_debug("After fill: cgroup current = %"PRIu64" MiB, "
+		  "max = %"PRIu64" MiB\n",
+		  current / SZ_1M, cg_max / SZ_1M);
+	igt_assert_f(current == cg_max,
+		     "current usage (%"PRIu64" MiB) is not requested allocation (%"PRIu64" MiB)\n",
+		     current / SZ_1M, cg_max / SZ_1M);
+
+	free_vram(handles, drv, ctx, n_bo);
+	wait_for_usage_drop(cg, cg_region, 0);
+
+	igt_cgroup_dmem_get_current(cg, cg_region, &current);
+	igt_debug("After free: cgroup current = %"PRIu64" MiB, "
+		  "max = %"PRIu64" MiB\n",
+		  current / SZ_1M, cg_max / SZ_1M);
+	igt_assert_f(current == 0,
+		     "current usage (%"PRIu64" MiB) is not zero\n",
+		     current / SZ_1M);
+
+	/* Allow for a slack as there might be some extra pages allocated. */
+	igt_cgroup_dmem_set_max(cg, cg_region, 2 * BO_SIZE, false);
+
+	n_bo = allocate_vram(handles, drv, ctx, max_bo, BO_SIZE);
+	igt_assert_f(n_bo > 0, "failed to allocate VRAM\n");
+
+	igt_cgroup_dmem_get_current(cg, cg_region, &current);
+	igt_debug("After fill: cgroup current = %"PRIu64" MiB, "
+		  "max = %"PRIu64" MiB\n",
+		  current / SZ_1M, cg_max / SZ_1M);
+	igt_assert_f(current == 2 * BO_SIZE,
+		     "current usage (%"PRIu64" MiB) is not requested max allocation (%"PRIu64" MiB)\n",
+		     current / SZ_1M, cg_max / SZ_1M);
+
+	free_vram(handles, drv, ctx, n_bo);
+	wait_for_usage_drop(cg, cg_region, 0);
+
+	igt_cgroup_dmem_get_current(cg, cg_region, &current);
+	igt_debug("After free: cgroup current = %"PRIu64" MiB, "
+		  "max = %"PRIu64" MiB\n",
+		  current / SZ_1M, cg_max / SZ_1M);
+	igt_assert_f(current == 0,
+		     "current usage (%"PRIu64" MiB) is not zero\n",
+		     current / SZ_1M);
+
+	igt_cgroup_dmem_set_max(cg, cg_region, 0, false);
+
+	n_bo = allocate_vram(handles, drv, ctx, max_bo, BO_SIZE);
+
+	/*
+	 * amdgpu may succeed the allocation, by falling back to GTT, so no assertion here.
+	 * Verify by reading current usage.
+	 */
+
+	igt_cgroup_dmem_get_current(cg, cg_region, &current);
+	igt_debug("After fill: cgroup current = %"PRIu64" MiB, "
+		  "max = %"PRIu64" MiB\n",
+		  current / SZ_1M, cg_max / SZ_1M);
+	igt_assert_f(current == 0,
+		     "current usage (%"PRIu64" MiB) is not zero\n",
+		     current / SZ_1M);
+
+	if (n_bo > 0)
+		free_vram(handles, drv, ctx, n_bo);
+	wait_for_usage_drop(cg, cg_region, 0);
+
+	igt_cgroup_dmem_get_current(cg, cg_region, &current);
+	igt_debug("After free: cgroup current = %"PRIu64" MiB, "
+		  "max = %"PRIu64" MiB\n",
+		  current / SZ_1M, cg_max / SZ_1M);
+	igt_assert_f(current == 0,
+		     "current usage (%"PRIu64" MiB) is not zero\n",
+		     current / SZ_1M);
+
+	igt_cgroup_free(cg);
+}
+
+static const struct {
+	const char *name;
+	void (*test_fn)(int fd, char *cg_region, unsigned int flags, const struct igt_dmem_driver *drv, void *ctx);
+	unsigned int flags;
+} subtests[] = {
+	{ "current", test_current, 0 },
+	{ }
+};
+
+static const struct {
+	int driver_flag;
+	const struct igt_dmem_driver *driver;
+} drivers[] = {
+	{ DRIVER_XE, &xe_dmem_driver },
+	{ DRIVER_AMDGPU, &amdgpu_dmem_driver },
+	{ },
+};
 
 IGT_TEST_DESCRIPTION("Exercises the cgroup v2 dmem controller interface.");
 
@@ -32,7 +241,7 @@ static void fmt_bytes(uint64_t v, char *buf, size_t len)
 		snprintf(buf, len, "%" PRIu64, v);
 }
 
-int igt_simple_main()
+static void simple_cgroup(void)
 {
 	struct igt_cgroup *cg;
 	const char *region;
@@ -42,10 +251,6 @@ int igt_simple_main()
 	char min_s[32], low_s[32], max_s[32];
 	int i;
 
-	igt_require_f(igt_cgroup_dmem_available(),
-		      "No dmem regions found; is cgroup v2 with the "
-		      "dmem controller available?\n");
-
 	cg = igt_cgroup_new("igt-cgroup-dmem-test");
 	igt_assert_f(cg, "Failed to create cgroup\n");
 
@@ -90,3 +295,50 @@ int igt_simple_main()
 	igt_cgroup_dmem_regions_free(regions);
 	igt_cgroup_free(cg);
 }
+
+int igt_main()
+{
+	igt_fixture() {
+		igt_require_f(getuid() == 0, "Test requires root\n");
+		/* Check dmem cgroup controller is available before doing anything else */
+		igt_require_f(igt_cgroup_dmem_available(),
+			      "dmem cgroup controller not available (no cgroup v2 or no registered regions)\n");
+
+	}
+
+	igt_subtest("simple")
+		simple_cgroup();
+
+	for (int d = 0; drivers[d].driver; d++) {
+		igt_subtest_group() {
+			int fd = -1;
+			int ret = -1;
+			char *cg_region = NULL;
+			void *ctx = NULL;
+			igt_fixture() {
+				fd = drm_open_driver(drivers[d].driver_flag);
+				igt_require_f(fd >= 0,
+					"No %s device found, skipping\n",
+					drivers[d].driver->name);
+				ret = drivers[d].driver->init(&ctx, fd);
+				igt_require_f(ret == 0,
+					"Failed to initialize %s device, skipping\n",
+					drivers[d].driver->name);
+				cg_region = drivers[d].driver->get_region_name(ctx);
+				igt_require_f(cg_region, "Region not tracked by dmem cgroup controller\n");
+			}
+
+			for (int i = 0; subtests[i].name; i++)
+				igt_subtest_f("%s-%s", drivers[d].driver->name, subtests[i].name)
+					subtests[i].test_fn(fd, cg_region, subtests[i].flags, drivers[d].driver, ctx);
+
+			igt_fixture() {
+				if (!ret)
+					drivers[d].driver->deinit(ctx);
+				if (fd >= 0)
+					drm_close_driver(fd);
+				free(cg_region);
+			}
+		}
+	}
+}

-- 
2.47.3

[PATCH i-g-t v6 8/9] tests/cgroup_dmem: add dmem cgroup eviction test

[Thadeu Lima de Souza Cascardo]

From: Thomas Hellström <thomas.hellstrom@linux.intel.com>

The write_eviction subtest:
 - Creates a sub-cgroup and moves the test process into it.
 - Sets a dmem.max limit on the first VRAM region (up to 4 GiB, or
   the full capacity if smaller).
- Fills VRAM by repeatedly creating BOs placed in VRAM, depending on card
  support.
 - Verifies that cgroup current usage is within the expected range when
   the limit is hit.
 - Lowers dmem.max in 128 MiB steps, waiting for usage to follow each
   reduction.

The write_eviction_interruptible subtest runs the same test with
SIGCONT signals injected via igt_fork_signal_helper() and reports the
number of signals received.  When a signal interrupts kernel-side
eviction, a small BO allocation is used to re-trigger it.

Assisted-by: GitHub Copilot:claude-sonnet-4.6
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
---
 tests/cgroup_dmem.c | 149 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 149 insertions(+)

diff --git a/tests/cgroup_dmem.c b/tests/cgroup_dmem.c
index ba5e6a2e3deb..0d3b415acd54 100644
--- a/tests/cgroup_dmem.c
+++ b/tests/cgroup_dmem.c
@@ -36,9 +36,12 @@
 
 #define BO_SIZE			SZ_64M
 #define MAX_LIMIT		((uint64_t)4 * SZ_1G)
+#define EVICT_STEP		SZ_128M
 #define USAGE_POLL_MS		10
 #define USAGE_DROP_TIMEOUT_MS	1000
 
+#define TEST_INTERRUPTIBLE	(1 << 0)
+
 /**
  * SUBTEST: simple
  * DESCRIPTION:
@@ -61,6 +64,62 @@
  * REQUIREMENTS: xe or amdgpu device with at least one VRAM region
  */
 
+/**
+ * SUBTEST: write_eviction
+ * DESCRIPTION:
+ *   Create a dmem cgroup, move the current process into it and set the max
+ *   device memory limit for the first VRAM region to 4 GiB.  Then fill VRAM
+ *   by creating BOs with %DRM_XE_GEM_CREATE_FLAG_DEFER_BACKING (so that the
+ *   physical allocation is deferred until VM_BIND) and binding them into an
+ *   LR VM until the cgroup limit is hit.  Verify that the reported cgroup
+ *   current usage is within the expected range when the error occurs.
+ *   Finally lower the max limit in 256 MiB steps and verify that the cgroup
+ *   usage follows.
+ * REQUIREMENTS: must run as root; xe device with at least one VRAM region
+ */
+
+/**
+ * SUBTEST: write_eviction_interruptible
+ * DESCRIPTION:
+ *   Same as write_eviction but with SIGCONT signals injected throughout via
+ *   igt_fork_signal_helper() to verify that the dmem.max write path handles
+ *   signal interruption correctly.  A signal handler counts received signals
+ *   and the count is reported as debug output at the end of the test.
+ *   A signal interrupts the set-time eviction, and further eviction can be
+ *   triggered by an explicit allocation.
+ * REQUIREMENTS: must run as root; xe device with at least one VRAM region
+ */
+
+static atomic_int signal_count;
+static struct sigaction sigcont_oldact;
+
+static void sigcont_handler(int sig)
+{
+	atomic_fetch_add(&signal_count, 1);
+
+	/* Chain to the previous handler (IGT's dummy sig_handler) */
+	if (sigcont_oldact.sa_handler &&
+	    sigcont_oldact.sa_handler != SIG_IGN &&
+	    sigcont_oldact.sa_handler != SIG_DFL)
+		sigcont_oldact.sa_handler(sig);
+}
+
+static void install_sigcont_counter(void)
+{
+	struct sigaction sa;
+
+	atomic_store(&signal_count, 0);
+	igt_fork_signal_helper();
+	/*
+	 * Install the counter after igt_fork_signal_helper() so our handler
+	 * is not overwritten.  Save the old handler so we can chain to it.
+	 */
+	memset(&sa, 0, sizeof(sa));
+	sa.sa_handler = sigcont_handler;
+	sigemptyset(&sa.sa_mask);
+	sigaction(SIGCONT, &sa, &sigcont_oldact);
+}
+
 static uint64_t wait_for_usage_drop(struct igt_cgroup *cg, const char *region,
 				    uint64_t limit)
 {
@@ -213,12 +272,102 @@ static void test_current(int fd, char *cg_region, unsigned int flags, const stru
 	igt_cgroup_free(cg);
 }
 
+static void test_write_eviction(int fd, char *cg_region, unsigned int flags, const struct igt_dmem_driver *drv, void *ctx)
+{
+	struct igt_cgroup *cg;
+	void **handles;
+	int max_bo;
+	uint64_t current, capacity, cg_max, limit, after;
+	int err;
+
+	igt_cgroup_dmem_get_capacity(cg_region, &capacity);
+	igt_require_f(capacity >= 4 * BO_SIZE,
+		      "VRAM capacity (%"PRIu64" MiB) too small to test\n",
+		      capacity / SZ_1M);
+
+	/*
+	 * Use up to 4 GiB, or the full capacity if the device has less.
+	 * Leave one BO_SIZE worth of headroom so the device isn't completely
+	 * exhausted before the cgroup limit is hit.
+	 */
+	cg_max = min(MAX_LIMIT, capacity - BO_SIZE);
+	cg_max = ALIGN_DOWN(cg_max, EVICT_STEP);
+
+	if (flags & TEST_INTERRUPTIBLE)
+		install_sigcont_counter();
+
+	/* Create cgroup and move into it */
+	cg = igt_cgroup_new("igt_cgroups_test");
+	igt_cgroup_move_current(cg);
+	igt_cgroup_dmem_set_max(cg, cg_region, cg_max, false);
+
+	max_bo = (cg_max / BO_SIZE) + 8; /* headroom for overcommit */
+
+	handles = calloc(max_bo, sizeof(handles[0]));
+	igt_assert_f(handles, "failed to allocate handles array");
+
+	allocate_vram(handles, drv, ctx, max_bo, BO_SIZE);
+
+	igt_cgroup_dmem_get_current(cg, cg_region, &current);
+	igt_debug("After fill: cgroup current = %"PRIu64" MiB, "
+		  "max = %"PRIu64" MiB\n",
+		  current / SZ_1M, cg_max / SZ_1M);
+
+	igt_assert_f(current <= cg_max,
+		     "Usage %"PRIu64" MiB exceeds max %"PRIu64" MiB + slack\n",
+		     current / SZ_1M, cg_max / SZ_1M);
+
+	/* Phase 2: lower max in 256 MiB steps, verify usage follows */
+	limit = cg_max;
+	while (limit >= EVICT_STEP) {
+
+		limit -= EVICT_STEP;
+		igt_cgroup_dmem_set_max(cg, cg_region, limit, false);
+
+		igt_cgroup_dmem_get_current(cg, cg_region, &after);
+		igt_debug("Lowered max to %"PRIu64" MiB: usage = %"PRIu64" MiB\n",
+			  limit / SZ_1M, after / SZ_1M);
+
+		if (limit > EVICT_STEP) {
+			if ((flags & TEST_INTERRUPTIBLE) && after > limit) {
+				/* Let a new bo creation trigger eviction. */
+				void *handle;
+				err = drv->allocate_vram(ctx, BO_SIZE / 8, &handle);
+				igt_assert_f(err == 0,
+					"Error trying to allocate more VRAM to trigger eviction.");
+				drv->free_vram(ctx, handle);
+
+				igt_cgroup_dmem_get_current(cg, cg_region, &after);
+				igt_debug("Forced eviction max is %"PRIu64
+					  " MiB: usage = %"PRIu64" MiB\n",
+					  limit / SZ_1M, after / SZ_1M);
+			}
+
+			igt_assert_f(after <= limit,
+				     "Usage %"PRIu64" MiB did not follow max %"PRIu64" MiB\n",
+				     after / SZ_1M, limit / SZ_1M);
+		}
+	}
+
+	if (flags & TEST_INTERRUPTIBLE) {
+		igt_stop_signal_helper();
+		igt_info("Signals received during test: %d\n",
+			 atomic_load(&signal_count));
+	}
+
+	/* Cleanup */
+	igt_cgroup_dmem_set_max(cg, cg_region, IGT_CGROUP_DMEM_MAX, false);
+	igt_cgroup_free(cg);
+}
+
 static const struct {
 	const char *name;
 	void (*test_fn)(int fd, char *cg_region, unsigned int flags, const struct igt_dmem_driver *drv, void *ctx);
 	unsigned int flags;
 } subtests[] = {
 	{ "current", test_current, 0 },
+	{ "write_eviction", test_write_eviction, 0 },
+	{ "write_eviction_interruptible", test_write_eviction, TEST_INTERRUPTIBLE },
 	{ }
 };
 

-- 
2.47.3

[PATCH i-g-t v6 9/9] tests/cgroup_dmem: add write_eviction_nonblock subtest

[Thadeu Lima de Souza Cascardo]

From: Thomas Hellström <thomas.hellstrom@linux.intel.com>

Add write_eviction_nonblock to exercise the O_NONBLOCK path of the dmem
cgroup max interface.  After filling VRAM to the cgroup limit, each
limit-lowering step writes dmem.max with O_NONBLOCK so that synchronous
eviction is skipped.  The test then verifies that usage has not yet
dropped below the new limit, allocates a small BO to trigger eviction
explicitly, and finally confirms that usage falls within bounds.

Assisted-by: GitHub Copilot:claude-sonnet-4.6
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
---
 tests/cgroup_dmem.c | 37 ++++++++++++++++++++++++++++++++++---
 1 file changed, 34 insertions(+), 3 deletions(-)

diff --git a/tests/cgroup_dmem.c b/tests/cgroup_dmem.c
index 0d3b415acd54..ee6345c17878 100644
--- a/tests/cgroup_dmem.c
+++ b/tests/cgroup_dmem.c
@@ -41,6 +41,7 @@
 #define USAGE_DROP_TIMEOUT_MS	1000
 
 #define TEST_INTERRUPTIBLE	(1 << 0)
+#define TEST_NONBLOCK		(1 << 1)
 
 /**
  * SUBTEST: simple
@@ -90,6 +91,18 @@
  * REQUIREMENTS: must run as root; xe device with at least one VRAM region
  */
 
+/**
+ * SUBTEST: write_eviction_nonblock
+ * DESCRIPTION:
+ *   Same fill phase as write_eviction.  In the limit-lowering phase dmem.max
+ *   is written with O_NONBLOCK, which causes the kernel to skip synchronous
+ *   eviction.  After each nonblock write the test verifies that usage has not
+ *   yet dropped below the new limit, then triggers eviction explicitly by
+ *   allocating a small BO.  Finally verifies that usage falls within bounds
+ *   after the forced eviction.
+ * REQUIREMENTS: must run as root; xe device with at least one VRAM region
+ */
+
 static atomic_int signal_count;
 static struct sigaction sigcont_oldact;
 
@@ -277,7 +290,7 @@ static void test_write_eviction(int fd, char *cg_region, unsigned int flags, con
 	struct igt_cgroup *cg;
 	void **handles;
 	int max_bo;
-	uint64_t current, capacity, cg_max, limit, after;
+	uint64_t current, capacity, cg_max, limit, after, before;
 	int err;
 
 	igt_cgroup_dmem_get_capacity(cg_region, &capacity);
@@ -322,14 +335,31 @@ static void test_write_eviction(int fd, char *cg_region, unsigned int flags, con
 	while (limit >= EVICT_STEP) {
 
 		limit -= EVICT_STEP;
-		igt_cgroup_dmem_set_max(cg, cg_region, limit, false);
+
+		if (flags & TEST_NONBLOCK)
+			igt_cgroup_dmem_get_current(cg, cg_region, &before);
+
+		igt_cgroup_dmem_set_max(cg, cg_region, limit,
+					!!(flags & TEST_NONBLOCK));
 
 		igt_cgroup_dmem_get_current(cg, cg_region, &after);
 		igt_debug("Lowered max to %"PRIu64" MiB: usage = %"PRIu64" MiB\n",
 			  limit / SZ_1M, after / SZ_1M);
 
+		if (flags & TEST_NONBLOCK) {
+			/*
+			 * O_NONBLOCK skips eviction: verify usage has not
+			 * dropped below the new limit yet.
+			 */
+			igt_assert_f(after == before,
+				     "Expected no eviction with O_NONBLOCK, but "
+				     "usage dropped from %"PRIu64" MiB to %"PRIu64" MiB "
+				     "(limit %"PRIu64" MiB)\n",
+				     before / SZ_1M, after / SZ_1M, limit / SZ_1M);
+		}
+
 		if (limit > EVICT_STEP) {
-			if ((flags & TEST_INTERRUPTIBLE) && after > limit) {
+			if ((flags & (TEST_INTERRUPTIBLE | TEST_NONBLOCK)) && after > limit) {
 				/* Let a new bo creation trigger eviction. */
 				void *handle;
 				err = drv->allocate_vram(ctx, BO_SIZE / 8, &handle);
@@ -368,6 +398,7 @@ static const struct {
 	{ "current", test_current, 0 },
 	{ "write_eviction", test_write_eviction, 0 },
 	{ "write_eviction_interruptible", test_write_eviction, TEST_INTERRUPTIBLE },
+	{ "write_eviction_nonblock", test_write_eviction, TEST_NONBLOCK },
 	{ }
 };
 

-- 
2.47.3

Re: [PATCH i-g-t v6 5/9] lib/amdgpu: add amdgpu_cgroup_region_name

[Tvrtko Ursulin]

On 03/09/2026 23:00, Thadeu Lima de Souza Cascardo wrote:
> The amdgpu dmem region name uses its PCI address, just like the one from
> Xe, but there is only a single VRAM region.
> 
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
> ---
>   lib/amdgpu/amd_memory.c | 25 +++++++++++++++++++++++++
>   lib/amdgpu/amd_memory.h |  2 ++
>   2 files changed, 27 insertions(+)
> 
> diff --git a/lib/amdgpu/amd_memory.c b/lib/amdgpu/amd_memory.c
> index 12fe23c65ab2..2da4a8a4baee 100644
> --- a/lib/amdgpu/amd_memory.c
> +++ b/lib/amdgpu/amd_memory.c
> @@ -30,9 +30,11 @@
>   #include <amdgpu_drm.h>
>   #include <stdio.h>
>   #include <string.h>
> +#include <limits.h>
>   #include <unistd.h>
>   #include <sys/mman.h>
>   #include <inttypes.h>
> +#include "igt_device.h"
>   
>   /**
>    *
> @@ -679,6 +681,29 @@ bool virtual_free_memory(void *address, unsigned int size)
>   	}
>   }
>   
> +/**
> + * amdgpu_cgroup_region_name() - Build the dmem cgroup region name for an amdgpu.
> + * @fd: amdgpu device fd.
> + *
> + * Constructs the full dmem cgroup region path for VRAM on the device
> + * identified by @fd.  The returned string has the form
> + * ``drm/<pci-slot>/vram`` (e.g. ``drm/0000:03:00.0/vram``), matching
> + * the name registered by the kernel driver via drmm_cgroup_register_region().
> + *
> + * Return: A newly allocated string that the caller must free(), or %NULL if
> + * @region is not tracked by the dmem cgroup controller.
> + */
> +char *amdgpu_cgroup_region_name(int fd)
> +{
> +	char pci_slot[NAME_MAX];
> +	char *name;
> +
> +	igt_device_get_pci_slot_name(fd, pci_slot);
> +
> +	igt_assert(asprintf(&name, "drm/%s/vram", pci_slot) > 0);
> +	return name;
> +}
> +
>   /**
>    * Wait for specific value in memory with timeout
>    */
> diff --git a/lib/amdgpu/amd_memory.h b/lib/amdgpu/amd_memory.h
> index e26c85bc4b0a..de169e580c1b 100644
> --- a/lib/amdgpu/amd_memory.h
> +++ b/lib/amdgpu/amd_memory.h
> @@ -105,6 +105,8 @@ void
>   bool
>   virtual_free_memory(void *address, unsigned int size);
>   
> +char *amdgpu_cgroup_region_name(int fd);
> +
>   bool
>   wait_on_value(unsigned int *ptr, unsigned int expected);
>   #endif
> 

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>

Regards,

Tvrtko

Re: [PATCH i-g-t v6 4/9] lib/xe: Introduce dmem driver and implement Xe support

[Tvrtko Ursulin]

On 03/09/2026 23:00, Thadeu Lima de Souza Cascardo wrote:
> In order to be reuse the same dmem tests with multiple drivers, we need to
> abstract a few operations. That includes getting the region name, and
> allocating and releasing VRAM. As there is some initialization also when
> multiple allocations are done, also provide init and deinit functions.
> 
> The Xe implementation was based on the original operations from
> xe_cgroups.c written by Thomas Hellström. However, instead of doing a
> deferred backing, followed by a bind, it does a simple non-deferred GEM
> object creation on the VRAM region.
> 
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
> ---
>   lib/igt_dmem_driver.h | 34 ++++++++++++++++++
>   lib/meson.build       |  1 +
>   lib/xe/xe_dmem.c      | 97 +++++++++++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 132 insertions(+)
> 
> diff --git a/lib/igt_dmem_driver.h b/lib/igt_dmem_driver.h
> new file mode 100644
> index 000000000000..e6998387eff9
> --- /dev/null
> +++ b/lib/igt_dmem_driver.h
> @@ -0,0 +1,34 @@
> +// SPDX-License-Identifier: MIT
> +/*
> + * Copyright 2026 Valve Corporation
> + * Authors:
> + *  Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
> + */
> +
> +#ifndef __IGT_DMEM_DRIVER_H__
> +#define __IGT_DMEM_DRIVER_H__
> +
> +#include <stdlib.h>
> +
> +/**
> + * struct igt_dmem_driver - vendor driver to allocate and free device memory
> + *
> + */
> +struct igt_dmem_driver {
> +	/** @name: Driver name */
> +	const char *name;
> +	/** @init: Initialize an opaque context given a DRM device fd */
> +	int (*init)(void **ctx, int fd);
> +	/** @deinit: Release resources associated with context */
> +	void (*deinit)(void *ctx);
> +	/** @get_region_name: Return expected region name at dmem cgroup files */
> +	char * (*get_region_name)(void *ctx);

Nit - mention it returns newly allocated memory caller must free?

But LGTM on the whole:

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>

Regards,

Tvrtko

> +	/** @allocate_vram: Allocate @len sized vram and return an opaque @handle */
> +	int (*allocate_vram)(void *ctx, size_t len, void **handle);
> +	/** @free_vram: Free vram associated with @handle */
> +	void (*free_vram)(void *ctx, void *handle);
> +};
> +
> +extern const struct igt_dmem_driver xe_dmem_driver;
> +
> +#endif
> diff --git a/lib/meson.build b/lib/meson.build
> index b7e1be61d844..022408ce6864 100644
> --- a/lib/meson.build
> +++ b/lib/meson.build
> @@ -130,6 +130,7 @@ lib_sources = [
>   	'igt_dsc.c',
>   	'igt_hook.c',
>   	'xe/xe_device.c',
> +	'xe/xe_dmem.c',
>   	'xe/xe_ggtt.c',
>   	'xe/xe_gt.c',
>   	'xe/xe_ioctl.c',
> diff --git a/lib/xe/xe_dmem.c b/lib/xe/xe_dmem.c
> new file mode 100644
> index 000000000000..628c905997d4
> --- /dev/null
> +++ b/lib/xe/xe_dmem.c
> @@ -0,0 +1,97 @@
> +// SPDX-License-Identifier: MIT
> +/*
> + * Copyright 2026 Valve Corporation
> + * Authors:
> + *  Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
> + */
> +
> +#include <errno.h>
> +
> +#include "igt.h"
> +#include "igt_cgroup.h"
> +#include "igt_dmem_driver.h"
> +#include "xe_drm.h"
> +#include "xe/xe_ioctl.h"
> +#include "xe/xe_query.h"
> +
> +struct xe_dmem_ctx {
> +	int fd;
> +	uint64_t vram_region;
> +};
> +
> +static int xe_dmem_init(void **ctx, int fd)
> +{
> +	struct xe_dmem_ctx *xe_ctx;
> +	uint64_t region;
> +
> +	xe_ctx = malloc(sizeof(*xe_ctx));
> +	if (!xe_ctx)
> +		return -ENOMEM;
> +
> +	xe_ctx->vram_region = 0;
> +	/* Find first VRAM region */
> +	xe_for_each_mem_region(fd, all_memory_regions(fd), region) {
> +		if (xe_region_class(fd, region) == DRM_XE_MEM_REGION_CLASS_VRAM) {
> +			xe_ctx->vram_region = region;
> +			break;
> +		}
> +	}
> +	if (!xe_ctx->vram_region)
> +		goto out;
> +
> +	xe_ctx->fd = fd;
> +
> +	*ctx = xe_ctx;
> +
> +	return 0;
> +
> +out:
> +	free(xe_ctx);
> +
> +	return -ENOMEM;
> +}
> +
> +static void xe_dmem_deinit(void *ctx)
> +{
> +	struct xe_dmem_ctx *xe_ctx = ctx;
> +
> +	free(xe_ctx);
> +}
> +
> +static char * xe_dmem_get_region_name(void *ctx)
> +{
> +	struct xe_dmem_ctx *xe_ctx = ctx;
> +
> +	return xe_cgroup_region_name(xe_ctx->fd, xe_ctx->vram_region);
> +}
> +
> +static int xe_dmem_allocate_vram(void *ctx, size_t len, void **ret_handle)
> +{
> +	struct xe_dmem_ctx *xe_ctx = ctx;
> +	uint32_t handle;
> +	int err;
> +
> +	err = __xe_bo_create(xe_ctx->fd, 0, len, xe_ctx->vram_region, 0,
> +			     NULL, &handle);
> +	if (err)
> +		return err;
> +
> +	*ret_handle = (void *)(uintptr_t) handle;
> +	return 0;
> +}
> +
> +static void xe_dmem_free_vram(void *ctx, void *handle)
> +{
> +	struct xe_dmem_ctx *xe_ctx = ctx;
> +
> +	gem_close(xe_ctx->fd, (uint32_t)(uintptr_t) handle);
> +}
> +
> +const struct igt_dmem_driver xe_dmem_driver = {
> +	.name = "xe",
> +	.get_region_name = xe_dmem_get_region_name,
> +	.init = xe_dmem_init,
> +	.deinit = xe_dmem_deinit,
> +	.allocate_vram = xe_dmem_allocate_vram,
> +	.free_vram = xe_dmem_free_vram,
> +};
> 

Re: [PATCH i-g-t v6 6/9] lib/amdgpu: add amdgpu support to igt_dmem_driver

[Tvrtko Ursulin]

On 03/09/2026 23:00, Thadeu Lima de Souza Cascardo wrote:
> This allows dmem cgroups tests to run on top of amdgpu driver, adding
> support to allocate and release VRAM memory.
> 
> This does this by allocating a BO from VRAM domain, which will try to
> place BOs on VRAM, but may fallback to GTT.
> 
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
> ---
>   lib/amdgpu/amd_dmem.c | 90 +++++++++++++++++++++++++++++++++++++++++++++++++++
>   lib/igt_dmem_driver.h |  1 +
>   lib/meson.build       |  1 +
>   3 files changed, 92 insertions(+)
> 
> diff --git a/lib/amdgpu/amd_dmem.c b/lib/amdgpu/amd_dmem.c
> new file mode 100644
> index 000000000000..cb0fed4b870a
> --- /dev/null
> +++ b/lib/amdgpu/amd_dmem.c
> @@ -0,0 +1,90 @@
> +// SPDX-License-Identifier: MIT
> +/*
> + * Copyright 2026 Valve Corporation
> + * Authors:
> + *  Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
> + */
> +
> +#include <errno.h>
> +
> +#include "igt.h"
> +#include "igt_cgroup.h"
> +#include "igt_dmem_driver.h"
> +#include "lib/amdgpu/amd_memory.h"
> +
> +struct amdgpu_dmem_ctx {
> +	int fd;
> +	amdgpu_device_handle device;
> +};
> +
> +static int amdgpu_dmem_init(void **ctx, int fd)
> +{
> +	struct amdgpu_dmem_ctx *actx;
> +	uint32_t major, minor;
> +	int err;
> +
> +	actx = malloc(sizeof(*actx));
> +	if (!actx)
> +		return -ENOMEM;
> +
> +	err = amdgpu_device_initialize(fd, &major, &minor, &actx->device);
> +	if (err)
> +		goto out;
> +
> +	actx->fd = fd;
> +
> +	*ctx = actx;
> +
> +	return 0;
> +
> +out:
> +	free(actx);
> +
> +	return err;
> +}
> +
> +static void amdgpu_dmem_deinit(void *ctx)
> +{
> +	struct amdgpu_dmem_ctx *actx = ctx;
> +
> +	amdgpu_device_deinitialize(actx->device);
> +	free(actx);
> +}
> +
> +static char * amdgpu_dmem_get_region_name(void *ctx)
> +{
> +	struct amdgpu_dmem_ctx *actx = ctx;
> +
> +	return amdgpu_cgroup_region_name(actx->fd);
> +}
> +
> +static int amdgpu_dmem_allocate_vram(void *ctx, size_t len, void **ret_handle)
> +{
> +	struct amdgpu_dmem_ctx *actx = ctx;
> +	amdgpu_bo_handle handle;
> +	int err;
> +
> +	err = amdgpu_bo_alloc_wrap(actx->device, len, 4096,
> +				   AMDGPU_GEM_DOMAIN_VRAM, 0, &handle);
> +	if (err)
> +		return err;
> +
> +	if (ret_handle)
> +		*ret_handle = (void *) handle;

Is there an use case for ret_handle == NULL? Xe backend does not bother 
with the check. This aside, the rest looks good to me:

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>

Regards,

Tvrtko

> +
> +	return 0;
> +}
> +
> +static void amdgpu_dmem_free_vram(void *ctx, void *handle)
> +{
> +	amdgpu_bo_free(handle);
> +}
> +
> +const struct igt_dmem_driver amdgpu_dmem_driver = {
> +	.name = "amdgpu",
> +	.get_region_name = amdgpu_dmem_get_region_name,
> +	.init = amdgpu_dmem_init,
> +	.deinit = amdgpu_dmem_deinit,
> +	.allocate_vram = amdgpu_dmem_allocate_vram,
> +	.free_vram = amdgpu_dmem_free_vram,
> +};
> diff --git a/lib/igt_dmem_driver.h b/lib/igt_dmem_driver.h
> index e6998387eff9..f2d9d74196db 100644
> --- a/lib/igt_dmem_driver.h
> +++ b/lib/igt_dmem_driver.h
> @@ -30,5 +30,6 @@ struct igt_dmem_driver {
>   };
>   
>   extern const struct igt_dmem_driver xe_dmem_driver;
> +extern const struct igt_dmem_driver amdgpu_dmem_driver;
>   
>   #endif
> diff --git a/lib/meson.build b/lib/meson.build
> index 022408ce6864..e191793f0097 100644
> --- a/lib/meson.build
> +++ b/lib/meson.build
> @@ -205,6 +205,7 @@ if libdrm_amdgpu.found()
>   		'amdgpu/amd_mmd_shared.c',
>   		'amdgpu/amd_jpeg_shared.c',
>   		'amdgpu/amd_utils.c',
> +		'amdgpu/amd_dmem.c',
>   		'amdgpu/amd_vcn_shared.c'
>   	]
>   	if libdrm_amdgpu.version().version_compare('> 2.4.99')
> 

Re: [PATCH i-g-t v6 7/9] tests/cgroup_dmem: add test for dmem.current

[Tvrtko Ursulin]

On 03/09/2026 23:00, Thadeu Lima de Souza Cascardo wrote:
> Based on the work of Thomas Hellström to test dmem.max eviction, add a
> test for dmem.current usage after allocations and setting dmem.max.
> 
> Create a dmem cgroup, allocate close to capacity (or at most 4GiB),
> check current usage is within a small slack of the expected allocation.
> Then, set max to a small value and check allocations and current usage
> are limited to the max set.  Set max to less than a single BO size, then
> check no allocations are allowed and current usage is also within the
> slack. After each allocation, release memory and check current usage
> has gone down.
> 
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
> ---
>   tests/cgroup_dmem.c | 262 +++++++++++++++++++++++++++++++++++++++++++++++++++-
>   1 file changed, 257 insertions(+), 5 deletions(-)
> 
> diff --git a/tests/cgroup_dmem.c b/tests/cgroup_dmem.c
> index 442c965f9bbf..ba5e6a2e3deb 100644
> --- a/tests/cgroup_dmem.c
> +++ b/tests/cgroup_dmem.c
> @@ -1,6 +1,8 @@
>   // SPDX-License-Identifier: MIT
>   /*
>    * Copyright © 2025 Intel Corporation
> + * Copyright © 2026 Intel Corporation

This is from a patch by Thomas? I would put a Co-developed-by: or his 
SoB even if that is agreeable since Intel's copyright is being recorded.

> + * Copyright 2026 Valve Corporation
>    */
>   
>   /**
> @@ -17,10 +19,217 @@
>    * Test category: uapi
>    */
>   
> +#include <errno.h>
>   #include <inttypes.h>
> +#include <signal.h>
> +#include <stdatomic.h>
> +#include <stdint.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <unistd.h>
>   
> +#include "drmtest.h"
>   #include "igt.h"
> +#include "igt_aux.h"
>   #include "igt_cgroup.h"
> +#include "igt_dmem_driver.h"
> +
> +#define BO_SIZE			SZ_64M
> +#define MAX_LIMIT		((uint64_t)4 * SZ_1G)
> +#define USAGE_POLL_MS		10
> +#define USAGE_DROP_TIMEOUT_MS	1000
> +
> +/**
> + * SUBTEST: simple
> + * DESCRIPTION:
> + *  Creates a cgroup, moves the process into it, enumerates all dmem regions,
> + *  prints their capacity, system-wide current usage, per-cgroup current usage
> + *  and configured limits, then destroys the cgroup.
> + */
> +
> +/**
> + * SUBTEST: current
> + * DESCRIPTION:
> + *  Create a dmem cgroup, allocate close to capacity (or at most 4GiB),
> + *  check current usage is within a small slack of the expected allocation.
> + *  Then, set max to a small value and check allocations and current usage
> + *  are limited to the max set.
> + *  Set max to less than a single BO size, then check no allocations are allowed
> + *  and current usage is also within the slack.
> + *  After each allocation, release memory and check current usage has gone
> + *  down.
> + * REQUIREMENTS: xe or amdgpu device with at least one VRAM region

I am out of touch the IGT documentation requirements but assuming the 
REQUIREMENTS: is real, I would suggest instead of "xe or amdgpu device" 
you put something like "a device supported by igt_dmem_driver.c" or 
something like that.

> + */
> +
> +static uint64_t wait_for_usage_drop(struct igt_cgroup *cg, const char *region,
> +				    uint64_t limit)
> +{
> +	uint64_t current;
> +	unsigned int elapsed = 0;
> +
> +	do {
> +		igt_cgroup_dmem_get_current(cg, region, &current);
> +		if (current <= limit)
> +			return current;
> +		usleep(USAGE_POLL_MS * 1000);
> +		elapsed += USAGE_POLL_MS;
> +	} while (elapsed < USAGE_DROP_TIMEOUT_MS);
> +
> +	return current;
> +}
> +
> +static int allocate_vram(void **handles, const struct igt_dmem_driver *drv,
> +			 void *ctx, int max_bo, size_t len)
> +{
> +	int i, err = 0;

Nit - blank lines between the declarations and bodies are a bit 
inconsistent in the patch.

> +	for (i = 0; i < max_bo; i++) {
> +		err = drv->allocate_vram(ctx, len, &handles[i]);
> +		if (err)
> +			break;
> +	}
> +	/* These are expected failures we can ignore. */
> +	if (err == -ENOMEM || err == -ENOSPC)
> +		err = 0;
> +	if (!err)
> +		return i;
> +	for (i--; i >= 0; i--)
> +		drv->free_vram(ctx, handles[i]);
> +	return err;
> +}
> +
> +static void free_vram(void **handles, const struct igt_dmem_driver *drv,
> +		      void *ctx, int max_bo)
> +{
> +	int i;
> +	for (i = 0; i < max_bo; i++)
> +		drv->free_vram(ctx, handles[i]);
> +}
> +
> +static void test_current(int fd, char *cg_region, unsigned int flags, const struct igt_dmem_driver *drv, void *ctx)
> +{
> +	struct igt_cgroup *cg;
> +	void **handles;
> +	uint64_t current, capacity, cg_max;
> +	int n_bo = 0, max_bo;
> +
> +	igt_cgroup_dmem_get_capacity(cg_region, &capacity);
> +	igt_require_f(capacity >= 4 * BO_SIZE,

4 * BO_SIZE = 256 Mib - is that what you intended?

> +		      "VRAM capacity (%"PRIu64" MiB) too small to test\n",
> +		      capacity / SZ_1M);
> +
> +	/*
> +	 * Use up to 4 GiB, or the full capacity if the device has less.
> +	 * Leave one BO_SIZE worth of headroom so the device isn't completely
> +	 * exhausted before the cgroup limit is hit.
> +	 */
> +	cg_max = min(MAX_LIMIT, capacity - BO_SIZE);
> +	cg_max = ALIGN_DOWN(cg_max, BO_SIZE);
> +
> +	/* Create cgroup and move into it */
> +	cg = igt_cgroup_new("igt_cgroups_test");

Looking at the igt_cgroup_new() implementation there isn't any automatic 
cleanup on failure registered, right? If so, then any test failure below 
will prevent further tests from running. At least for the Intel's 
automated CI that will be a problem but I let Intel people give their 
opinion on what should happen.

> +	igt_cgroup_move_current(cg);
> +
> +	max_bo = cg_max / BO_SIZE;
> +
> +	handles = calloc(max_bo, sizeof(handles[0]));

If clearing on alloc is required then it could be that clearing in 
free_vram() also is since the array is reused in the test? Or clearing 
is not needed at either end? What I am trying to say is that it looks 
both should be the same in this respect.

> +	igt_assert_f(handles, "failed to allocate handles array");
> +
> +	n_bo = allocate_vram(handles, drv, ctx, max_bo, BO_SIZE);
> +	igt_assert_f(n_bo > 0, "failed to allocate VRAM\n");
> +
> +	igt_cgroup_dmem_get_current(cg, cg_region, &current);
> +	igt_debug("After fill: cgroup current = %"PRIu64" MiB, "
> +		  "max = %"PRIu64" MiB\n",
> +		  current / SZ_1M, cg_max / SZ_1M);
> +	igt_assert_f(current == cg_max,
> +		     "current usage (%"PRIu64" MiB) is not requested allocation (%"PRIu64" MiB)\n",
> +		     current / SZ_1M, cg_max / SZ_1M);

Similar class of a problem as above - if the test fails here objects are 
not freed and because fd is shared subsquent tests will also fail, right?

On the assert itself, the strict equality may become a problem if driver 
internal objects start getting charger to the cgroup. I know there are 
plans underway to close that gap. So maybe it would be best to start 
with current >= cg_max.

> +
> +	free_vram(handles, drv, ctx, n_bo);
> +	wait_for_usage_drop(cg, cg_region, 0);

Similar as above - usage may not drop to zero all while the fd is open. 
I would make it robust by sampling a baseline at the start of the test 
and have the checks relative to it.

> +
> +	igt_cgroup_dmem_get_current(cg, cg_region, &current);
> +	igt_debug("After free: cgroup current = %"PRIu64" MiB, "
> +		  "max = %"PRIu64" MiB\n",
> +		  current / SZ_1M, cg_max / SZ_1M);
> +	igt_assert_f(current == 0,
> +		     "current usage (%"PRIu64" MiB) is not zero\n",
> +		     current / SZ_1M);
> +
> +	/* Allow for a slack as there might be some extra pages allocated. */
> +	igt_cgroup_dmem_set_max(cg, cg_region, 2 * BO_SIZE, false);

I did not get what is the slack? Max is set to 2 BOs and then below it 
is checked usage is exactly 2 BOs.

> +
> +	n_bo = allocate_vram(handles, drv, ctx, max_bo, BO_SIZE);
> +	igt_assert_f(n_bo > 0, "failed to allocate VRAM\n");
> +
> +	igt_cgroup_dmem_get_current(cg, cg_region, &current);
> +	igt_debug("After fill: cgroup current = %"PRIu64" MiB, "
> +		  "max = %"PRIu64" MiB\n",
> +		  current / SZ_1M, cg_max / SZ_1M);
> +	igt_assert_f(current == 2 * BO_SIZE,
> +		     "current usage (%"PRIu64" MiB) is not requested max allocation (%"PRIu64" MiB)\n",
> +		     current / SZ_1M, cg_max / SZ_1M);
> +
> +	free_vram(handles, drv, ctx, n_bo);
> +	wait_for_usage_drop(cg, cg_region, 0);
> +
> +	igt_cgroup_dmem_get_current(cg, cg_region, &current);
> +	igt_debug("After free: cgroup current = %"PRIu64" MiB, "
> +		  "max = %"PRIu64" MiB\n",
> +		  current / SZ_1M, cg_max / SZ_1M);
> +	igt_assert_f(current == 0,
> +		     "current usage (%"PRIu64" MiB) is not zero\n",
> +		     current / SZ_1M);
> +
> +	igt_cgroup_dmem_set_max(cg, cg_region, 0, false);
> +
> +	n_bo = allocate_vram(handles, drv, ctx, max_bo, BO_SIZE);
> +
> +	/*
> +	 * amdgpu may succeed the allocation, by falling back to GTT, so no assertion here.
> +	 * Verify by reading current usage.
> +	 */

On APUs or even discrete? Could you make the test explicitly control it 
and ask for no automatic fallback?

Ar at least pass drivers[].driver_flag so test can have stricter 
asserts. Even strcmp on drv->name could work.

Regards,

Tvrtko

> +
> +	igt_cgroup_dmem_get_current(cg, cg_region, &current);
> +	igt_debug("After fill: cgroup current = %"PRIu64" MiB, "
> +		  "max = %"PRIu64" MiB\n",
> +		  current / SZ_1M, cg_max / SZ_1M);
> +	igt_assert_f(current == 0,
> +		     "current usage (%"PRIu64" MiB) is not zero\n",
> +		     current / SZ_1M);
> +
> +	if (n_bo > 0)
> +		free_vram(handles, drv, ctx, n_bo);
> +	wait_for_usage_drop(cg, cg_region, 0);
> +
> +	igt_cgroup_dmem_get_current(cg, cg_region, &current);
> +	igt_debug("After free: cgroup current = %"PRIu64" MiB, "
> +		  "max = %"PRIu64" MiB\n",
> +		  current / SZ_1M, cg_max / SZ_1M);
> +	igt_assert_f(current == 0,
> +		     "current usage (%"PRIu64" MiB) is not zero\n",
> +		     current / SZ_1M);
> +
> +	igt_cgroup_free(cg);
> +}
> +
> +static const struct {
> +	const char *name;
> +	void (*test_fn)(int fd, char *cg_region, unsigned int flags, const struct igt_dmem_driver *drv, void *ctx);
> +	unsigned int flags;
> +} subtests[] = {
> +	{ "current", test_current, 0 },
> +	{ }
> +};
> +
> +static const struct {
> +	int driver_flag;
> +	const struct igt_dmem_driver *driver;
> +} drivers[] = {
> +	{ DRIVER_XE, &xe_dmem_driver },
> +	{ DRIVER_AMDGPU, &amdgpu_dmem_driver },
> +	{ },
> +};
>   
>   IGT_TEST_DESCRIPTION("Exercises the cgroup v2 dmem controller interface.");
>   
> @@ -32,7 +241,7 @@ static void fmt_bytes(uint64_t v, char *buf, size_t len)
>   		snprintf(buf, len, "%" PRIu64, v);
>   }
>   
> -int igt_simple_main()
> +static void simple_cgroup(void)
>   {
>   	struct igt_cgroup *cg;
>   	const char *region;
> @@ -42,10 +251,6 @@ int igt_simple_main()
>   	char min_s[32], low_s[32], max_s[32];
>   	int i;
>   
> -	igt_require_f(igt_cgroup_dmem_available(),
> -		      "No dmem regions found; is cgroup v2 with the "
> -		      "dmem controller available?\n");
> -
>   	cg = igt_cgroup_new("igt-cgroup-dmem-test");
>   	igt_assert_f(cg, "Failed to create cgroup\n");
>   
> @@ -90,3 +295,50 @@ int igt_simple_main()
>   	igt_cgroup_dmem_regions_free(regions);
>   	igt_cgroup_free(cg);
>   }
> +
> +int igt_main()
> +{
> +	igt_fixture() {
> +		igt_require_f(getuid() == 0, "Test requires root\n");
> +		/* Check dmem cgroup controller is available before doing anything else */
> +		igt_require_f(igt_cgroup_dmem_available(),
> +			      "dmem cgroup controller not available (no cgroup v2 or no registered regions)\n");
> +
> +	}
> +
> +	igt_subtest("simple")
> +		simple_cgroup();
> +
> +	for (int d = 0; drivers[d].driver; d++) {
> +		igt_subtest_group() {
> +			int fd = -1;
> +			int ret = -1;
> +			char *cg_region = NULL;
> +			void *ctx = NULL;
> +			igt_fixture() {
> +				fd = drm_open_driver(drivers[d].driver_flag);
> +				igt_require_f(fd >= 0,
> +					"No %s device found, skipping\n",
> +					drivers[d].driver->name);
> +				ret = drivers[d].driver->init(&ctx, fd);
> +				igt_require_f(ret == 0,
> +					"Failed to initialize %s device, skipping\n",
> +					drivers[d].driver->name);
> +				cg_region = drivers[d].driver->get_region_name(ctx);
> +				igt_require_f(cg_region, "Region not tracked by dmem cgroup controller\n");
> +			}
> +
> +			for (int i = 0; subtests[i].name; i++)
> +				igt_subtest_f("%s-%s", drivers[d].driver->name, subtests[i].name)
> +					subtests[i].test_fn(fd, cg_region, subtests[i].flags, drivers[d].driver, ctx);
> +
> +			igt_fixture() {
> +				if (!ret)
> +					drivers[d].driver->deinit(ctx);
> +				if (fd >= 0)
> +					drm_close_driver(fd);
> +				free(cg_region);
> +			}
> +		}
> +	}
> +}
> 

Re: [PATCH i-g-t v6 8/9] tests/cgroup_dmem: add dmem cgroup eviction test

[Tvrtko Ursulin]

On 03/09/2026 23:00, Thadeu Lima de Souza Cascardo wrote:
> From: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> 
> The write_eviction subtest:
>   - Creates a sub-cgroup and moves the test process into it.
>   - Sets a dmem.max limit on the first VRAM region (up to 4 GiB, or
>     the full capacity if smaller).
> - Fills VRAM by repeatedly creating BOs placed in VRAM, depending on card
>    support.
>   - Verifies that cgroup current usage is within the expected range when
>     the limit is hit.
>   - Lowers dmem.max in 128 MiB steps, waiting for usage to follow each
>     reduction.
> 
> The write_eviction_interruptible subtest runs the same test with
> SIGCONT signals injected via igt_fork_signal_helper() and reports the
> number of signals received.  When a signal interrupts kernel-side
> eviction, a small BO allocation is used to re-trigger it.
> 
> Assisted-by: GitHub Copilot:claude-sonnet-4.6
> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
> ---
>   tests/cgroup_dmem.c | 149 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 149 insertions(+)
> 
> diff --git a/tests/cgroup_dmem.c b/tests/cgroup_dmem.c
> index ba5e6a2e3deb..0d3b415acd54 100644
> --- a/tests/cgroup_dmem.c
> +++ b/tests/cgroup_dmem.c
> @@ -36,9 +36,12 @@
>   
>   #define BO_SIZE			SZ_64M
>   #define MAX_LIMIT		((uint64_t)4 * SZ_1G)
> +#define EVICT_STEP		SZ_128M
>   #define USAGE_POLL_MS		10
>   #define USAGE_DROP_TIMEOUT_MS	1000
>   
> +#define TEST_INTERRUPTIBLE	(1 << 0)
> +
>   /**
>    * SUBTEST: simple
>    * DESCRIPTION:
> @@ -61,6 +64,62 @@
>    * REQUIREMENTS: xe or amdgpu device with at least one VRAM region
>    */
>   
> +/**
> + * SUBTEST: write_eviction
> + * DESCRIPTION:
> + *   Create a dmem cgroup, move the current process into it and set the max
> + *   device memory limit for the first VRAM region to 4 GiB.  Then fill VRAM
> + *   by creating BOs with %DRM_XE_GEM_CREATE_FLAG_DEFER_BACKING (so that the
> + *   physical allocation is deferred until VM_BIND) and binding them into an
> + *   LR VM until the cgroup limit is hit.  Verify that the reported cgroup
> + *   current usage is within the expected range when the error occurs.
> + *   Finally lower the max limit in 256 MiB steps and verify that the cgroup
> + *   usage follows.
> + * REQUIREMENTS: must run as root; xe device with at least one VRAM region

It feels that adding an explicit igt_require(DRIVER_XE) to the test 
would be a good move.

> + */
> +
> +/**
> + * SUBTEST: write_eviction_interruptible
> + * DESCRIPTION:
> + *   Same as write_eviction but with SIGCONT signals injected throughout via
> + *   igt_fork_signal_helper() to verify that the dmem.max write path handles
> + *   signal interruption correctly.  A signal handler counts received signals
> + *   and the count is reported as debug output at the end of the test.
> + *   A signal interrupts the set-time eviction, and further eviction can be
> + *   triggered by an explicit allocation.
> + * REQUIREMENTS: must run as root; xe device with at least one VRAM region
> + */
> +
> +static atomic_int signal_count;
> +static struct sigaction sigcont_oldact;
> +
> +static void sigcont_handler(int sig)
> +{
> +	atomic_fetch_add(&signal_count, 1);
> +
> +	/* Chain to the previous handler (IGT's dummy sig_handler) */
> +	if (sigcont_oldact.sa_handler &&
> +	    sigcont_oldact.sa_handler != SIG_IGN &&
> +	    sigcont_oldact.sa_handler != SIG_DFL)
> +		sigcont_oldact.sa_handler(sig);
> +}
> +
> +static void install_sigcont_counter(void)
> +{
> +	struct sigaction sa;
> +
> +	atomic_store(&signal_count, 0);
> +	igt_fork_signal_helper();
> +	/*
> +	 * Install the counter after igt_fork_signal_helper() so our handler
> +	 * is not overwritten.  Save the old handler so we can chain to it.
> +	 */
> +	memset(&sa, 0, sizeof(sa));
> +	sa.sa_handler = sigcont_handler;
> +	sigemptyset(&sa.sa_mask);
> +	sigaction(SIGCONT, &sa, &sigcont_oldact);
> +}
> +
>   static uint64_t wait_for_usage_drop(struct igt_cgroup *cg, const char *region,
>   				    uint64_t limit)
>   {
> @@ -213,12 +272,102 @@ static void test_current(int fd, char *cg_region, unsigned int flags, const stru
>   	igt_cgroup_free(cg);
>   }
>   
> +static void test_write_eviction(int fd, char *cg_region, unsigned int flags, const struct igt_dmem_driver *drv, void *ctx)
> +{
> +	struct igt_cgroup *cg;
> +	void **handles;
> +	int max_bo;
> +	uint64_t current, capacity, cg_max, limit, after;
> +	int err;
> +
> +	igt_cgroup_dmem_get_capacity(cg_region, &capacity);
> +	igt_require_f(capacity >= 4 * BO_SIZE,
> +		      "VRAM capacity (%"PRIu64" MiB) too small to test\n",
> +		      capacity / SZ_1M);
> +
> +	/*
> +	 * Use up to 4 GiB, or the full capacity if the device has less.
> +	 * Leave one BO_SIZE worth of headroom so the device isn't completely
> +	 * exhausted before the cgroup limit is hit.
> +	 */
> +	cg_max = min(MAX_LIMIT, capacity - BO_SIZE);
> +	cg_max = ALIGN_DOWN(cg_max, EVICT_STEP);
> +
> +	if (flags & TEST_INTERRUPTIBLE)
> +		install_sigcont_counter();

I stumbled upon IGT docs recommending igt_while_interruptible as a 
gentler alternative. Would that still work here and be simpler?

> +
> +	/* Create cgroup and move into it */
> +	cg = igt_cgroup_new("igt_cgroups_test");
> +	igt_cgroup_move_current(cg);
> +	igt_cgroup_dmem_set_max(cg, cg_region, cg_max, false);
> +
> +	max_bo = (cg_max / BO_SIZE) + 8; /* headroom for overcommit */
> +
> +	handles = calloc(max_bo, sizeof(handles[0]));
> +	igt_assert_f(handles, "failed to allocate handles array");
> +
> +	allocate_vram(handles, drv, ctx, max_bo, BO_SIZE);
> +
> +	igt_cgroup_dmem_get_current(cg, cg_region, &current);
> +	igt_debug("After fill: cgroup current = %"PRIu64" MiB, "
> +		  "max = %"PRIu64" MiB\n",
> +		  current / SZ_1M, cg_max / SZ_1M);
> +
> +	igt_assert_f(current <= cg_max,
> +		     "Usage %"PRIu64" MiB exceeds max %"PRIu64" MiB + slack\n",
> +		     current / SZ_1M, cg_max / SZ_1M);
> +
> +	/* Phase 2: lower max in 256 MiB steps, verify usage follows */
> +	limit = cg_max;
> +	while (limit >= EVICT_STEP) {
> +
> +		limit -= EVICT_STEP;
> +		igt_cgroup_dmem_set_max(cg, cg_region, limit, false);
> +
> +		igt_cgroup_dmem_get_current(cg, cg_region, &after);
> +		igt_debug("Lowered max to %"PRIu64" MiB: usage = %"PRIu64" MiB\n",
> +			  limit / SZ_1M, after / SZ_1M);
> +
> +		if (limit > EVICT_STEP) {
> +			if ((flags & TEST_INTERRUPTIBLE) && after > limit) {
> +				/* Let a new bo creation trigger eviction. */
> +				void *handle;
> +				err = drv->allocate_vram(ctx, BO_SIZE / 8, &handle);
> +				igt_assert_f(err == 0,
> +					"Error trying to allocate more VRAM to trigger eviction.");
> +				drv->free_vram(ctx, handle);
> +
> +				igt_cgroup_dmem_get_current(cg, cg_region, &after);
> +				igt_debug("Forced eviction max is %"PRIu64
> +					  " MiB: usage = %"PRIu64" MiB\n",
> +					  limit / SZ_1M, after / SZ_1M);
> +			}
> +
> +			igt_assert_f(after <= limit,
> +				     "Usage %"PRIu64" MiB did not follow max %"PRIu64" MiB\n",
> +				     after / SZ_1M, limit / SZ_1M);

I was quite confused by what is the interrupt by signal business about. 
My best guess is the point is not to interrupt the write to the sysfs on 
the superficial level, but to interrupt the actual eviction process 
which happens during the write? Is that a cgroup requirement that the 
new limit has to become effective (or attempted at least) during the 
write itself? And once interrupted it will not re-try it until new 
"activity" in the dmem cgroup happens (the dummy allocation above)?

Regards,

Tvrtko

> +		}
> +	}
> +
> +	if (flags & TEST_INTERRUPTIBLE) {
> +		igt_stop_signal_helper();
> +		igt_info("Signals received during test: %d\n",
> +			 atomic_load(&signal_count));
> +	}
> +
> +	/* Cleanup */
> +	igt_cgroup_dmem_set_max(cg, cg_region, IGT_CGROUP_DMEM_MAX, false);
> +	igt_cgroup_free(cg);
> +}
> +
>   static const struct {
>   	const char *name;
>   	void (*test_fn)(int fd, char *cg_region, unsigned int flags, const struct igt_dmem_driver *drv, void *ctx);
>   	unsigned int flags;
>   } subtests[] = {
>   	{ "current", test_current, 0 },
> +	{ "write_eviction", test_write_eviction, 0 },
> +	{ "write_eviction_interruptible", test_write_eviction, TEST_INTERRUPTIBLE },
>   	{ }
>   };
>   
> 

Re: [PATCH i-g-t v6 9/9] tests/cgroup_dmem: add write_eviction_nonblock subtest

[Tvrtko Ursulin]

On 03/09/2026 23:00, Thadeu Lima de Souza Cascardo wrote:
> From: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> 
> Add write_eviction_nonblock to exercise the O_NONBLOCK path of the dmem
> cgroup max interface.  After filling VRAM to the cgroup limit, each
> limit-lowering step writes dmem.max with O_NONBLOCK so that synchronous
> eviction is skipped.  The test then verifies that usage has not yet
> dropped below the new limit, allocates a small BO to trigger eviction
> explicitly, and finally confirms that usage falls within bounds.
> 
> Assisted-by: GitHub Copilot:claude-sonnet-4.6
> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
> ---
>   tests/cgroup_dmem.c | 37 ++++++++++++++++++++++++++++++++++---
>   1 file changed, 34 insertions(+), 3 deletions(-)
> 
> diff --git a/tests/cgroup_dmem.c b/tests/cgroup_dmem.c
> index 0d3b415acd54..ee6345c17878 100644
> --- a/tests/cgroup_dmem.c
> +++ b/tests/cgroup_dmem.c
> @@ -41,6 +41,7 @@
>   #define USAGE_DROP_TIMEOUT_MS	1000
>   
>   #define TEST_INTERRUPTIBLE	(1 << 0)
> +#define TEST_NONBLOCK		(1 << 1)
>   
>   /**
>    * SUBTEST: simple
> @@ -90,6 +91,18 @@
>    * REQUIREMENTS: must run as root; xe device with at least one VRAM region
>    */
>   
> +/**
> + * SUBTEST: write_eviction_nonblock
> + * DESCRIPTION:
> + *   Same fill phase as write_eviction.  In the limit-lowering phase dmem.max
> + *   is written with O_NONBLOCK, which causes the kernel to skip synchronous
> + *   eviction.  After each nonblock write the test verifies that usage has not
> + *   yet dropped below the new limit, then triggers eviction explicitly by
> + *   allocating a small BO.  Finally verifies that usage falls within bounds
> + *   after the forced eviction.
> + * REQUIREMENTS: must run as root; xe device with at least one VRAM region
> + */
> +
>   static atomic_int signal_count;
>   static struct sigaction sigcont_oldact;
>   
> @@ -277,7 +290,7 @@ static void test_write_eviction(int fd, char *cg_region, unsigned int flags, con
>   	struct igt_cgroup *cg;
>   	void **handles;
>   	int max_bo;
> -	uint64_t current, capacity, cg_max, limit, after;
> +	uint64_t current, capacity, cg_max, limit, after, before;
>   	int err;
>   
>   	igt_cgroup_dmem_get_capacity(cg_region, &capacity);
> @@ -322,14 +335,31 @@ static void test_write_eviction(int fd, char *cg_region, unsigned int flags, con
>   	while (limit >= EVICT_STEP) {
>   
>   		limit -= EVICT_STEP;
> -		igt_cgroup_dmem_set_max(cg, cg_region, limit, false);
> +
> +		if (flags & TEST_NONBLOCK)
> +			igt_cgroup_dmem_get_current(cg, cg_region, &before);
> +
> +		igt_cgroup_dmem_set_max(cg, cg_region, limit,
> +					!!(flags & TEST_NONBLOCK));
>   
>   		igt_cgroup_dmem_get_current(cg, cg_region, &after);
>   		igt_debug("Lowered max to %"PRIu64" MiB: usage = %"PRIu64" MiB\n",
>   			  limit / SZ_1M, after / SZ_1M);
>   
> +		if (flags & TEST_NONBLOCK) {
> +			/*
> +			 * O_NONBLOCK skips eviction: verify usage has not
> +			 * dropped below the new limit yet.
> +			 */

Is this userspace ABI contract or happens to be? It feels odd - even if 
we ask for non block for the write why would kernel not be allowed to do 
stuff behind the covers?

Regards,

Tvrtko

> +			igt_assert_f(after == before,
> +				     "Expected no eviction with O_NONBLOCK, but "
> +				     "usage dropped from %"PRIu64" MiB to %"PRIu64" MiB "
> +				     "(limit %"PRIu64" MiB)\n",
> +				     before / SZ_1M, after / SZ_1M, limit / SZ_1M);
> +		}
> +
>   		if (limit > EVICT_STEP) {
> -			if ((flags & TEST_INTERRUPTIBLE) && after > limit) {
> +			if ((flags & (TEST_INTERRUPTIBLE | TEST_NONBLOCK)) && after > limit) {
>   				/* Let a new bo creation trigger eviction. */
>   				void *handle;
>   				err = drv->allocate_vram(ctx, BO_SIZE / 8, &handle);
> @@ -368,6 +398,7 @@ static const struct {
>   	{ "current", test_current, 0 },
>   	{ "write_eviction", test_write_eviction, 0 },
>   	{ "write_eviction_interruptible", test_write_eviction, TEST_INTERRUPTIBLE },
> +	{ "write_eviction_nonblock", test_write_eviction, TEST_NONBLOCK },
>   	{ }
>   };
>   
>