Re: [PATCH i-g-t v7 4/9] tests/intel/xe_madvise: Add purged-mmap-blocked subtest

["Sharma, Nishit" <nishit.sharma@intel.com>]

On 4/9/2026 12:31 PM, Arvind Yadav wrote:
> Add a new purged-mmap-blocked subtest that triggers an actual purge
> via memory pressure and verifies that mmap() fails with -EINVAL once
> the BO backing store has been permanently discarded.
>
> The purgeable check moved from xe_gem_mmap_offset_ioctl()
> into a new xe_gem_object_mmap() callback, so the blocking point is now
> mmap() itself rather than the mmap offset ioctl:
>
>    - DRM_IOCTL_XE_GEM_MMAP_OFFSET: always succeeds regardless of
>      purgeable state (just returns the pre-allocated offset)
>    - mmap() on DONTNEED BO: fails with -EBUSY (temporary state)
>    - mmap() on purged BO: fails with -EINVAL (permanent, no backing store)
>
> v5:
>    - Add purged-mmap-blocked subtest to verify mmap is blocked after
>      BO backing store is permanently purged.
>
> v6:
>    - DRM_IOCTL_XE_GEM_MMAP_OFFSET always succeeds; the purgeable check
>      now happens in xe_gem_object_mmap() at mmap() time. For purged BOs,
>      assert mmap() fails with -EINVAL.
>
> v7:
>    - Moved trigger_memory_pressure() and purgeable_mark_and_verify_purged()
>      here. (Nishit)
>    - Use xe_has_vram() instead of checking xe_visible_vram_size() > 0 for
>      clearer dGPU/iGPU detection. (Nishit)
>    - Fix purgeable_mark_and_verify_purged(): handle retained == 0 from
>      DONTNEED (BO already purged) as success instead of incorrectly
>      returning false. (Nishit)
>    - Drop unused vm parameter from trigger_memory_pressure(). (Nishit)
>
> Cc: Nishit Sharma <nishit.sharma@intel.com>
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
> Cc: Pravalika Gurram <pravalika.gurram@intel.com>
> Signed-off-by: Arvind Yadav <arvind.yadav@intel.com>
> ---
>   tests/intel/xe_madvise.c | 136 +++++++++++++++++++++++++++++++++++++++
>   1 file changed, 136 insertions(+)
>
> diff --git a/tests/intel/xe_madvise.c b/tests/intel/xe_madvise.c
> index 2c8c27fa9..619d64b46 100644
> --- a/tests/intel/xe_madvise.c
> +++ b/tests/intel/xe_madvise.c
> @@ -59,6 +59,136 @@ static void purgeable_setup_simple_bo(int fd, uint32_t *vm, uint32_t *bo,
>   	xe_wait_ufence(fd, &sync_val, 1, 0, NSEC_PER_SEC);
>   }
>   
> +/**
> + * trigger_memory_pressure - Fill VRAM/RAM + 50% to force purgeable reclaim
> + * @fd: DRM file descriptor
> + *
> + * Allocates BOs in a temporary VM until memory is overcommitted by 50%,
> + * forcing the kernel to purge DONTNEED-marked BOs.
> + */
> +static void trigger_memory_pressure(int fd)
> +{
> +	uint64_t mem_size, overpressure;
> +	const uint64_t chunk = 8ull << 20; /* 8 MiB */
> +	int max_objs, n = 0;
> +	uint32_t *handles;
> +	uint64_t total;
> +	void *p;
> +	uint32_t handle, vm;
> +
> +	/* Use a separate VM so pressure BOs don't affect the test VM */
> +	vm = xe_vm_create(fd, 0, 0);
> +
> +	/* Purgeable BOs reside in VRAM (dGPU) or system memory (iGPU) */
> +	mem_size = xe_has_vram(fd) ? xe_visible_vram_size(fd, 0) :
> +		   igt_get_total_ram_mb() << 20;
> +
> +	/* Scale overpressure to 50% of memory, minimum 64MB */
> +	overpressure = mem_size / 2;
> +	if (overpressure < (64 << 20))
> +		overpressure = 64 << 20;
> +
> +	max_objs = (mem_size + overpressure) / chunk + 1;
> +	handles = malloc(max_objs * sizeof(*handles));
> +	igt_assert(handles);
> +
> +	total = 0;
> +	while (total < mem_size + overpressure && n < max_objs) {
> +		uint32_t err;
> +
> +		err = __xe_bo_create(fd, vm, chunk,
> +				     vram_if_possible(fd, 0),
> +				     DRM_XE_GEM_CREATE_FLAG_NEEDS_VISIBLE_VRAM,
> +				     NULL, &handle);
> +		if (err) /* Out of memory — sufficient pressure achieved */
> +			break;
> +
> +		handles[n++] = handle;
> +		total += chunk;
> +
> +		p = xe_bo_map(fd, handle, chunk);
> +		igt_assert(p != MAP_FAILED);
> +
> +		/* Fault in all pages so they actually consume memory */
> +		memset(p, 0xCD, chunk);
> +		munmap(p, chunk);
> +	}
> +
> +	/* Allow shrinker time to process pressure */
> +	usleep(100000);
> +
> +	for (int i = 0; i < n; i++)
> +		gem_close(fd, handles[i]);
> +
> +	free(handles);
> +
> +	xe_vm_destroy(fd, vm);
> +}
> +
> +/**
> + * purgeable_mark_and_verify_purged - Mark DONTNEED, pressure, check purged
> + * @fd: DRM file descriptor
> + * @vm: VM handle
> + * @addr: Virtual address of the BO
> + * @size: Size of the BO
> + *
> + * Returns true if the BO was purged under memory pressure.
> + */
> +static bool purgeable_mark_and_verify_purged(int fd, uint32_t vm, uint64_t addr, size_t size)
> +{
> +	uint32_t retained;
> +
> +	/* Mark as DONTNEED */
> +	retained = xe_vm_madvise_purgeable(fd, vm, addr, size,
> +					   DRM_XE_VMA_PURGEABLE_STATE_DONTNEED);
> +	if (retained == 0)
> +		return true; /* Already purged */
> +
> +	/* Trigger memory pressure */
> +	trigger_memory_pressure(fd);
> +
> +	/* Verify purged */
> +	retained = xe_vm_madvise_purgeable(fd, vm, addr, size,
> +					   DRM_XE_VMA_PURGEABLE_STATE_WILLNEED);
> +	return retained == 0;
> +}
> +
> +/**
> + * SUBTEST: purged-mmap-blocked
> + * Description: After BO is purged, verify mmap() fails with -EINVAL
> + * Test category: functionality test
> + */
> +static void test_purged_mmap_blocked(int fd)
> +{
> +	uint32_t bo, vm;
> +	uint64_t addr = PURGEABLE_ADDR;
> +	size_t bo_size = PURGEABLE_BO_SIZE;
> +	struct drm_xe_gem_mmap_offset mmo = {};
> +	void *ptr;
> +
> +	purgeable_setup_simple_bo(fd, &vm, &bo, addr, bo_size, false);
> +	if (!purgeable_mark_and_verify_purged(fd, vm, addr, bo_size)) {
> +		gem_close(fd, bo);
> +		xe_vm_destroy(fd, vm);
> +		igt_skip("Unable to induce purge on this platform/config");
small nit: here skip message reflecting purge support unavailability in 
platform/config, Simple mention Unable to induce purge.
> +	}
> +
> +	/*
> +	 * Getting the mmap offset is always allowed regardless of purgeable
> +	 * state - the blocking happens at mmap() time (xe_gem_object_mmap).
> +	 * For a purged BO, mmap() must fail with -EINVAL (no backing store).
> +	 */
> +	mmo.handle = bo;
> +	igt_assert_eq(igt_ioctl(fd, DRM_IOCTL_XE_GEM_MMAP_OFFSET, &mmo), 0);
> +
> +	ptr = mmap(NULL, bo_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, mmo.offset);
> +	igt_assert_eq_u64((uint64_t)ptr, (uint64_t)MAP_FAILED);
> +	igt_assert_eq(errno, EINVAL);
> +
> +	gem_close(fd, bo);
> +	xe_vm_destroy(fd, vm);
> +}
> +
>   /**
>    * SUBTEST: dontneed-before-mmap
>    * Description: Mark BO as DONTNEED before mmap, verify mmap() fails with -EBUSY
> @@ -115,6 +245,12 @@ int igt_main()
>   			break;
>   		}
>   
> +	igt_subtest("purged-mmap-blocked")
> +		xe_for_each_engine(fd, hwe) {
> +			test_purged_mmap_blocked(fd);
> +			break;
> +		}
> +
>   	igt_fixture() {
>   		xe_device_put(fd);
>   		drm_close_driver(fd);

With above Nit change LGTM:

Reviewed-by: Nishit Sharma <nishit.sharma@intel.com>