Re: [PATCH i-g-t v3 3/8] tests/intel/xe_madvise: Add dontneed-before-mmap subtest

Yadav, Arvind
2026-02-23T09:37:04Z

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On 23-02-2026 11:19, Sharma, Nishit wrote:
>
>
> On 2/23/2026 10:39 AM, Gurram, Pravalika wrote:
>>> -----Original Message-----
>>> From: Yadav, Arvind<arvind.yadav@intel.com>
>>> Sent: Tuesday, 17 February, 2026 08:04 AM
>>> To:igt-dev@lists.freedesktop.org
>>> Cc: Brost, Matthew<matthew.brost@intel.com>; Ghimiray, Himal Prasad
>>> <himal.prasad.ghimiray@intel.com>;thomas.hellstrom@linux.intel.com;
>>> Sharma, Nishit<nishit.sharma@intel.com>; Gurram, Pravalika
>>> <pravalika.gurram@intel.com>
>>> Subject: [PATCH i-g-t v3 3/8] tests/intel/xe_madvise: Add dontneed-before-
>>> mmap subtest
>>>
>>> This test validates kernel behavior when mapping a BO that was already
>>> marked as purgeable and purged before mmap. After purging the BO under
>>> memory pressure, the test attempts to mmap and access it. The kernel should
>>> trigger SIGBUS or SIGSEGV when accessing the purged mapping, confirming
>>> that purged memory is properly invalidated.
>>>
>>> Cc: Nishit Sharma<nishit.sharma@intel.com>
>>> Cc: Pravalika Gurram<pravalika.gurram@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>
>>> Signed-off-by: Arvind Yadav<arvind.yadav@intel.com>
>>> ---
>>> tests/intel/xe_madvise.c | 219
>>> +++++++++++++++++++++++++++++++++++++++
>>> tests/meson.build | 1 +
>>> 2 files changed, 220 insertions(+)
>>> create mode 100644 tests/intel/xe_madvise.c
>>>
>>> diff --git a/tests/intel/xe_madvise.c b/tests/intel/xe_madvise.c new file mode
>>> 100644 index 000000000..7dbe70f42
>>> --- /dev/null
>>> +++ b/tests/intel/xe_madvise.c
>>> @@ -0,0 +1,219 @@
>>> +// SPDX-License-Identifier: MIT
>>> +/*
>>> + * Copyright © 2025 Intel Corporation
>>> + */
>>> +
>>> +/**
>>> + * TEST: Validate purgeable BO madvise functionality
>>> + * Category: Core
>>> + * Mega feature: General Core features
>>> + * Sub-category: Memory management tests
>>> + * Functionality: madvise, purgeable
>>> + */
>>> +
>>> +#include "igt.h"
>>> +#include "xe_drm.h"
>>> +
>>> +#include "xe/xe_ioctl.h"
>>> +#include "xe/xe_query.h"
>>> +
>>> +/* Purgeable test constants */
>>> +#define PURGEABLE_ADDR 0x1a0000
>>> +#define PURGEABLE_BO_SIZE 4096
>>> +
>>> +/**
>>> + * trigger_memory_pressure - Fill VRAM + 25% to force purgeable reclaim
>>> + * @fd: DRM file descriptor
>>> + * @vm: VM handle (unused, kept for API compatibility)
>>> + *
>>> + * Allocates BOs in a temporary VM until VRAM is overcommitted,
>>> + * forcing the kernel to purge DONTNEED-marked BOs.
>>> + */
>>> +static void trigger_memory_pressure(int fd, uint32_t vm) {
>>> + uint64_t vram_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, temp_vm;
>>> +
>>> + /* Use a separate VM so pressure BOs don't affect the test VM */
>>> + temp_vm = xe_vm_create(fd, 0, 0);
>>> +
>>> + vram_size = xe_visible_vram_size(fd, 0);
>>> + /* Scale overpressure to 25% of VRAM, minimum 64MB */
>>> + overpressure = vram_size / 4;
>>> + if (overpressure < (64 << 20))
>>> + overpressure = 64 << 20;
>>> +
>>> + max_objs = (vram_size + overpressure) / chunk + 1;
>>> + handles = malloc(max_objs * sizeof(*handles));
>>> + igt_assert(handles);
>>> +
>>> + total = 0;
>>> + while (total < vram_size + overpressure && n < max_objs) {
>>> + handle = xe_bo_create(fd, temp_vm, chunk,
>>> + vram_if_possible(fd, 0),
>>> +
>>> DRM_XE_GEM_CREATE_FLAG_NEEDS_VISIBLE_VRAM);
>>> + 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 VRAM */
>>> + 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, temp_vm);
>>> +}
>>> +
>>> +static jmp_buf jmp;
>>> +
>>> +__noreturn static void sigtrap(int sig) {
>>> + siglongjmp(jmp, sig);
>>> +}
>>> +
>>> +/**
>>> + * 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 != 1)
>>> + return false;
>>> +
>>> + /* Trigger memory pressure */
>>> + trigger_memory_pressure(fd, vm);
>>> +
>>> + /* Verify purged */
>>> + retained = xe_vm_madvise_purgeable(fd, vm, addr, size,
>>> +
>>> DRM_XE_VMA_PURGEABLE_STATE_WILLNEED);
>>> + return retained == 0;
>>> +}
>>> +
>>> +/**
>>> + * purgeable_setup_simple_bo - Setup VM and bind a single BO
>>> + * @fd: DRM file descriptor
>>> + * @vm: Output VM handle
>>> + * @bo: Output BO handle
>>> + * @addr: Virtual address to bind at
>>> + * @size: Size of the BO
>>> + * @use_scratch: Whether to use scratch page flag
>>> + *
>>> + * Helper to create VM, BO, and bind it at the specified address.
>>> + */
>>> +static void purgeable_setup_simple_bo(int fd, uint32_t *vm, uint32_t *bo,
>>> + uint64_t addr, size_t size, bool
>>> use_scratch) {
>>> + struct drm_xe_sync sync = {
>>> + .type = DRM_XE_SYNC_TYPE_USER_FENCE,
>>> + .flags = DRM_XE_SYNC_FLAG_SIGNAL,
>>> + .timeline_value = 1,
>>> + };
>>> + uint64_t sync_val = 0;
>>> +
>>> + *vm = xe_vm_create(fd, use_scratch ?
>>> DRM_XE_VM_CREATE_FLAG_SCRATCH_PAGE : 0, 0);
>>> + *bo = xe_bo_create(fd, *vm, size, vram_if_possible(fd, 0),
>>> +
>>> DRM_XE_GEM_CREATE_FLAG_NEEDS_VISIBLE_VRAM);
>>> +
>>> + sync.addr = to_user_pointer(&sync_val);
>>> + xe_vm_bind_async(fd, *vm, 0, *bo, 0, addr, size, &sync, 1);
>>> + xe_wait_ufence(fd, &sync_val, 1, 0, NSEC_PER_SEC); }
>>> +
>>> +/**
>>> + * SUBTEST: dontneed-before-mmap
>>> + * Description: Mark BO as DONTNEED before mmap, verify mmap fails or
>>> +SIGBUS on access
>>> + * Test category: functionality test
>>> + */
>>> +static void test_dontneed_before_mmap(int fd, struct
>>> +drm_xe_engine_class_instance *hwe) {
>>> + uint32_t bo, vm;
>>> + uint64_t addr = PURGEABLE_ADDR;
>>> + size_t bo_size = PURGEABLE_BO_SIZE;
>>> + void *map;
>>> +
>>> + purgeable_setup_simple_bo(fd, &vm, &bo, addr, bo_size, false);
>>> + if (!purgeable_mark_and_verify_purged(fd, vm, addr, bo_size))
>>> + igt_skip("Unable to induce purge on this platform/config");
> No cleanup before igt_skip() or it's handled somewhere. gem_close(fd,
> bo) and xe_vm_destroy(fd, vm);

Noted,

>>> +
>>> + /* mmap the purged BO - access should trigger SIGBUS */
>>> + map = xe_bo_map(fd, bo, bo_size);
> Should check igt_assert(map != MAP_FAILED) before using it below.

Noted,

>>> +
>>> + {
>>> + sighandler_t old_sigsegv, old_sigbus;
>>> + char *ptr = (char *)map;
>>> + int sig;
>>> +
>>> + old_sigsegv = signal(SIGSEGV, (__sighandler_t)sigtrap);
>>> + old_sigbus = signal(SIGBUS, (__sighandler_t)sigtrap);
>>> +
>>> + sig = sigsetjmp(jmp, SIGBUS | SIGSEGV);
>>> + switch (sig) {
>>> + case SIGBUS:
>>> + case SIGSEGV:
>>> + /* Expected - purged BO access failed */
>>> + break;
>>> + case 0:
>>> + *ptr = 0;
>>> + __attribute__ ((fallthrough));
>
> why this __attribute__? Any compiler warning? Can't it be handled like
>
> case 0:
>
> default:
>
>     *ptr = 0;
>
> igt_assert_f(false, "Access to purged mmap should trigger SIGBUS, got
> sig=%d\n", sig);
>
> break;
>
> as you are doing intentional fallout from case 0 to default?
>

You're absolutely right! The __attribute__ ((fallthrough)) is
unnecessary here. Your suggested approach is cleaner and more
straightforward.
*ptr = 0 should be part of case 0:

Thanks,
Arvind

>>> + default:
>>> + igt_assert_f(false,
>>> + "Access to purged mmap should trigger
>>> SIGBUS, got sig=%d\n",
>>> + sig);
>>> + break;
>>> + }
>>> +
>>> + signal(SIGBUS, old_sigbus);
>>> + signal(SIGSEGV, old_sigsegv);
>>> + munmap(map, bo_size);
>>> + }
>>> +
>>> + gem_close(fd, bo);
>>> + xe_vm_destroy(fd, vm);
>>> +}
>>> +
>>> +int igt_main()
>>> +{
>>> + struct drm_xe_engine_class_instance *hwe;
>>> + int fd;
>>> +
>>> + igt_fixture() {
>>> + fd = drm_open_driver(DRIVER_XE);
>>> + xe_device_get(fd);
>>> + }
>>> +
>>> + igt_subtest("dontneed-before-mmap")
>>> + xe_for_each_engine(fd, hwe) {
>>> + test_dontneed_before_mmap(fd, hwe);
>>> + break;
>>> + }
>>> +
>>> + igt_fixture() {
>>> + xe_device_put(fd);
>>> + drm_close_driver(fd);
>>> + }
>>> +}
>> Reviewed-by: Pravalika Gurram<pravalika.gurram@intel.com>
>>> diff --git a/tests/meson.build b/tests/meson.build index
>>> 0ad728b87..9d41d7de6 100644
>>> --- a/tests/meson.build
>>> +++ b/tests/meson.build
>>> @@ -313,6 +313,7 @@ intel_xe_progs = [
>>> 'xe_huc_copy',
>>> 'xe_intel_bb',
>>> 'xe_live_ktest',
>>> + 'xe_madvise',
>>> 'xe_media_fill',
>>> 'xe_mmap',
>>> 'xe_module_load',
>>> --
>>> 2.43.0

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