amd/amdkfd: correct mem limit calculation for small APUs

Current mem limit check leaks some GTT memory (reserved_for_pt
reserved_for_ras + adev->vram_pin_size) for small APUs.

Since carveout VRAM is tunable on APUs, there are three case
regarding the carveout VRAM size relative to GTT:

1. 0 < carveout < gtt
   apu_prefer_gtt = true, is_app_apu = false

2. carveout > gtt / 2
   apu_prefer_gtt = false, is_app_apu = false

3. 0 = carveout
   apu_prefer_gtt = true, is_app_apu = true

It doesn't make sense to check below limitation in case 1
(default case, small carveout) because the values in the below
expression are mixed with carveout and gtt.

adev->kfd.vram_used[xcp_id] + vram_needed >
    vram_size - reserved_for_pt - reserved_for_ras -
    atomic64_read(&adev->vram_pin_size)

gtt: kfd.vram_used, vram_needed, vram_size
carveout: reserved_for_pt, reserved_for_ras, adev->vram_pin_size

In case 1, vram allocation will go to gtt domain, skip vram check
since ttm_mem_limit check already cover this allocation.

Signed-off-by: Yifan Zhang <yifan1.zhang@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit fa7c99f04f6dd299388e9282812b14e95558ac8e)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
index 260165bbe3736dc369d5bfa718020ec98d1c8698..b16cce7c22c3733305018ea56757e2fbe90fdf86 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
@@ -213,19 +213,35 @@ int amdgpu_amdkfd_reserve_mem_limit(struct amdgpu_device *adev,
        spin_lock(&kfd_mem_limit.mem_limit_lock);
 
        if (kfd_mem_limit.system_mem_used + system_mem_needed >
-           kfd_mem_limit.max_system_mem_limit)
+           kfd_mem_limit.max_system_mem_limit) {
                pr_debug("Set no_system_mem_limit=1 if using shared memory\n");
+               if (!no_system_mem_limit) {
+                       ret = -ENOMEM;
+                       goto release;
+               }
+       }
 
-       if ((kfd_mem_limit.system_mem_used + system_mem_needed >
-            kfd_mem_limit.max_system_mem_limit && !no_system_mem_limit) ||
-           (kfd_mem_limit.ttm_mem_used + ttm_mem_needed >
-            kfd_mem_limit.max_ttm_mem_limit) ||
-           (adev && xcp_id >= 0 && adev->kfd.vram_used[xcp_id] + vram_needed >
-            vram_size - reserved_for_pt - reserved_for_ras - atomic64_read(&adev->vram_pin_size))) {
+       if (kfd_mem_limit.ttm_mem_used + ttm_mem_needed >
+               kfd_mem_limit.max_ttm_mem_limit) {
                ret = -ENOMEM;
                goto release;
        }
 
+       /*if is_app_apu is false and apu_prefer_gtt is true, it is an APU with
+        * carve out < gtt. In that case, VRAM allocation will go to gtt domain, skip
+        * VRAM check since ttm_mem_limit check already cover this allocation
+        */
+
+       if (adev && xcp_id >= 0 && (!adev->apu_prefer_gtt || adev->gmc.is_app_apu)) {
+               uint64_t vram_available =
+                       vram_size - reserved_for_pt - reserved_for_ras -
+                       atomic64_read(&adev->vram_pin_size);
+               if (adev->kfd.vram_used[xcp_id] + vram_needed > vram_available) {
+                       ret = -ENOMEM;
+                       goto release;
+               }
+       }
+
        /* Update memory accounting by decreasing available system
         * memory, TTM memory and GPU memory as computed above
         */
@@ -1626,11 +1642,15 @@ size_t amdgpu_amdkfd_get_available_memory(struct amdgpu_device *adev,
        uint64_t vram_available, system_mem_available, ttm_mem_available;
 
        spin_lock(&kfd_mem_limit.mem_limit_lock);
-       vram_available = KFD_XCP_MEMORY_SIZE(adev, xcp_id)
-               - adev->kfd.vram_used_aligned[xcp_id]
-               - atomic64_read(&adev->vram_pin_size)
-               - reserved_for_pt
-               - reserved_for_ras;
+       if (adev->apu_prefer_gtt && !adev->gmc.is_app_apu)
+               vram_available = KFD_XCP_MEMORY_SIZE(adev, xcp_id)
+                       - adev->kfd.vram_used_aligned[xcp_id];
+       else
+               vram_available = KFD_XCP_MEMORY_SIZE(adev, xcp_id)
+                       - adev->kfd.vram_used_aligned[xcp_id]
+                       - atomic64_read(&adev->vram_pin_size)
+                       - reserved_for_pt
+                       - reserved_for_ras;
 
        if (adev->apu_prefer_gtt) {
                system_mem_available = no_system_mem_limit ?