gpu: nvgpu: WAR for simulator bug

On linsim, when the push buffers are allowed to be allocated with small
pages above 4GB the simulator crashes. This patch ensures that for
linsim all small page allocations are forced to be below 4GB in the
GPU VA space. By doing so the simulator no longer crashes.

This bug has come up because the GPU buddy allocator work generates
allocations at the top of the address space first. Thus push buffers
were located at between 12GB and 16GB in the GPU VA space.

Change-Id: Iaef0af3fda3f37ac09a66b5e1179527d6fe08ccc
Signed-off-by: Alex Waterman <alexw@nvidia.com>
Reviewed-on: http://git-master/r/740728
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Tested-by: Terje Bergstrom <tbergstrom@nvidia.com>

1 files changed, 10 insertions, 3 deletions

diff --git a/drivers/gpu/nvgpu/gk20a/mm_gk20a.c b/drivers/gpu/nvgpu/gk20a/mm_gk20a.c
index 7d359ff4..5d1ff563 100644
--- a/drivers/gpu/nvgpu/gk20a/mm_gk20a.c
+++ b/drivers/gpu/nvgpu/gk20a/mm_gk20a.c
@@ -1437,7 +1437,7 @@ u64 gk20a_vm_map(struct vm_gk20a *vm,
          * the alignment determined by gmmu_select_page_size().
          */
         if (flags & NVGPU_AS_MAP_BUFFER_FLAGS_FIXED_OFFSET) {
-                int pgsz_idx = NV_GMMU_VA_IS_UPPER(offset_align) ?
+                int pgsz_idx = __nv_gmmu_va_is_upper(vm, offset_align) ?
                                 gmmu_page_size_big : gmmu_page_size_small;
                 if (pgsz_idx > bfr.pgsz_idx) {
                         gk20a_err(d, "%llx buffer pgsz %d, VA pgsz %d",
@@ -2441,6 +2441,13 @@ int gk20a_init_vm(struct mm_gk20a *mm,
         /* note: keep the page sizes sorted lowest to highest here */
         u32 gmmu_page_sizes[gmmu_nr_page_sizes] = { SZ_4K, big_page_size };
 
+        /*
+         * Linsim bug: seems like we can't have pushbuffers above 4GB. Easy WAR for sim
+         * is to just limit the address space to 4GB.
+         */
+        if (tegra_platform_is_linsim() && aperture_size > SZ_4G)
+                aperture_size = SZ_4G;
+
         vm->mm = mm;
 
         vm->va_start = low_hole;
@@ -2483,7 +2490,7 @@ int gk20a_init_vm(struct mm_gk20a *mm,
          * remains is allocated to large pages. */
         small_vma_size = vm->va_limit;
         if (big_pages) {
-                small_vma_size = (u64)16 << 30;
+                small_vma_size = __nv_gmmu_va_small_page_limit();
                 large_vma_size = vm->va_limit - small_vma_size;
         }
 
@@ -2698,7 +2705,7 @@ int gk20a_vm_free_space(struct gk20a_as_share *as_share,
                         args->pages, args->offset);
 
         /* determine pagesz idx */
-        pgsz_idx = NV_GMMU_VA_IS_UPPER(args->offset) ?
+        pgsz_idx = __nv_gmmu_va_is_upper(vm, args->offset) ?
                         gmmu_page_size_big : gmmu_page_size_small;
 
         start_page_nr = (u32)(args->offset >>