On Wed, Jun 14, 2023 at 05:30:25PM +0200, Thomas Hellström (Intel) wrote: > > On 6/14/23 15:22, Tvrtko Ursulin wrote: > > > > On 14/06/2023 13:35, Sumitra Sharma wrote: > > > Pages allocated with GFP_KERNEL cannot come from Highmem. > > > That is why there is no need to call kmap() on them. > > > > Are you sure it is GFP_KERNEL backed and not tmpfs? I am not sure myself > > so let me copy Matt and Thomas if they happen to know off hand. > Hello, Yes it is true that the pages have not been acquired using the GFP_KERNEL. I confused the allocation of the struct 'i915_vma_resource' tracking the pages with the allocation of the pages themselves. This was noted by my mentor Ira Weiny <ira.weiny@xxxxxxxxx>. > It looks to me these are shmem pages or TTM pages. Both could be highmem. So > I think kmap is the correct choice here. > However, the kmap() will not be the correct choice here and kmap_local_page() must be used instead. I have created a v2 patch for the same https://lore.kernel.org/lkml/20230617180420.GA410966@xxxxxxxxxxx/ Thank you for helping me. Regards Sumitra > /Thomas > > > > > > > > Regards, > > > > Tvrtko > > > > > Therefore, don't call kmap() on the page coming from > > > vma_res->bi.pages using for_each_sgt_page() in > > > i915_vma_coredump_create(). > > > > > > Use a plain page_address() to get the kernel address instead. > > > > > > Signed-off-by: Sumitra Sharma <sumitraartsy@xxxxxxxxx> > > > --- > > > drivers/gpu/drm/i915/i915_gpu_error.c | 3 +-- > > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c > > > b/drivers/gpu/drm/i915/i915_gpu_error.c > > > index f020c0086fbc..6f51cb4fc55c 100644 > > > --- a/drivers/gpu/drm/i915/i915_gpu_error.c > > > +++ b/drivers/gpu/drm/i915/i915_gpu_error.c > > > @@ -1164,9 +1164,8 @@ i915_vma_coredump_create(const struct intel_gt > > > *gt, > > > drm_clflush_pages(&page, 1); > > > - s = kmap(page); > > > + s = page_address(page); > > > ret = compress_page(compress, s, dst, false); > > > - kunmap(page); > > > drm_clflush_pages(&page, 1);
