Attempt a PMD sized PFN insertion into the VMA if the faulty address of the fault handler is part of a huge page.
On builds with CONFIG_TRANSPARENT_HUGEPAGE enabled, if the mmap() user address is PMD size aligned, if the GEM object is backed by shmem buffers on mountpoints setting the 'huge=' option and if the shmem backing store manages to allocate a huge folio, CPU mapping would then benefit from significantly increased memcpy() performance. When these conditions are met on a system with 2 MiB huge pages, an aligned copy of 2 MiB would raise a single page fault instead of 4096. v4: - implement map_pages instead of huge_fault v6: - get rid of map_pages handler for now (keep it for another series along with arm64 contpte support) v11: - remove page fault validity check helper - rename drm_gem_shmem_map_pmd() to drm_gem_shmem_try_map_pmd() - add Boris R-b v12: - move up ret var decl in fault handler to minimize diff Signed-off-by: Loïc Molinari <[email protected]> Reviewed-by: Boris Brezillon <[email protected]> --- drivers/gpu/drm/drm_gem_shmem_helper.c | 35 +++++++++++++++++++++++--- 1 file changed, 31 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c index e47ab3ebb5c2..e67216cbb469 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -567,6 +567,26 @@ int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev, } EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create); +static bool drm_gem_shmem_try_map_pmd(struct vm_fault *vmf, unsigned long addr, + struct page *page) +{ +#ifdef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP + unsigned long pfn = page_to_pfn(page); + unsigned long paddr = pfn << PAGE_SHIFT; + bool aligned = (addr & ~PMD_MASK) == (paddr & ~PMD_MASK); + + if (aligned && + pmd_none(*vmf->pmd) && + folio_test_pmd_mappable(page_folio(page))) { + pfn &= PMD_MASK >> PAGE_SHIFT; + if (vmf_insert_pfn_pmd(vmf, pfn, false) == VM_FAULT_NOPAGE) + return true; + } +#endif + + return false; +} + static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf) { struct vm_area_struct *vma = vmf->vma; @@ -574,8 +594,9 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf) struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj); loff_t num_pages = obj->size >> PAGE_SHIFT; vm_fault_t ret; - struct page *page; + struct page **pages = shmem->pages; pgoff_t page_offset; + unsigned long pfn; /* Offset to faulty address in the VMA. */ page_offset = vmf->pgoff - vma->vm_pgoff; @@ -586,12 +607,18 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf) drm_WARN_ON_ONCE(obj->dev, !shmem->pages) || shmem->madv < 0) { ret = VM_FAULT_SIGBUS; - } else { - page = shmem->pages[page_offset]; + goto out; + } - ret = vmf_insert_pfn(vma, vmf->address, page_to_pfn(page)); + if (drm_gem_shmem_try_map_pmd(vmf, vmf->address, pages[page_offset])) { + ret = VM_FAULT_NOPAGE; + goto out; } + pfn = page_to_pfn(pages[page_offset]); + ret = vmf_insert_pfn(vma, vmf->address, pfn); + + out: dma_resv_unlock(shmem->base.resv); return ret; -- 2.47.3
