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(unknown [IPv6:2a01:e0a:5e3:6100:826d:bc07:e98c:84a]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: loicmolinari) by bali.collaboradmins.com (Postfix) with ESMTPSA id 7DF5917E055D; Wed, 15 Oct 2025 17:30:32 +0200 (CEST) From: =?UTF-8?q?Lo=C3=AFc=20Molinari?= To: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , Boris Brezillon , Rob Herring , Steven Price , Liviu Dudau , Melissa Wen , =?UTF-8?q?Ma=C3=ADra=20Canal?= , Hugh Dickins , Baolin Wang , Andrew Morton , =?UTF-8?q?Lo=C3=AFc=20Molinari?= , Al Viro , =?UTF-8?q?Miko=C5=82aj=20Wasiak?= , Christian Brauner , Nitin Gote , Andi Shyti , Jonathan Corbet , Christopher Healy , Matthew Wilcox , Bagas Sanjaya Cc: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, kernel@collabora.com Subject: [PATCH v4 03/13] drm/shmem-helper: Map huge pages in fault handlers Date: Wed, 15 Oct 2025 17:30:07 +0200 Message-ID: <20251015153018.43735-4-loic.molinari@collabora.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20251015153018.43735-1-loic.molinari@collabora.com> References: <20251015153018.43735-1-loic.molinari@collabora.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 7B1ED1C001F X-Stat-Signature: 4bpbq9u3zc8gtqbf78fctgndfqbrmkqt X-HE-Tag: 1760542235-779610 X-HE-Meta: U2FsdGVkX1/KuVS/XR4err/csEPIWuuGCPmXP0ndEw3RWaezkEuHlqYWfxa9tVhjI+/fOTQP2W7u8aYh46zocfN1ksl07u2/nWzIsJ9SyYGrbfgVrVXBJiAsTYiSWp89b2fbxO9dHGNCwx21Nn3pYfe0oU0S/uTULIafURScw9FUqw820qriCi+dCEd9Yv78kEXZObRdehMffrUBZ8WQ4ob4A8im+DC6EuEQFCVKTN2HJ967lvKBTsXRgzy/bKR+fq5qvzQENy+8Lgkjznre2hETkXxGaL/fmxot6C+Fdh3SEy8S41/TIBWYs6/euWdqvxJhe38YA1qrsv4/DsaHs7r000dXcGzFjE1iWssclmLLj9Dreedb0NMP5HxiXol6ZZHsWaoUlUPYWaAxTYbXS10zSfyMKNhZSR3V5Qcw+Lr/qFwi8HAuEdcH1B3ws+RSqFRWPHRO5iGOOrit5agKIqLyB2VVNkolDCSpkJejz2jzSrrUJWCIfNYw9q+lWdwUIUeY00au4YWUkEO9lJLi/VGVjEc6zB/dZ//TnDUsui9W7m3ABaxu4xDk8w/dDP1uWHBHTXmI0/hVkImfwh+SUen6JhLUmIkXKfcleO8fit9bPujzCoytSLUR6KnUHoOIjDyNxZAUVccJS0seqs+nlWOS4KU1uIx9zmQZajKokH5k4KB9F4zGFkrDqC5j2I79gBRca3xJWi6FUHOZteMEITgoywC1Wmdp/HrsNUXJXl/phFqjOg9KwpMztI4N6IMnpUZRBSpeSf8wmF88UFfpYJGw0YUyyLpn6ealgZvGCyOCbBdJ6POrs0fnH4Y8wbHyhiKxjQKZ2gbY5Onfwvhnsnum1WUSAm+ubA27OLQVV8PNydEItkMPstBTTmv+/c4QP5RhnwyRKQA2grDDuoSVKT2ksVL8qtLZ6fFrR5f/1TnCxLFiKX3xKtfIaJoV5O7lqA6ZoUTkNyIvjyywbw4 xfgbJIxg TTwpzy6xZ6WAt/1TWLYzpMVckWGmk0QSvTOxKRNEouKtlOiy5VU45rAdMAU4q0NhQvO65AKjkJF6cBsSmt0Jd5OK+05yQRtnmQGG0cWg3VJ0hVgdwdYznVULCt9XkJOiXFMyii0bwUAcDvqbGrQqL9J0DWDr9qKHjae7dEv5DMOakBaa+bL5HeTTCdFyMFS1hbOLSJIojwkneAbkZyld7+lMKkqK5KScT8b7FvYecZUJ+4bue/2tqIrLeqEGi8bGA8kcZoJI5xyv+5ZRddEm9uujXd3MDTe42nNYhuzrGzHNBxMUSECmJYK2YHjTzbre5OYA0uWqUfMqlPA/WrqxR0mM9OiYomF/jQLoNKCNh9qUjeQ/b46bCj6+2Nh/T87lQS4NY X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Check whether the starting address in the fault-around handler or the faulty address in the fault handler is part of a huge page in order to attempt a PMD sized PFN insertion into the VMA. 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 mount points 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 Signed-off-by: Loïc Molinari --- drivers/gpu/drm/drm_gem_shmem_helper.c | 57 +++++++++++++++++++++----- 1 file changed, 46 insertions(+), 11 deletions(-) diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c index e151262332f9..5d11bea573fe 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -580,6 +580,26 @@ static bool drm_gem_shmem_fault_is_valid(struct drm_gem_object *obj, return true; } +static bool drm_gem_shmem_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_map_pages(struct vm_fault *vmf, pgoff_t start_pgoff, pgoff_t end_pgoff) @@ -587,6 +607,7 @@ static vm_fault_t drm_gem_shmem_map_pages(struct vm_fault *vmf, struct vm_area_struct *vma = vmf->vma; struct drm_gem_object *obj = vma->vm_private_data; struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj); + struct page **pages = shmem->pages; unsigned long addr, pfn; vm_fault_t ret; @@ -598,15 +619,22 @@ static vm_fault_t drm_gem_shmem_map_pages(struct vm_fault *vmf, if (unlikely(!drm_gem_shmem_fault_is_valid(obj, start_pgoff))) { ret = VM_FAULT_SIGBUS; - } else { - /* Map a range of pages around the faulty address. */ - do { - pfn = page_to_pfn(shmem->pages[start_pgoff]); - ret = vmf_insert_pfn(vma, addr, pfn); - addr += PAGE_SIZE; - } while (++start_pgoff <= end_pgoff && ret == VM_FAULT_NOPAGE); + goto out; } + if (drm_gem_shmem_map_pmd(vmf, addr, pages[start_pgoff])) { + ret = VM_FAULT_NOPAGE; + goto out; + } + + /* Map a range of pages around the faulty address. */ + do { + pfn = page_to_pfn(pages[start_pgoff]); + ret = vmf_insert_pfn(vma, addr, pfn); + addr += PAGE_SIZE; + } while (++start_pgoff <= end_pgoff && ret == VM_FAULT_NOPAGE); + + out: dma_resv_unlock(shmem->base.resv); return ret; @@ -617,8 +645,9 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf) struct vm_area_struct *vma = vmf->vma; struct drm_gem_object *obj = vma->vm_private_data; struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj); - struct page *page; + struct page **pages = shmem->pages; pgoff_t page_offset; + unsigned long pfn; vm_fault_t ret; /* Offset to faulty address in the VMA (without the fake offset). */ @@ -628,12 +657,18 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf) if (unlikely(!drm_gem_shmem_fault_is_valid(obj, page_offset))) { 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_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