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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 01B0417E0AC3; Mon, 29 Sep 2025 22:04:36 +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 Cc: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, linux-mm@kvack.org, kernel@collabora.com Subject: [PATCH 1/8] drm/shmem-helper: Add huge page fault handler Date: Mon, 29 Sep 2025 22:03:09 +0200 Message-ID: <20250929200316.18417-2-loic.molinari@collabora.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20250929200316.18417-1-loic.molinari@collabora.com> References: <20250929200316.18417-1-loic.molinari@collabora.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 3F98540007 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: fyoqe88b9ypp41re1facb73oc1a6u85x X-HE-Tag: 1759176280-309232 X-HE-Meta: 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 pkSgUnMI 31FgShEk77DhIEKMSoIHlWO1gRbNqc06r2RYqjBAIUG47jy1r0EU4ktq8uCYaaXKRILglAHp1p5ok/5AIgioP1XtParZTK2Ia7R5KHwAFVXGM/pkbcriswuN3TgR/CbSm0PjxQn7JzueE7xI7gVoq7so5kMEc0qcD41/+NlYdoowsU+1tDWBHBi453kT94zuJkycRRbOybNhES152TXs9EJ4vwblJzZCispDommhD0HxAhKjNwDBbPf2jwekx5g6UsyiHHMPUNeE9TY5Eg/YW0YAKkK3P+jRH1UD0HuTCsfWMRE3+sYt6k1ymvGpLkBNWBvwx6uGcfTqcdfm5yz0UUKc+0uZSyVsESALaKT42+q23qWDvuwIjcNLdNGc4F8aCc2k9 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: This gives the mm subsystem the ability to propose the insertion of PUD or PMD-sized mappings for the faulting addresses. On builds with CONFIG_TRANSPARENT_HUGEPAGE enabled, if the mmap() user address is aligned to a huge page size, 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, the CPU mapping will 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. v2: - set ret to VM_FAULT_FALLBACK in default switch statement - ifdef out paddr declaration - improve commit message Signed-off-by: Loïc Molinari Reviewed-by: Boris Brezillon --- drivers/gpu/drm/drm_gem_shmem_helper.c | 56 ++++++++++++++++++++++++-- 1 file changed, 52 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c index 50594cf8e17c..22c4b09e10a3 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -573,7 +573,8 @@ int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev, } EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create); -static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf) +static vm_fault_t drm_gem_shmem_huge_fault(struct vm_fault *vmf, + unsigned int order) { struct vm_area_struct *vma = vmf->vma; struct drm_gem_object *obj = vma->vm_private_data; @@ -582,6 +583,10 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf) vm_fault_t ret; struct page *page; pgoff_t page_offset; + unsigned long pfn; +#if defined(CONFIG_ARCH_SUPPORTS_PMD_PFNMAP) || defined(CONFIG_ARCH_SUPPORTS_PUD_PFNMAP) + unsigned long paddr; +#endif /* We don't use vmf->pgoff since that has the fake offset */ page_offset = (vmf->address - vma->vm_start) >> PAGE_SHIFT; @@ -592,17 +597,57 @@ 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)); + page = shmem->pages[page_offset]; + pfn = page_to_pfn(page); + + switch (order) { + case 0: + ret = vmf_insert_pfn(vma, vmf->address, pfn); + break; + +#ifdef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP + case PMD_ORDER: + paddr = pfn << PAGE_SHIFT; + if (((vmf->address & ~PMD_MASK) == (paddr & ~PMD_MASK)) && + (folio_order(page_folio(page)) == PMD_ORDER)) + ret = vmf_insert_pfn_pmd( + vmf, pfn & (PMD_MASK >> PAGE_SHIFT), false); + else + ret = VM_FAULT_FALLBACK; + break; +#endif + +#ifdef CONFIG_ARCH_SUPPORTS_PUD_PFNMAP + case PUD_ORDER: + paddr = pfn << PAGE_SHIFT; + if (((vmf->address & ~PUD_MASK) == (paddr & ~PUD_MASK)) && + (folio_order(page_folio(page)) == PUD_ORDER)) + ret = vmf_insert_pfn_pud( + vmf, pfn & (PUD_MASK >> PAGE_SHIFT), false); + else + ret = VM_FAULT_FALLBACK; + break; +#endif + + default: + ret = VM_FAULT_FALLBACK; + break; } + out: dma_resv_unlock(shmem->base.resv); return ret; } +static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf) +{ + return drm_gem_shmem_huge_fault(vmf, 0); +} + static void drm_gem_shmem_vm_open(struct vm_area_struct *vma) { struct drm_gem_object *obj = vma->vm_private_data; @@ -639,6 +684,9 @@ static void drm_gem_shmem_vm_close(struct vm_area_struct *vma) const struct vm_operations_struct drm_gem_shmem_vm_ops = { .fault = drm_gem_shmem_fault, +#if defined(CONFIG_ARCH_SUPPORTS_PMD_PFNMAP) || defined(CONFIG_ARCH_SUPPORTS_PUD_PFNMAP) + .huge_fault = drm_gem_shmem_huge_fault, +#endif .open = drm_gem_shmem_vm_open, .close = drm_gem_shmem_vm_close, }; -- 2.47.3