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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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable 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=3D' 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: Lo=C3=AFc 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_g= em_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, st= ruct drm_device *dev, } EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create); =20 -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 =3D vmf->vma; struct drm_gem_object *obj =3D 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_SUPPOR= TS_PUD_PFNMAP) + unsigned long paddr; +#endif =20 /* We don't use vmf->pgoff since that has the fake offset */ page_offset =3D (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 =3D VM_FAULT_SIGBUS; - } else { - page =3D shmem->pages[page_offset]; + goto out; + } =20 - ret =3D vmf_insert_pfn(vma, vmf->address, page_to_pfn(page)); + page =3D shmem->pages[page_offset]; + pfn =3D page_to_pfn(page); + + switch (order) { + case 0: + ret =3D vmf_insert_pfn(vma, vmf->address, pfn); + break; + +#ifdef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP + case PMD_ORDER: + paddr =3D pfn << PAGE_SHIFT; + if (((vmf->address & ~PMD_MASK) =3D=3D (paddr & ~PMD_MASK)) && + (folio_order(page_folio(page)) =3D=3D PMD_ORDER)) + ret =3D vmf_insert_pfn_pmd( + vmf, pfn & (PMD_MASK >> PAGE_SHIFT), false); + else + ret =3D VM_FAULT_FALLBACK; + break; +#endif + +#ifdef CONFIG_ARCH_SUPPORTS_PUD_PFNMAP + case PUD_ORDER: + paddr =3D pfn << PAGE_SHIFT; + if (((vmf->address & ~PUD_MASK) =3D=3D (paddr & ~PUD_MASK)) && + (folio_order(page_folio(page)) =3D=3D PUD_ORDER)) + ret =3D vmf_insert_pfn_pud( + vmf, pfn & (PUD_MASK >> PAGE_SHIFT), false); + else + ret =3D VM_FAULT_FALLBACK; + break; +#endif + + default: + ret =3D VM_FAULT_FALLBACK; + break; } =20 + out: dma_resv_unlock(shmem->base.resv); =20 return ret; } =20 +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 =3D vma->vm_private_data; @@ -639,6 +684,9 @@ static void drm_gem_shmem_vm_close(struct vm_area_struc= t *vma) =20 const struct vm_operations_struct drm_gem_shmem_vm_ops =3D { .fault =3D drm_gem_shmem_fault, +#if defined(CONFIG_ARCH_SUPPORTS_PMD_PFNMAP) || defined(CONFIG_ARCH_SUPPOR= TS_PUD_PFNMAP) + .huge_fault =3D drm_gem_shmem_huge_fault, +#endif .open =3D drm_gem_shmem_vm_open, .close =3D drm_gem_shmem_vm_close, }; --=20 2.47.3