From nobody Mon Apr 6 13:29:14 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BC8653F54C4; Thu, 19 Mar 2026 18:24:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773944642; cv=none; b=XCLZ/wW57WMJHtLWHyOGoYBHENKqpUE92UMIDQtjEjBwm2SEuWD5nkhod//hAEc4DFrLMlYwHZ8N3VpQbzp+fI0IfHFK3SzEt4pUnTqn0M52synoP77SC9RBmqoYQ4nf1vLKXgzNPg6DNpyEMxFsVesP35KmrRAEBRxbw4LJFmI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773944642; c=relaxed/simple; bh=6Gs389cDcfbWp+CxLW+X4AJWAHdnJe2WbDq0Ac8c1Ks=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=DKDeWshKQZVoSHNnQ4hdZo6GWXLsvKfxP9MjJ8LlJ+IQLA6X2uThRdNf2+zYi2cqfzCvP3jZbtHni4AJbyKyKEdbtPYdwCdZp2FqskurG2E2Og8KA9mTRP98IdpqHtZikDF/sezKd3WrWeOsTQsTfE66XdqXW/6z0cy19iHYFqw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PUlhN8ha; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="PUlhN8ha" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 10260C19424; Thu, 19 Mar 2026 18:24:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773944642; bh=6Gs389cDcfbWp+CxLW+X4AJWAHdnJe2WbDq0Ac8c1Ks=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PUlhN8haks8iHpDvH0wIqg5gSdCrrEldNyOlgD9TsNyj0dXbYG6fnWoWpEQUFWx5q rTg1zx8L0sjbLEazEVdBi75GgyRFBkBC/PQzEl0CH9VAX0X/HeLOi28lekyh4tHlHL yuuNnNAEv1380wGAIGx5hEKAO+j9nXu9ijB5DcWoplNfM+EvpT/cTrZb222pK+KhBD sH7f+F/tco8dLn58XHzoh2T+tXJPX17exc73Ql4kyWYH7IKG89vuFHwbo1UQdXVEmk 22QXHLGub2U1S3Qa+c31qYqQwJohwzKf9NScIGmL9qFhYUaRju6YRw+2gcVSMSbXqp tHS2OmWhECtEw== From: "Lorenzo Stoakes (Oracle)" To: Andrew Morton Cc: Jonathan Corbet , Clemens Ladisch , Arnd Bergmann , Greg Kroah-Hartman , "K . Y . Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li , Alexander Shishkin , Maxime Coquelin , Alexandre Torgue , Miquel Raynal , Richard Weinberger , Vignesh Raghavendra , Bodo Stroesser , "Martin K . Petersen" , David Howells , Marc Dionne , Alexander Viro , Christian Brauner , Jan Kara , David Hildenbrand , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-mtd@lists.infradead.org, linux-staging@lists.linux.dev, linux-scsi@vger.kernel.org, target-devel@vger.kernel.org, linux-afs@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Ryan Roberts Subject: [PATCH v3 06/16] mm: add mmap_action_simple_ioremap() Date: Thu, 19 Mar 2026 18:23:30 +0000 Message-ID: X-Mailer: git-send-email 2.53.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Currently drivers use vm_iomap_memory() as a simple helper function for I/O remapping memory over a range starting at a specified physical address over a specified length. In order to utilise this from mmap_prepare, separate out the core logic into __simple_ioremap_prep(), update vm_iomap_memory() to use it, and add simple_ioremap_prepare() to do the same with a VMA descriptor object. We also add MMAP_SIMPLE_IO_REMAP and relevant fields to the struct mmap_action type to permit this operation also. We use mmap_action_ioremap() to set up the actual I/O remap operation once we have checked and figured out the parameters, which makes simple_ioremap_prepare() easy to implement. We then add mmap_action_simple_ioremap() to allow drivers to make use of this mode. We update the mmap_prepare documentation to describe this mode. Finally, we update the VMA tests to reflect this change. Reviewed-by: Suren Baghdasaryan Signed-off-by: Lorenzo Stoakes (Oracle) --- Documentation/filesystems/mmap_prepare.rst | 3 + include/linux/mm.h | 24 +++++- include/linux/mm_types.h | 6 +- mm/internal.h | 1 + mm/memory.c | 85 +++++++++++++++------- mm/util.c | 5 ++ tools/testing/vma/include/dup.h | 6 +- 7 files changed, 102 insertions(+), 28 deletions(-) diff --git a/Documentation/filesystems/mmap_prepare.rst b/Documentation/fil= esystems/mmap_prepare.rst index 20db474915da..be76ae475b9c 100644 --- a/Documentation/filesystems/mmap_prepare.rst +++ b/Documentation/filesystems/mmap_prepare.rst @@ -153,5 +153,8 @@ pointer. These are: * mmap_action_ioremap_full() - Same as mmap_action_ioremap(), only remaps the entire mapping from ``start_pfn`` onward. =20 +* mmap_action_simple_ioremap() - Sets up an I/O remap from a specified + physical address and over a specified length. + **NOTE:** The ``action`` field should never normally be manipulated direct= ly, rather you ought to use one of these helpers. diff --git a/include/linux/mm.h b/include/linux/mm.h index 68dee1101313..ef2e4dccfe8e 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -4337,11 +4337,33 @@ static inline void mmap_action_ioremap(struct vm_ar= ea_desc *desc, * @start_pfn: The first PFN in the range to remap. */ static inline void mmap_action_ioremap_full(struct vm_area_desc *desc, - unsigned long start_pfn) + unsigned long start_pfn) { mmap_action_ioremap(desc, desc->start, start_pfn, vma_desc_size(desc)); } =20 +/** + * mmap_action_simple_ioremap - helper for mmap_prepare hook to specify th= at the + * physical range in [start_phys_addr, start_phys_addr + size) should be I= /O + * remapped. + * @desc: The VMA descriptor for the VMA requiring remap. + * @start_phys_addr: Start of the physical memory to be mapped. + * @size: Size of the area to map. + * + * NOTE: Some drivers might want to tweak desc->page_prot for purposes of + * write-combine or similar. + */ +static inline void mmap_action_simple_ioremap(struct vm_area_desc *desc, + phys_addr_t start_phys_addr, + unsigned long size) +{ + struct mmap_action *action =3D &desc->action; + + action->simple_ioremap.start_phys_addr =3D start_phys_addr; + action->simple_ioremap.size =3D size; + action->type =3D MMAP_SIMPLE_IO_REMAP; +} + int mmap_action_prepare(struct vm_area_desc *desc); int mmap_action_complete(struct vm_area_struct *vma, struct mmap_action *action, diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 4a229cc0a06b..50685cf29792 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -814,6 +814,7 @@ enum mmap_action_type { MMAP_NOTHING, /* Mapping is complete, no further action. */ MMAP_REMAP_PFN, /* Remap PFN range. */ MMAP_IO_REMAP_PFN, /* I/O remap PFN range. */ + MMAP_SIMPLE_IO_REMAP, /* I/O remap with guardrails. */ }; =20 /* @@ -822,13 +823,16 @@ enum mmap_action_type { */ struct mmap_action { union { - /* Remap range. */ struct { unsigned long start; unsigned long start_pfn; unsigned long size; pgprot_t pgprot; } remap; + struct { + phys_addr_t start_phys_addr; + unsigned long size; + } simple_ioremap; }; enum mmap_action_type type; =20 diff --git a/mm/internal.h b/mm/internal.h index e0f554178143..2aa04d87ac10 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -1804,6 +1804,7 @@ int dup_mmap(struct mm_struct *mm, struct mm_struct *= oldmm); int remap_pfn_range_prepare(struct vm_area_desc *desc); int remap_pfn_range_complete(struct vm_area_struct *vma, struct mmap_action *action); +int simple_ioremap_prepare(struct vm_area_desc *desc); =20 static inline int io_remap_pfn_range_prepare(struct vm_area_desc *desc) { diff --git a/mm/memory.c b/mm/memory.c index 9dec67a18116..b3bcc21af20a 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3170,6 +3170,58 @@ int remap_pfn_range_complete(struct vm_area_struct *= vma, return do_remap_pfn_range(vma, start, pfn, size, prot); } =20 +static int __simple_ioremap_prep(unsigned long vm_len, pgoff_t vm_pgoff, + phys_addr_t start_phys, unsigned long size, + unsigned long *pfnp) +{ + unsigned long pfn, pages; + + /* Check that the physical memory area passed in looks valid */ + if (start_phys + size < start_phys) + return -EINVAL; + /* + * You *really* shouldn't map things that aren't page-aligned, + * but we've historically allowed it because IO memory might + * just have smaller alignment. + */ + size +=3D start_phys & ~PAGE_MASK; + pfn =3D start_phys >> PAGE_SHIFT; + pages =3D (size + ~PAGE_MASK) >> PAGE_SHIFT; + if (pfn + pages < pfn) + return -EINVAL; + + /* We start the mapping 'vm_pgoff' pages into the area */ + if (vm_pgoff > pages) + return -EINVAL; + pfn +=3D vm_pgoff; + pages -=3D vm_pgoff; + + /* Can we fit all of the mapping? */ + if ((vm_len >> PAGE_SHIFT) > pages) + return -EINVAL; + + *pfnp =3D pfn; + return 0; +} + +int simple_ioremap_prepare(struct vm_area_desc *desc) +{ + struct mmap_action *action =3D &desc->action; + const phys_addr_t start =3D action->simple_ioremap.start_phys_addr; + const unsigned long size =3D action->simple_ioremap.size; + unsigned long pfn; + int err; + + err =3D __simple_ioremap_prep(vma_desc_size(desc), desc->pgoff, + start, size, &pfn); + if (err) + return err; + + /* The I/O remap logic does the heavy lifting. */ + mmap_action_ioremap_full(desc, pfn); + return io_remap_pfn_range_prepare(desc); +} + /** * vm_iomap_memory - remap memory to userspace * @vma: user vma to map to @@ -3187,32 +3239,15 @@ int remap_pfn_range_complete(struct vm_area_struct = *vma, */ int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigne= d long len) { - unsigned long vm_len, pfn, pages; - - /* Check that the physical memory area passed in looks valid */ - if (start + len < start) - return -EINVAL; - /* - * You *really* shouldn't map things that aren't page-aligned, - * but we've historically allowed it because IO memory might - * just have smaller alignment. - */ - len +=3D start & ~PAGE_MASK; - pfn =3D start >> PAGE_SHIFT; - pages =3D (len + ~PAGE_MASK) >> PAGE_SHIFT; - if (pfn + pages < pfn) - return -EINVAL; - - /* We start the mapping 'vm_pgoff' pages into the area */ - if (vma->vm_pgoff > pages) - return -EINVAL; - pfn +=3D vma->vm_pgoff; - pages -=3D vma->vm_pgoff; + const unsigned long vm_start =3D vma->vm_start; + const unsigned long vm_end =3D vma->vm_end; + const unsigned long vm_len =3D vm_end - vm_start; + unsigned long pfn; + int err; =20 - /* Can we fit all of the mapping? */ - vm_len =3D vma->vm_end - vma->vm_start; - if (vm_len >> PAGE_SHIFT > pages) - return -EINVAL; + err =3D __simple_ioremap_prep(vm_len, vma->vm_pgoff, start, len, &pfn); + if (err) + return err; =20 /* Ok, let it rip */ return io_remap_pfn_range(vma, vma->vm_start, pfn, vm_len, vma->vm_page_p= rot); diff --git a/mm/util.c b/mm/util.c index fc1bd8a8f3ea..879ba62b5f0c 100644 --- a/mm/util.c +++ b/mm/util.c @@ -1392,6 +1392,8 @@ int mmap_action_prepare(struct vm_area_desc *desc) return remap_pfn_range_prepare(desc); case MMAP_IO_REMAP_PFN: return io_remap_pfn_range_prepare(desc); + case MMAP_SIMPLE_IO_REMAP: + return simple_ioremap_prepare(desc); } =20 WARN_ON_ONCE(1); @@ -1423,6 +1425,7 @@ int mmap_action_complete(struct vm_area_struct *vma, err =3D remap_pfn_range_complete(vma, action); break; case MMAP_IO_REMAP_PFN: + case MMAP_SIMPLE_IO_REMAP: /* Should have been delegated. */ WARN_ON_ONCE(1); err =3D -EINVAL; @@ -1441,6 +1444,7 @@ int mmap_action_prepare(struct vm_area_desc *desc) break; case MMAP_REMAP_PFN: case MMAP_IO_REMAP_PFN: + case MMAP_SIMPLE_IO_REMAP: WARN_ON_ONCE(1); /* nommu cannot handle these. */ break; } @@ -1460,6 +1464,7 @@ int mmap_action_complete(struct vm_area_struct *vma, break; case MMAP_REMAP_PFN: case MMAP_IO_REMAP_PFN: + case MMAP_SIMPLE_IO_REMAP: WARN_ON_ONCE(1); /* nommu cannot handle this. */ =20 err =3D -EINVAL; diff --git a/tools/testing/vma/include/dup.h b/tools/testing/vma/include/du= p.h index aa34966cbc62..1b86c34e1158 100644 --- a/tools/testing/vma/include/dup.h +++ b/tools/testing/vma/include/dup.h @@ -453,6 +453,7 @@ enum mmap_action_type { MMAP_NOTHING, /* Mapping is complete, no further action. */ MMAP_REMAP_PFN, /* Remap PFN range. */ MMAP_IO_REMAP_PFN, /* I/O remap PFN range. */ + MMAP_SIMPLE_IO_REMAP, /* I/O remap with guardrails. */ }; =20 /* @@ -461,13 +462,16 @@ enum mmap_action_type { */ struct mmap_action { union { - /* Remap range. */ struct { unsigned long start; unsigned long start_pfn; unsigned long size; pgprot_t pgprot; } remap; + struct { + phys_addr_t start_phys_addr; + unsigned long size; + } simple_ioremap; }; enum mmap_action_type type; =20 --=20 2.53.0