From mboxrd@z Thu Jan 1 00:00:00 1970 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 3EC221F192E; Wed, 18 Mar 2026 20:39:37 +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=1773866377; cv=none; b=ROJzl/nnlsMhyYq8OA7WZGskZLFALnXGCu98PGnrGlmYChyfwaUeuduD/wU1d0Osrq0pWTMmmnsNsumcKOaUCDRxE5LAZZYn8tmUZ3fmyJFUPrvW/20ac437vlsgw/rJnWfaBNbEPP1PZQ2cPR7ExV+PDbyLJitljvRHvqeULCI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773866377; c=relaxed/simple; bh=ko4orCFKsaEPvSaBxnt5g878sJgcfWQEheBNrNLKEMQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=pejHhklYbwDFhobM8mv8AiAEZFTeRaRCLRgGP8Lt0OCHUR0CsL40713GPe8k5E1ggBBfsoHDPrTyfuH4s+KiiTUF9Me6KcaU00kc/qgRNt6G8BcJbMRNEd2a7ddDRnRjjtHqzjIo9cuMo/tdXK5fshO/HhEp3rPtlQTO+/E4fo0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=E47VA4ey; 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="E47VA4ey" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7479EC19424; Wed, 18 Mar 2026 20:39:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773866376; bh=ko4orCFKsaEPvSaBxnt5g878sJgcfWQEheBNrNLKEMQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=E47VA4eyxbQXzd9/UHnJc4CUyaJrHozBi4afZf6c2jVcv2hd+Z0m+zIqpNy1M8pcj w9oXKVlXsLe1VI72kOIoJ7l6ut2RfKSHB1X8nGTrbocnlF7Eed4LpFpwhujoluz0ah A2YQHuP+2I42ZaCouQNufu5wxVSBwJIHljGN7Mpuwkfmno/V0udnRXB25cKn2Fu76k Bj63OdwEfHZJK2feU7hXM5AaBG8wRBm9rVwUfTJFLT5MH/nlGD/sZWJpPDFTJMmEYQ nIrm5s3/krtA3DDEiPdP/tIOsTj2jTMHTs15YMbXC5SKfl8L20fd17zraYnMf17hnN qalFYxNmTkB4w== Date: Wed, 18 Mar 2026 20:39:25 +0000 From: "Lorenzo Stoakes (Oracle)" To: Suren Baghdasaryan Cc: Andrew Morton , 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 , 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: Re: [PATCH v2 06/16] mm: add mmap_action_simple_ioremap() Message-ID: <330f3614-7dc1-4e80-96c4-8472b25108bb@lucifer.local> References: <1e58aaf3cdb61cc317d890c12c9a558dfc206913.1773695307.git.ljs@kernel.org> 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-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Mon, Mar 16, 2026 at 09:14:28PM -0700, Suren Baghdasaryan wrote: > On Mon, Mar 16, 2026 at 2:13 PM Lorenzo Stoakes (Oracle) wrote: > > > > 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. > > > > Signed-off-by: Lorenzo Stoakes (Oracle) > > A couple of nits, but otherwise LGTM. > > Reviewed-by: Suren Baghdasaryan Thanks! > > > --- > > Documentation/filesystems/mmap_prepare.rst | 3 + > > include/linux/mm.h | 24 +++++- > > include/linux/mm_types.h | 6 +- > > mm/internal.h | 2 + > > mm/memory.c | 87 +++++++++++++++------- > > mm/util.c | 12 +++ > > tools/testing/vma/include/dup.h | 6 +- > > 7 files changed, 112 insertions(+), 28 deletions(-) > > > > diff --git a/Documentation/filesystems/mmap_prepare.rst b/Documentation/filesystems/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. > > > > +* 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 directly, > > rather you ought to use one of these helpers. > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > index ad1b8c3c0cfd..df8fa6e6402b 100644 > > --- a/include/linux/mm.h > > +++ b/include/linux/mm.h > > @@ -4337,11 +4337,33 @@ static inline void mmap_action_ioremap(struct vm_area_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)); > > } > > > > +/** > > + * mmap_action_simple_ioremap - helper for mmap_prepare hook to specify that 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 = &desc->action; > > + > > + action->simple_ioremap.start_phys_addr = start_phys_addr; > > + action->simple_ioremap.size = size; > > + action->type = 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. */ > > }; > > > > /* > > @@ -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; > > > > diff --git a/mm/internal.h b/mm/internal.h > > index f5774892071e..0eaca2f0eb6a 100644 > > --- a/mm/internal.h > > +++ b/mm/internal.h > > @@ -1804,6 +1804,8 @@ 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); > > +/* No simple_ioremap_complete, is ultimately handled by remap complete. */ > > > > 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..f3f4046aee97 100644 > > --- a/mm/memory.c > > +++ b/mm/memory.c > > @@ -3170,6 +3170,59 @@ int remap_pfn_range_complete(struct vm_area_struct *vma, > > return do_remap_pfn_range(vma, start, pfn, size, prot); > > } > > > > +static int __simple_ioremap_prep(unsigned long vm_start, unsigned long vm_end, > > nit: vm_start and vm_end are used only to calculate vm_len. You could > reduce the number of arguments by just passing vm_len. Ack will fixup! > > > + pgoff_t vm_pgoff, phys_addr_t start_phys, > > + unsigned long size, unsigned long *pfnp) > > +{ > > + const unsigned long vm_len = vm_end - vm_start; > > + 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 += start_phys & ~PAGE_MASK; > > + pfn = start_phys >> PAGE_SHIFT; > > + pages = (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 += vm_pgoff; > > + pages -= vm_pgoff; > > + > > + /* Can we fit all of the mapping? */ > > + if ((vm_len >> PAGE_SHIFT) > pages) > > + return -EINVAL; > > + > > + *pfnp = pfn; > > + return 0; > > +} > > + > > +int simple_ioremap_prepare(struct vm_area_desc *desc) > > +{ > > + struct mmap_action *action = &desc->action; > > + const phys_addr_t start = action->simple_ioremap.start_phys_addr; > > + const unsigned long size = action->simple_ioremap.size; > > + unsigned long pfn; > > + int err; > > + > > + err = __simple_ioremap_prep(desc->start, desc->end, desc->pgoff, > > + start, size, &pfn); > > + if (err) > > + return err; > > + > > + /* The I/O remap logic does the heavy lifting. */ > > + mmap_action_ioremap(desc, desc->start, pfn, vma_desc_size(desc)); > > nit: Looks like a perfect opportunity to use mmap_action_ioremap_full() here. Yeah can do! > > > + return mmap_action_prepare(desc); > > Ok, so IIUC this uses recursion: > mmap_action_prepare(MMAP_SIMPLE_IO_REMAP) -> simple_ioremap_prepare() > -> mmap_action_prepare(MMAP_IO_REMAP_PFN). Yep, it's one level, I think that should be ok? :) > > > +} > > + > > /** > > * vm_iomap_memory - remap memory to userspace > > * @vma: user vma to map to > > @@ -3187,32 +3240,16 @@ int remap_pfn_range_complete(struct vm_area_struct *vma, > > */ > > int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned 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 += start & ~PAGE_MASK; > > - pfn = start >> PAGE_SHIFT; > > - pages = (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 += vma->vm_pgoff; > > - pages -= vma->vm_pgoff; > > + const unsigned long vm_start = vma->vm_start; > > + const unsigned long vm_end = vma->vm_end; > > + const unsigned long vm_len = vm_end - vm_start; > > + unsigned long pfn; > > + int err; > > > > - /* Can we fit all of the mapping? */ > > - vm_len = vma->vm_end - vma->vm_start; > > - if (vm_len >> PAGE_SHIFT > pages) > > - return -EINVAL; > > + err = __simple_ioremap_prep(vm_start, vm_end, vma->vm_pgoff, start, > > + len, &pfn); > > + if (err) > > + return err; > > > > /* Ok, let it rip */ > > return io_remap_pfn_range(vma, vma->vm_start, pfn, vm_len, vma->vm_page_prot); > > diff --git a/mm/util.c b/mm/util.c > > index cdfba09e50d7..aa92e471afe1 100644 > > --- a/mm/util.c > > +++ b/mm/util.c > > @@ -1390,6 +1390,8 @@ 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); > > } > > > > WARN_ON_ONCE(1); > > @@ -1421,6 +1423,14 @@ int mmap_action_complete(struct vm_area_struct *vma, > > case MMAP_IO_REMAP_PFN: > > err = io_remap_pfn_range_complete(vma, action); > > break; > > + case MMAP_SIMPLE_IO_REMAP: > > + /* > > + * The simple I/O remap should have been delegated to an I/O > > + * remap. > > + */ > > + WARN_ON_ONCE(1); > > + err = -EINVAL; > > + break; > > } > > > > return mmap_action_finish(vma, action, err); > > @@ -1434,6 +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; > > } > > @@ -1452,6 +1463,7 @@ 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. */ > > > > err = -EINVAL; > > diff --git a/tools/testing/vma/include/dup.h b/tools/testing/vma/include/dup.h > > index 4570ec77f153..114daaef4f73 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. */ > > }; > >> > /* > > @@ -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; > > + unsigned long len; > > + } simple_ioremap; > > }; > > enum mmap_action_type type; > > > > -- > > 2.53.0 > > Cheers, Lorenzo