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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: Re: [PATCH v3 15/16] mm: add mmap_action_map_kernel_pages[_full]() Message-ID: References: <54ff3670662e10a66ce0c1a13c0ae93b99a5f201.1773944114.git.ljs@kernel.org> <20260320210812.GA3988975@ax162> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260320210812.GA3988975@ax162> X-Stat-Signature: khmh6awwkiy9srgf95tdr3uxwhobu893 X-Rspamd-Server: rspam09 X-Rspam-User: X-Rspamd-Queue-Id: EAF171C0003 X-HE-Tag: 1774044866-16102 X-HE-Meta: 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 YRXCoqVh W9l4AwPASwS2v1RYxlcK4j0hNNdTHi1z9Di7sT6WyksbLvWoJ4zZhsdXRFRral5gWQs0uKbo2o+8sqYh2lo++GkyZ5Rf8XwXC0U1QXb0c76ma+E8qVWLrqp0TLpziMzFSvHpVCIyH1Zvfj9huppCY9VzAW0ywAY4aIwObEkRvyfIFBfKYW4ziYQT1hOLkXf97XW83xpP30Gr4doH/SDrj0GIcST5Whu3s2zwe9sC2FeLPBLdACUCEEkiBKFHQM6WeesCG5Y923SfCg2+5HDE1A5gElJDnARyQ11H1IyHlfpb4mfleXyECMP4m0e5UAI+1E+ZxK2b7mV2kfBgSKAG487Hi2jxrzB4xA/BtELx3EewmGFmU0uNfpJUQLYWFtligac9M Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Mar 20, 2026 at 02:08:12PM -0700, Nathan Chancellor wrote: > Hi Lorenzo, > > On Thu, Mar 19, 2026 at 06:23:39PM +0000, Lorenzo Stoakes (Oracle) wrote: > > A user can invoke mmap_action_map_kernel_pages() to specify that the > > mapping should map kernel pages starting from desc->start of a specified > > number of pages specified in an array. > > > > In order to implement this, adjust mmap_action_prepare() to be able to > > return an error code, as it makes sense to assert that the specified > > parameters are valid as quickly as possible as well as updating the VMA > > flags to include VMA_MIXEDMAP_BIT as necessary. > > > > This provides an mmap_prepare equivalent of vm_insert_pages(). We > > additionally update the existing vm_insert_pages() code to use > > range_in_vma() and add a new range_in_vma_desc() helper function for the > > mmap_prepare case, sharing the code between the two in range_is_subset(). > > > > We add both mmap_action_map_kernel_pages() and > > mmap_action_map_kernel_pages_full() to allow for both partial and full VMA > > mappings. > > > > We update the documentation to reflect the new features. > > > > Finally, we update the VMA tests accordingly to reflect the changes. > > > > Reviewed-by: Suren Baghdasaryan > > Signed-off-by: Lorenzo Stoakes (Oracle) > ... > > diff --git a/mm/util.c b/mm/util.c > > index 8cf59267a9ac..682d0d24e1c6 100644 > > --- a/mm/util.c > > +++ b/mm/util.c > > @@ -1446,6 +1446,8 @@ int mmap_action_prepare(struct vm_area_desc *desc) > > return io_remap_pfn_range_prepare(desc); > > case MMAP_SIMPLE_IO_REMAP: > > return simple_ioremap_prepare(desc); > > + case MMAP_MAP_KERNEL_PAGES: > > + return map_kernel_pages_prepare(desc); > > } > > > > WARN_ON_ONCE(1); > > @@ -1476,6 +1478,9 @@ int mmap_action_complete(struct vm_area_struct *vma, > > case MMAP_REMAP_PFN: > > err = remap_pfn_range_complete(vma, action); > > break; > > + case MMAP_MAP_KERNEL_PAGES: > > + err = map_kernel_pages_complete(vma, action); > > + break; > > case MMAP_IO_REMAP_PFN: > > case MMAP_SIMPLE_IO_REMAP: > > /* Should have been delegated. */ > > @@ -1497,6 +1502,7 @@ int mmap_action_prepare(struct vm_area_desc *desc) > > case MMAP_REMAP_PFN: > > case MMAP_IO_REMAP_PFN: > > case MMAP_SIMPLE_IO_REMAP: > > + case MMAP_MAP_KERNEL_PAGES: > > WARN_ON_ONCE(1); /* nommu cannot handle these. */ > > break; > > } > > Not sure if it has been reported/addressed yet but it looks like > mmap_action_complete() was missed here, as pointed out by clang: > > $ make -skj"$(nproc)" ARCH=arm LLVM=1 mrproper allnoconfig mm/util.o > mm/util.c:1520:10: warning: enumeration value 'MMAP_MAP_KERNEL_PAGES' not handled in switch [-Wswitch] > 1520 | switch (action->type) { > | ^~~~~~~~~~~~ > > I assume > > diff --git a/mm/util.c b/mm/util.c > index 682d0d24e1c6..c41c119a5a74 100644 > --- a/mm/util.c > +++ b/mm/util.c > @@ -1523,6 +1523,7 @@ int mmap_action_complete(struct vm_area_struct *vma, > case MMAP_REMAP_PFN: > case MMAP_IO_REMAP_PFN: > case MMAP_SIMPLE_IO_REMAP: > + case MMAP_MAP_KERNEL_PAGES: > WARN_ON_ONCE(1); /* nommu cannot handle this. */ > > err = -EINVAL; > -- > > should be the fix? > > Cheers, > Nathan Thanks, will fix, working on a respin now anyway :) Cheers, Lorenzo