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Fri, 10 Jul 2026 09:39:08 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1wiEFo-00000007YRj-1Qzt; Fri, 10 Jul 2026 13:39:08 -0300 Date: Fri, 10 Jul 2026 13:39:08 -0300 From: Jason Gunthorpe To: Stanislav Kinsburskii Cc: airlied@gmail.com, akhilesh@ee.iitb.ac.in, akpm@linux-foundation.org, corbet@lwn.net, dakr@kernel.org, david@kernel.org, decui@microsoft.com, haiyangz@microsoft.com, kees@kernel.org, kys@microsoft.com, leon@kernel.org, liam@infradead.org, lizhi.hou@amd.com, ljs@kernel.org, longli@microsoft.com, lyude@redhat.com, maarten.lankhorst@linux.intel.com, mamin506@gmail.com, mhocko@suse.com, mripard@kernel.org, nouveau@lists.freedesktop.org, ogabbay@kernel.org, oleg@redhat.com, rppt@kernel.org, shuah@kernel.org, simona@ffwll.ch, skhan@linuxfoundation.org, surenb@google.com, tzimmermann@suse.de, vbabka@kernel.org, wei.liu@kernel.org, dri-devel@lists.freedesktop.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-rdma@vger.kernel.org Subject: Re: [PATCH v7 4/8] mshv: Use hmm_range_fault_unlocked_timeout() for region faults Message-ID: <20260710163908.GS118978@ziepe.ca> References: <178345345668.660027.2952911919681614557.stgit@skinsburskii> <178345363584.660027.14063544694872741718.stgit@skinsburskii> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <178345363584.660027.14063544694872741718.stgit@skinsburskii> X-Rspamd-Queue-Id: 7A23512000A X-Rspam-User: X-Stat-Signature: ys96oz6gy6updiyiuz5m9xmdek5hdmrg X-Rspamd-Server: rspam03 X-HE-Tag: 1783701550-783875 X-HE-Meta: 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 pAI+xQOS +uCE+r1Z1fwsKv0Fb7OVX9mf33Wd7RPHd9vhIbgTi3mIKMbvg/QTZPGPdAOTbF5ce6zr+pK6HFDL9haPMP74Jct72hUYZ1NwuP+20UY1UVof4eAhNYf7RYwkQN3XwA19uUOsNN3ynG8hKMB6LHT/j77I3U//5TL+DMJND8cqObqq6pa/qd+6xNnu1+v2cyuB4kN9DQ4ei07Vpx9RpXmGMhlCMP14Xfs2FG/cxBO+TfDOmw6lf0C2chJ/lVRUTJlKv9La4GvKuLy+5eOM2HSisDJTzYMmzls/T5qPt7AghPZyrs9mQxFoBw2pgChakDMECgtDa7DFdYtsuNA67Uu9gw6hqzD+Zd72tKlTbjKBQ5Hhx0kj6+kfWPHS56/NYgp7W8XXu Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jul 07, 2026 at 12:47:15PM -0700, Stanislav Kinsburskii wrote: > MSHV currently faults movable memory regions by taking mmap_read_lock() > around hmm_range_fault(). That prevents the fault path from handling VMAs > whose fault handlers need to drop mmap_lock, such as userfaultfd-backed > mappings. > > Use hmm_range_fault_unlocked_timeout() instead. Passing a timeout of 0 > preserves MSHV's existing unbounded retry behavior while letting the HMM > helper own mmap_lock acquisition and refresh range->notifier_seq internally > before walking the range. After the fault succeeds, MSHV still takes > mreg_mutex and checks mmu_interval_read_retry() before installing the pages > into the region, so the existing invalidation synchronization is preserved. > > Fold the small fault-and-lock helper into mshv_region_range_fault(), since > the remaining retry path is just the standard "fault, take the driver lock, > check the interval notifier sequence" pattern. > > Signed-off-by: Stanislav Kinsburskii > --- > drivers/hv/mshv_regions.c | 54 ++++++++------------------------------------- > 1 file changed, 10 insertions(+), 44 deletions(-) Reviewed-by: Jason Gunthorpe Jason