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[2001:1ae9:1c2:4c00:20f:c6b4:1e57:7965]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a5a17894d40sm1790774566b.75.2024.05.22.09.56.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 May 2024 09:56:30 -0700 (PDT) Date: Wed, 22 May 2024 18:56:29 +0200 From: Andrew Jones To: Yan Zhao Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, alex.williamson@redhat.com, kevin.tian@intel.com, jgg@nvidia.com, yishaih@nvidia.com, shameerali.kolothum.thodi@huawei.com Subject: Re: [PATCH] vfio/pci: take mmap write lock for io_remap_pfn_range Message-ID: <20240522-b1ef260c9d6944362c14c246@orel> References: <20230508125842.28193-1-yan.y.zhao@intel.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=us-ascii Content-Disposition: inline In-Reply-To: <20230508125842.28193-1-yan.y.zhao@intel.com> On Mon, May 08, 2023 at 08:58:42PM GMT, Yan Zhao wrote: > In VFIO type1, vaddr_get_pfns() will try fault in MMIO PFNs after > pin_user_pages_remote() returns -EFAULT. > > follow_fault_pfn > fixup_user_fault > handle_mm_fault > handle_mm_fault > do_fault > do_shared_fault > do_fault > __do_fault > vfio_pci_mmap_fault > io_remap_pfn_range > remap_pfn_range > track_pfn_remap > vm_flags_set ==> mmap_assert_write_locked(vma->vm_mm) > remap_pfn_range_notrack > vm_flags_set ==> mmap_assert_write_locked(vma->vm_mm) > > As io_remap_pfn_range() will call vm_flags_set() to update vm_flags [1], > holding of mmap write lock is required. > So, update vfio_pci_mmap_fault() to drop mmap read lock and take mmap > write lock. > > [1] https://lkml.kernel.org/r/20230126193752.297968-3-surenb@google.com > commit bc292ab00f6c ("mm: introduce vma->vm_flags wrapper functions") > commit 1c71222e5f23 > ("mm: replace vma->vm_flags direct modifications with modifier calls") > With linux-next I started noticing traces similar to the above without lockdep, since it has ba168b52bf8e ("mm: use rwsem assertion macros for mmap_lock"). Were there any follow ups to this? Sorry if my quick searching missed it. Thanks, drew