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([2a01:e0a:280:24f0:576b:abc6:6396:ed4a]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46d7a566a27sm63754735e9.20.2025.09.23.00.06.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 23 Sep 2025 00:06:59 -0700 (PDT) Message-ID: Date: Tue, 23 Sep 2025 09:06:57 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/5] vfio/iommufd: Add framework code to support getting dirty bitmap before unmap To: "Duan, Zhenzhong" , "qemu-devel@nongnu.org" Cc: "alex.williamson@redhat.com" , "mst@redhat.com" , "jasowang@redhat.com" , "Liu, Yi L" , "clement.mathieu--drif@eviden.com" , "eric.auger@redhat.com" , "joao.m.martins@oracle.com" , "avihaih@nvidia.com" , "Hao, Xudong" , "Cabiddu, Giovanni" , "Gross, Mark" , "Van De Ven, Arjan" References: <20250910023701.244356-1-zhenzhong.duan@intel.com> <20250910023701.244356-2-zhenzhong.duan@intel.com> From: =?UTF-8?Q?C=C3=A9dric_Le_Goater?= Content-Language: en-US, fr Autocrypt: addr=clg@redhat.com; keydata= xsFNBFu8o3UBEADP+oJVJaWm5vzZa/iLgpBAuzxSmNYhURZH+guITvSySk30YWfLYGBWQgeo 8NzNXBY3cH7JX3/a0jzmhDc0U61qFxVgrPqs1PQOjp7yRSFuDAnjtRqNvWkvlnRWLFq4+U5t yzYe4SFMjFb6Oc0xkQmaK2flmiJNnnxPttYwKBPd98WfXMmjwAv7QfwW+OL3VlTPADgzkcqj 53bfZ4VblAQrq6Ctbtu7JuUGAxSIL3XqeQlAwwLTfFGrmpY7MroE7n9Rl+hy/kuIrb/TO8n0 ZxYXvvhT7OmRKvbYuc5Jze6o7op/bJHlufY+AquYQ4dPxjPPVUT/DLiUYJ3oVBWFYNbzfOrV RxEwNuRbycttMiZWxgflsQoHF06q/2l4ttS3zsV4TDZudMq0TbCH/uJFPFsbHUN91qwwaN/+ gy1j7o6aWMz+Ib3O9dK2M/j/O/Ube95mdCqN4N/uSnDlca3YDEWrV9jO1mUS/ndOkjxa34ia 70FjwiSQAsyIwqbRO3CGmiOJqDa9qNvd2TJgAaS2WCw/TlBALjVQ7AyoPEoBPj31K74Wc4GS Rm+FSch32ei61yFu6ACdZ12i5Edt+To+hkElzjt6db/UgRUeKfzlMB7PodK7o8NBD8outJGS tsL2GRX24QvvBuusJdMiLGpNz3uqyqwzC5w0Fd34E6G94806fwARAQABzSJDw6lkcmljIExl IEdvYXRlciA8Y2xnQHJlZGhhdC5jb20+wsGRBBMBCAA7FiEEoPZlSPBIlev+awtgUaNDx8/7 7KEFAmTLlVECGwMFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AACgkQUaNDx8/77KG0eg// S0zIzTcxkrwJ/9XgdcvVTnXLVF9V4/tZPfB7sCp8rpDCEseU6O0TkOVFoGWM39sEMiQBSvyY lHrP7p7E/JYQNNLh441MfaX8RJ5Ul3btluLapm8oHp/vbHKV2IhLcpNCfAqaQKdfk8yazYhh EdxTBlzxPcu+78uE5fF4wusmtutK0JG0sAgq0mHFZX7qKG6LIbdLdaQalZ8CCFMKUhLptW71 xe+aNrn7hScBoOj2kTDRgf9CE7svmjGToJzUxgeh9mIkxAxTu7XU+8lmL28j2L5uNuDOq9vl hM30OT+pfHmyPLtLK8+GXfFDxjea5hZLF+2yolE/ATQFt9AmOmXC+YayrcO2ZvdnKExZS1o8 VUKpZgRnkwMUUReaF/mTauRQGLuS4lDcI4DrARPyLGNbvYlpmJWnGRWCDguQ/LBPpbG7djoy k3NlvoeA757c4DgCzggViqLm0Bae320qEc6z9o0X0ePqSU2f7vcuWN49Uhox5kM5L86DzjEQ RHXndoJkeL8LmHx8DM+kx4aZt0zVfCHwmKTkSTQoAQakLpLte7tWXIio9ZKhUGPv/eHxXEoS 0rOOAZ6np1U/xNR82QbF9qr9TrTVI3GtVe7Vxmff+qoSAxJiZQCo5kt0YlWwti2fFI4xvkOi V7lyhOA3+/3oRKpZYQ86Frlo61HU3r6d9wzOwU0EW7yjdQEQALyDNNMw/08/fsyWEWjfqVhW pOOrX2h+z4q0lOHkjxi/FRIRLfXeZjFfNQNLSoL8j1y2rQOs1j1g+NV3K5hrZYYcMs0xhmrZ KXAHjjDx7FW3sG3jcGjFW5Xk4olTrZwFsZVUcP8XZlArLmkAX3UyrrXEWPSBJCXxDIW1hzwp bV/nVbo/K9XBptT/wPd+RPiOTIIRptjypGY+S23HYBDND3mtfTz/uY0Jytaio9GETj+fFis6 TxFjjbZNUxKpwftu/4RimZ7qL+uM1rG1lLWc9SPtFxRQ8uLvLOUFB1AqHixBcx7LIXSKZEFU CSLB2AE4wXQkJbApye48qnZ09zc929df5gU6hjgqV9Gk1rIfHxvTsYltA1jWalySEScmr0iS YBZjw8Nbd7SxeomAxzBv2l1Fk8fPzR7M616dtb3Z3HLjyvwAwxtfGD7VnvINPbzyibbe9c6g LxYCr23c2Ry0UfFXh6UKD83d5ybqnXrEJ5n/t1+TLGCYGzF2erVYGkQrReJe8Mld3iGVldB7 JhuAU1+d88NS3aBpNF6TbGXqlXGF6Yua6n1cOY2Yb4lO/mDKgjXd3aviqlwVlodC8AwI0Sdu jWryzL5/AGEU2sIDQCHuv1QgzmKwhE58d475KdVX/3Vt5I9kTXpvEpfW18TjlFkdHGESM/Jx IqVsqvhAJkalABEBAAHCwV8EGAECAAkFAlu8o3UCGwwACgkQUaNDx8/77KEhwg//WqVopd5k 8hQb9VVdk6RQOCTfo6wHhEqgjbXQGlaxKHoXywEQBi8eULbeMQf5l4+tHJWBxswQ93IHBQjK yKyNr4FXseUI5O20XVNYDJZUrhA4yn0e/Af0IX25d94HXQ5sMTWr1qlSK6Zu79lbH3R57w9j hQm9emQEp785ui3A5U2Lqp6nWYWXz0eUZ0Tad2zC71Gg9VazU9MXyWn749s0nXbVLcLS0yop s302Gf3ZmtgfXTX/W+M25hiVRRKCH88yr6it+OMJBUndQVAA/fE9hYom6t/zqA248j0QAV/p LHH3hSirE1mv+7jpQnhMvatrwUpeXrOiEw1nHzWCqOJUZ4SY+HmGFW0YirWV2mYKoaGO2YBU wYF7O9TI3GEEgRMBIRT98fHa0NPwtlTktVISl73LpgVscdW8yg9Gc82oe8FzU1uHjU8b10lU XOMHpqDDEV9//r4ZhkKZ9C4O+YZcTFu+mvAY3GlqivBNkmYsHYSlFsbxc37E1HpTEaSWsGfA HQoPn9qrDJgsgcbBVc1gkUT6hnxShKPp4PlsZVMNjvPAnr5TEBgHkk54HQRhhwcYv1T2QumQ izDiU6iOrUzBThaMhZO3i927SG2DwWDVzZltKrCMD1aMPvb3NU8FOYRhNmIFR3fcalYr+9gD uVKe8BVz4atMOoktmt0GWTOC8P4= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=clg@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.442, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_PASS=-0.001, T_SPF_HELO_TEMPERROR=0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 9/23/25 04:45, Duan, Zhenzhong wrote: > > >> -----Original Message----- >> From: Cédric Le Goater >> Subject: Re: [PATCH 1/5] vfio/iommufd: Add framework code to support >> getting dirty bitmap before unmap >> >> On 9/22/25 05:17, Duan, Zhenzhong wrote: >>> Hi Cedric, >>> >>>> -----Original Message----- >>>> From: Cédric Le Goater >>>> Subject: Re: [PATCH 1/5] vfio/iommufd: Add framework code to support >>>> getting dirty bitmap before unmap >>>> >>>> Hello Zhenzhong >>>> >>>> On 9/10/25 04:36, Zhenzhong Duan wrote: >>>>> Currently we support device and iommu dirty tracking, device dirty >>>>> tracking is preferred. >>>>> >>>>> Add the framework code in iommufd_cdev_unmap_one() to choose >> either >>>>> device or iommu dirty tracking, just like vfio_legacy_dma_unmap_one(). >>>> >>>> I wonder if commit 567d7d3e6be5 ("vfio/common: Work around kernel >>>> overflow bug in DMA unmap") could be removed now to make the code >>>> common to both VFIO IOMMU Type1 and IOMMUFD backends. >>> >>> I am not clear if there is other reason to keep the workaround, but the >> original >>> kernel issue had been fixed with below commit: >>> >>> commit 58fec830fc19208354895d9832785505046d6c01 >>> Author: Alex Williamson >>> Date: Mon Jan 7 22:13:22 2019 -0700 >>> >>> vfio/type1: Fix unmap overflow off-by-one >>> >>> The below referenced commit adds a test for integer overflow, but in >>> doing so prevents the unmap ioctl from ever including the last page >> of >>> the address space. Subtract one to compare to the last address of >> the >>> unmap to avoid the overflow and wrap-around. >>> >>> Fixes: 71a7d3d78e3c ("vfio/type1: silence integer overflow warning") >>> Link: https://bugzilla.redhat.com/show_bug.cgi?id=1662291 >>> Cc: stable@vger.kernel.org # v4.15+ >>> Reported-by: Pei Zhang >>> Debugged-by: Peter Xu >>> Reviewed-by: Dan Carpenter >>> Reviewed-by: Peter Xu >>> Tested-by: Peter Xu >>> Reviewed-by: Cornelia Huck >>> Signed-off-by: Alex Williamson >>> >>>> >>>> I asked Alex and Peter in another thread. >>> >>> Just curious on the answer, may I ask which thread? >> >> According to Alex, the QEMU workaround can be removed : >> >> https://lore.kernel.org/qemu-devel/20250919102447.748e17fe.alex.williams >> on@redhat.com/ >> >>> btw: I just found unmapping in halves seems unnecessary as both backends >> of kernel side support unmap_all now. >>> >>> if (unmap_all) { >>> /* The unmap ioctl doesn't accept a full 64-bit span. */ >>> Int128 llsize = int128_rshift(int128_2_64(), 1); >>> >>> ret = vfio_legacy_dma_unmap_one(bcontainer, 0, >> int128_get64(llsize), >>> iotlb); >>> >>> if (ret == 0) { >>> ret = vfio_legacy_dma_unmap_one(bcontainer, >> int128_get64(llsize), >>> int128_get64(llsize), >> iotlb); >>> } >>> >>> } else { >>> ret = vfio_legacy_dma_unmap_one(bcontainer, iova, size, >> iotlb); >>> } >> >> Good. So we can simply both backends it seems. *ify > > Will you handle them or not? I mean the workaround removing and unmapping_all optimization. I can revert 567d7d3e6be5 ("vfio/common: Work around kernel overflow bug in DMA unmap") but, AFAICT, the "unmap DMAs in halves" method (see 1b296c3def4b) should be kept. Thanks, C.