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Fri, 25 Sep 2026 04:47:10 +0000 X-Mizu-Trace-ID: f70f5b72ae709b91 X-Migadu-Flow: FLOW_OUT Message-ID: Date: Thu, 24 Sep 2026 21:47:03 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 00/13] PCI: liveupdate: PCI core support for Live Update To: David Matlack Cc: kexec@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, Adithya Jayachandran , Alexander Graf , Alex Williamson , Bjorn Helgaas , Chris Li , David Rientjes , Jacob Pan , Jason Gunthorpe , Jonathan Corbet , Josh Hilke , Leon Romanovsky , Lukas Wunner , Mike Rapoport , Parav Pandit , Pasha Tatashin , Pranjal Shrivastava , Pratyush Yadav , Randy Dunlap , Saeed Mahameed , Samiullah Khawaja , Shuah Khan , Vipin Sharma , William Tu , Yi Liu , "yanjun.zhu@linux.dev" References: <20260918200640.887030-1-dmatlack@google.com> <2e88b92a-d3f2-41f7-bdbe-11fd71690606@linux.dev> From: Zhu Yanjun In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: AAD1680002 X-Stat-Signature: wfkd73he93wodxinesqfmuijbkm57e9s X-Rspam-User: X-HE-Tag: 1790311631-16875 X-HE-Meta: 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 T9N1x1lE 9OiSfzFSGzV0X0IaX9tJkwxvDOH4O392nVTy5lzb1Ux1IWQUbYvpqWaP1TntU+mHfwhjeSwmJjzXokZN+6wpElxOAFAli50CQInwPTXjoWWNWO4HuN6BUq8SpAtBnC2nS0zRJSH2AsfwerOUQO2B+G5XDCZujwzF4vY+IB0vinbvpRuJVdEUfeStlT9CKjhKJByjIj95u0xGvu/6JYev7f/3jr2eX5jt9nJOJqFkcs587dS6vpeUJNtIkrOgRproeJkqQqzzzvpiZW8VsyJQjgRWaYgrxZ/2IY1BwWDl4Mb8kgslNV47fgp50JSvr+qfMQt8JGUg0pn5GcXS2wmz3Pq1BDnSr7dG4zr/pcbRECYI00hf3grFUjno01D9sq/xK309oK39jE37Cpg4= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 在 2026/9/22 11:53, David Matlack 写道: > On Tue, Sep 22, 2026 at 11:36 AM Zhu Yanjun wrote: >> 在 2026/9/18 13:06, David Matlack 写道: >>> Future Work >>> ----------- >>> >>> Following this series, we expect to make further improvements to the PCI >>> core support for Live Update: >>> >>> - Allow P2P across Live Update by avoiding resizing or moving >>> preserved device BARs and preserving all upstream bridge windows. >>> >>> - Support preserving Virtual Functions by preserving SR-IOV >>> configuration on PFs and enumerating VFs after Live Update. >> Preserving the PCIe topology, bus numbers, ACS, and Bus Mastering across >> kexec is a foundational step for minimizing downtime. >> >> As we look toward complete end-to-end support for DMA preservation >> across Live Update—especially for VFIO device passthrough and dma-buf >> sharing scenarios—IOMMU table/domain preservation becomes crucial to >> prevent IOMMU page faults when devices continue performing DMA during kexec. >> >> I would like to ask about the current status and roadmap regarding IOMMU >> Live Update / KHO (Kexec Handover) support: >> >> Is there an ongoing effort or RFC series for IOMMU handover / page-table >> preservation currently in development or under discussion? >> >> How is the coordination between the PCI core Live Update mechanisms and >> the IOMMU subsystem being envisioned for preserving IOVA mappings (e.g., >> restoring domains or handing over root tables)? >> >> Any pointers to active discussion threads, RFCs, or future plans >> regarding IOMMU participation in Live Update would be greatly appreciated. > The first IOMMU series to support Live update, can be found here: > > https://lore.kernel.org/linux-iommu/20260921004834.2601285-1-skhawaja@google.com/ After cloning the source code from samikhawaja/linux, branch iommu/phase1-v5, I tested the VFIO live update functionality in my local KVM environment and encountered the following issue. When I run the following commands to verify that VFIO live update works correctly, I get the output shown below. I am currently testing with VFIO v5 and PCI core v9, and I am not sure whether this behavior is expected. Interestingly, when I revert the following commit: vfio/pci: Preserve the iommufd state of the vfio cdev the issue disappears. Could you please let me know whether this is expected behavior, or whether it indicates a problem with the current VFIO live update implementation? " echo "vfio-pci" > /sys/bus/pci/devices/0000:00:04.0/driver_override echo "0000:00:04.0" > /sys/bus/pci/drivers/vfio-pci/bind Preserving device in session vfio_pci_liveupdate_kexec_test.c:122: Assertion Failure   Expression: ret == 0   Observed: 0xffffffffffffffea == 0   [errno: 22 - Invalid argument] " Thanks a lot. Yanjun Zhu > > The IOMMU series builds on top of the PCI core support (this series) > and the VFIO series linked further up in the cover letter. -- Best Regards, Yanjun.Zhu