From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-107.mta0.migadu.com [91.218.175.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5B4663C4B8E for ; Fri, 25 Sep 2026 04:47:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.107 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790311634; cv=none; b=fCbG45eLdJzmv63ydfsXuho8Kpy/Fj6MRRJIYSVpwKaiPVPrEUgUDj4IIHaxI5lU62A2+3MB21lQWphKK5n9i2MwsreEAiHL//vpfLoZ1dK9is1d6nC9xNBCM7yXlr73RpHsBPXn4pb7WQ0suJij0sC5BrGA8jOswkLwuUEzC6k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790311634; c=relaxed/simple; bh=jh8C5ShYQXr3viaQ/Mi2fvp0GqNzxRBy1mECrQ4hGaU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=i/deltwXektpEdYmN1BWj26yOHPcicX4i+GjOpJ25l9fMbldybnYaXBTUe/KWcC052S9HbVTlW48vbqVoIdPNR3I6S9QQ53SldwM7Bk6ptFf8ktMLy/4EvZlhWrmsmmeB1QfaWquwE7yNP1ffgHKj2LpF7WA3+CaLAiB0fuMDVg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=FCNIHfma; arc=none smtp.client-ip=91.218.175.107 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="FCNIHfma" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=jh8C5ShYQXr3viaQ/Mi2fvp0GqNzxRBy1mECrQ4hGaU=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1790311630; v=1; x=1790916430; b=FCNIHfma3LS/3JaA2BJJYgDvh1b5rgyweLTodShdjDg10c9sNGQLzo2UvkvnwLTdJtjoIrS7 mMXE2rZi3p1dVlTJpgMILbaFwI/JbzCqyKkox75GhQxTTxTX2sEMVAnja/huZQTORQDsTLPa2mX vlIlxjfm+N/2uTk4OrJ46b9c= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id f70f5b72ae709b91; 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 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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