linux-kernel - Re: [RFC PATCH 11/21] vfio/pci: Skip clearing bus master on live update device during kexec

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aPM9Eie71YsJKdak@wunner.de>
Date: Sat, 18 Oct 2025 09:09:06 +0200
From: Lukas Wunner <lukas@...ner.de>
To: Vipin Sharma <vipinsh@...gle.com>
Cc: bhelgaas@...gle.com, alex.williamson@...hat.com,
	pasha.tatashin@...een.com, dmatlack@...gle.com, jgg@...pe.ca,
	graf@...zon.com, pratyush@...nel.org, gregkh@...uxfoundation.org,
	chrisl@...nel.org, rppt@...nel.org, skhawaja@...gle.com,
	parav@...dia.com, saeedm@...dia.com, kevin.tian@...el.com,
	jrhilke@...gle.com, david@...hat.com, jgowans@...zon.com,
	dwmw2@...radead.org, epetron@...zon.de, junaids@...gle.com,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	kvm@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [RFC PATCH 11/21] vfio/pci: Skip clearing bus master on live
 update device during kexec

On Fri, Oct 17, 2025 at 05:07:03PM -0700, Vipin Sharma wrote:
> Set skip_kexec_clear_master on live update prepare() so that the device
> participating in live update can continue to perform DMA during kexec
> phase.

Instead of introducing the skip_kexec_clear_master flag,
could you introduce a function to check whether a device
participates in live update and call that in pci_device_shutdown()?

I think that would be cleaner.  Otherwise someone reading
the code has to chase down the meaning of skip_kexec_clear_master,
i.e. search for places where the bit is set.

When the device is unbound from vfio-pci, don't you have to
clear the skip_kexec_clear_master flag?  I'm not seeing this
in your patches but maybe I'm missing something.  That problem
would solve itself if you follow the suggestion above.

Thanks,

Lukas