On Tue, May 12, 2026 at 06:48:45PM +0000, David Matlack wrote: > Do not disable bus mastering on outgoing preserved devices during > pci_device_shutdown() for kexec. > > Preserved devices must be allowed to perform memory transactions during > a Live Update to minimize downtime and ensure continuous operation. > Clearing the bus mastering bit would prevent these devices from issuing > any memory requests while the new kernel boots.
s/minimize downtime and// Ensuring continuous operation is the critical piece here. Minimizing downtime is always good but IMO it's not actually a reason for this change. I guess what this is probably saying is that the continuous operation and Live Update are what minimizes downtime, and preserving bus mastering is a piece of that. > Because bridges upstream of preserved endpoint devices are also > automatically preserved, this change also avoids clearing bus mastering > on them. This is critical because clearing bus mastering on an upstream > bridge prevents the bridge from forwarding memory requests upstream (i.e. > it would prevent the endpoint device from accessing system RAM and doing > peer-to-peer transactions with devices not downstream of the bridge).
