Messages in this thread | | | Date | Thu, 25 Aug 2011 22:07:49 +0300 | From | "Michael S. Tsirkin" <> | Subject | Re: Broken pci_block_user_cfg_access interface |
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On Thu, Aug 25, 2011 at 08:52:08PM +0200, Jan Kiszka wrote: > On 2011-08-25 20:19, Michael S. Tsirkin wrote: > > On Thu, Aug 25, 2011 at 03:06:01PM +0200, Jan Kiszka wrote: > >>> I took a look at the sysfs triggered pci reset function and don't see any way > >>> that the controlling device driver ever gets to be involved in this reset. > >>> If code outside the ipr driver were to reset the adapter, the adapter firmware > >>> would be left in an uninitialized state and until scsi core starts timing > >>> out ops and driving EH, the card would be unusable. I can't imagine the > >>> ipr driver is unique in this. > >> > >> Right, that's why a PCI core service is needed for coordination. > >> > >> Jan > > > > But why do we want to trigger reset through sysfs while the > > driver runs? > > A perfectly valid race conditions are created by KVM and VFIO: shared > IRQ handler is triggered while the user space part wants to reset the > assigned device.
OK, that would be solved by blocking sysfs reset while config access is blocked, right?
> I'm quite sure that this how I first caused this bug to > show up (it triggered for an assigned device with a shared busy IRQ line > during QEMU startup, ie. the initial guest reset). > > Jan >
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