On 2012-03-16 09:38, Wen Congyang wrote: > At 03/16/2012 04:27 PM, Jan Kiszka Wrote: >> On 2012-03-16 03:38, Wen Congyang wrote: >>> At 03/15/2012 06:21 PM, Wen Congyang Wrote: >>>> Hi all >>>> >>>> When I use pci-assign, I meet the following error: >>>> >>>> Failed to assign irq for "hostdev0": Input/output error >>>> Perhaps you are assigning a device that shares an IRQ with another device? >>>> >>>> Is it a bug or I miss something? >>> >>> Hi, Jan >>> >>> This problem is caused by your patch: >>> commit 6919115a8715c34cd80baa08422d90496f11f5d7 >>> Author: Jan Kiszka <jan.kis...@siemens.com> >>> Date: Thu Mar 8 11:10:27 2012 +0100 >>> >>> pci_assign: Flip defaults of prefer_msi and share_intx >>> >>> INTx sharing is a bit more expensive than exclusive host interrupts, but >>> this channel is not supposed to be used for high-performance scenarios >>> anyway. Modern devices support MSI/MSI-X and do not depend on using INTx >>> under critical workload, real old devices do not support INTx sharing >>> anyway. >>> >>> For those in the middle, the user experience is much better if they just >>> work even when IRQ sharing is required. If there is nothing to share, >>> share_intx=off can still be applied as tuning parameter. >>> >>> With INTx sharing as default, the primary reason for prefer_msi=on is >>> gone. Make it default off, specifically as it is known to cause troubles >>> with devices that have incomplete/broken MSI support or otherwise >>> stumble if host IRQ configuration does not match guest driver >>> expectation. >>> >>> Acked-by: Alex Williamson <alex.william...@redhat.com> >>> Signed-off-by: Jan Kiszka <jan.kis...@siemens.com> >>> Signed-off-by: Marcelo Tosatti <mtosa...@redhat.com> >>> >>> If I revert this commit. qemu can work. >>> >> >> This should be "solvable" by passing prefer_msi=on to the pci-assign >> device, or likely by updating your host kernel to latest kvm.git (to >> enable INTx sharing). > > Is there some way to find out if the kernel supports to enable INTx > sharing?
QEMU does a feature check, but as a user you simply have to know which kernel version includes it (will be 3.4 or 3.5). Of course, that's not really handy. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
