Re: [Qemu-devel] pci-assign can not work
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 >>> 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 >>> Signed-off-by: Jan Kiszka >>> Signed-off-by: Marcelo Tosatti >>> >>> 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
Re: [Qemu-devel] pci-assign can not work
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 >> 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 >> Signed-off-by: Jan Kiszka >> Signed-off-by: Marcelo Tosatti >> >> 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? Thanks Wen Congyang > > Hmm, unfortunate. We needed a conditional default for the prefer_msi > property here. If INTx sharing doesn't work for some reason AND the user > did not ask for disabling the host-side MSI usage, we should fall back > to it again. > > Markus, is there some easy way to find out if a specific qdev property > was set due to a command line switch or was defined by the default value? > > Jan >
Re: [Qemu-devel] pci-assign can not work
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 > 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 > Signed-off-by: Jan Kiszka > Signed-off-by: Marcelo Tosatti > > 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). Hmm, unfortunate. We needed a conditional default for the prefer_msi property here. If INTx sharing doesn't work for some reason AND the user did not ask for disabling the host-side MSI usage, we should fall back to it again. Markus, is there some easy way to find out if a specific qdev property was set due to a command line switch or was defined by the default value? Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux
Re: [Qemu-devel] pci-assign can not work
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 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 Signed-off-by: Jan Kiszka Signed-off-by: Marcelo Tosatti If I revert this commit. qemu can work. Thanks Wen Congyang > > I use libvirt to start the guest, and the user/group is root/root(not > qemu/qemu). > > If I use the default qemu(provided in RHEL6.2), the guest can be started. > > Thanks > Wen Congyang > >
[Qemu-devel] pci-assign can not work
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? I use libvirt to start the guest, and the user/group is root/root(not qemu/qemu). If I use the default qemu(provided in RHEL6.2), the guest can be started. Thanks Wen Congyang
