Am 03.11.2010 10:05, Michael S. Tsirkin wrote: > On Wed, Nov 03, 2010 at 09:51:10AM +0100, Jan Kiszka wrote: >> Am 03.11.2010 09:43, Michael S. Tsirkin wrote: >>> On Wed, Nov 03, 2010 at 09:11:16AM +0100, Jan Kiszka wrote: >>>> From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> >>>> >>>> PCI 2.3 allows to generically disable IRQ sources at device level. This >>>> enables us to share IRQs of such devices between on the host side when >>>> passing them to a guest. This feature is optional, user space has to >>>> request it explicitly. >>>> >>>> Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> >>> >>> >>> I just realized something. >>> With this patch, if guest ever looks at >>> interrupt disable bit, it will go crazy as that bit goes on/off by >>> itself. I guess we could have an ioctl to set/clear the bit on >>> device, and have qemu call that on config write into command/status >>> register. >> >> I understand the problem, but I don't get why the kernel should bother. >> User space has to filter the config space access, returning precisely >> the value of the INTx disabled bit that the guest wrote. > > Yes but if guest disables INTx it should not get interrupts :) Right, got this meanwhile. KVM-in-KVM with nested device assignment would break otherwise - intolerable. :) Jan
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