Re: [Qemu-devel] [PATCH 1/4] s390x/pci: fixup trap_msix()

[Cornelia Huck]

On Tue, 29 Aug 2017 12:32:17 +0800
Yi Min Zhao <address@hidden> wrote:

> 在 2017/8/28 下午10:51, Cornelia Huck 写道:
> > On Mon, 28 Aug 2017 10:04:44 +0200
> > Yi Min Zhao <address@hidden> wrote:
> >  
> >> The function trap_msix() is to check if pcistg instruction would access
> >> msix table entries. The correct boundary condition should be
> >> [table_offset, table_offset+entries*entry_size). But the current
> >> condition calculated misses the last entry. So let's fixup it.
> >>
> >> Acked-by: Dong Jia Shi <address@hidden>
> >> Reviewed-by: Pierre Morel <address@hidden>
> >> Signed-off-by: Yi Min Zhao <address@hidden>
> >> ---
> >>   hw/s390x/s390-pci-inst.c | 4 ++--
> >>   1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/hw/s390x/s390-pci-inst.c b/hw/s390x/s390-pci-inst.c
> >> index b7beb8c36a..eba9ffb5f2 100644
> >> --- a/hw/s390x/s390-pci-inst.c
> >> +++ b/hw/s390x/s390-pci-inst.c
> >> @@ -440,8 +440,8 @@ static int trap_msix(S390PCIBusDevice *pbdev, uint64_t 
> >> offset, uint8_t pcias)
> >>   {
> >>       if (pbdev->msix.available && pbdev->msix.table_bar == pcias &&
> >>           offset >= pbdev->msix.table_offset &&
> >> -        offset <= pbdev->msix.table_offset +
> >> -                  (pbdev->msix.entries - 1) * PCI_MSIX_ENTRY_SIZE) {
> >> +        offset < (pbdev->msix.table_offset +
> >> +                  pbdev->msix.entries * PCI_MSIX_ENTRY_SIZE)) {
> >>           return 1;
> >>       } else {
> >>           return 0;  
> > What happened before due to the miscalculation? Write to wrong memory
> > region?
> >
> >  
> We tried to plug virtio-net pci device but failed. After inspected, we
> found that the device uses two msix entries but the last one was
> missed. Then we cannot register interrupt successfully because we
> should call trap_msixi() in order to save some useful and arch
> information into msix message. But what about wrong memory region
> didn't happen.

So, the guest just was not able to use the second msix entry, but did
not get any exception?