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

[Yi Min Zhao <zyimin@linux.vnet.ibm.com>]

在 2017/8/28 下午10:51, Cornelia Huck 写道:
> On Mon, 28 Aug 2017 10:04:44 +0200
> Yi Min Zhao <zyimin@linux.vnet.ibm.com> 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 <bjsdjshi@linux.vnet.ibm.com>
>> Reviewed-by: Pierre Morel <pmorel@linux.vnet.ibm.com>
>> Signed-off-by: Yi Min Zhao <zyimin@linux.vnet.ibm.com>
>> ---
>>   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.