Re: [PATCH v10 10/10] vfio: Don't issue full 2^64 unmap

[Paolo Bonzini]

On 30/10/20 18:26, Alex Williamson wrote:
>>  
>>      if (try_unmap) {
>> +        if (llsize == int128_2_64()) {
>> +            /* The unmap ioctl doesn't accept a full 64-bit span. */
>> +            llsize = int128_rshift(llsize, 1);
>> +            ret = vfio_dma_unmap(container, iova, int128_get64(llsize));
>> +            if (ret) {
>> +                error_report("vfio_dma_unmap(%p, 0x%"HWADDR_PRIx", "
>> +                             "0x%"HWADDR_PRIx") = %d (%m)",
>> +                             container, iova, int128_get64(llsize), ret);
>> +            }
>> +            iova += int128_get64(llsize);
>> +        }
>>          ret = vfio_dma_unmap(container, iova, int128_get64(llsize));
>>          if (ret) {
>>              error_report("vfio_dma_unmap(%p, 0x%"HWADDR_PRIx", "  
> We're still susceptible that splitting the range in two could result in
> unmap calls that attempt to bisect a mapping that spans both ranges.
> Both unmap calls would fail in that case.  I think we could solve this
> more completely with a high water marker, but this probably good enough
> for now.
> 
> Acked-by: Alex Williamson <alex.williamson@redhat.com>  

Could it also be fixed by passing an Int128 to vfio_dma_unmap?

Paolo