Re: [PATCH] VFIO driver: Non-privileged user level PCI drivers

[Avi Kivity <avi@redhat.com>]

On 05/29/2010 02:55 PM, Arnd Bergmann wrote:
> On Saturday 29 May 2010, Tom Lyon wrote:
>    
>> +/*
>> + * Structure for DMA mapping of user buffers
>> + * vaddr, dmaaddr, and size must all be page aligned
>> + * buffer may only be larger than 1 page if (a) there is
>> + * an iommu in the system, or (b) buffer is part of a huge page
>> + */
>> +struct vfio_dma_map {
>> +       __u64   vaddr;          /* process virtual addr */
>> +       __u64   dmaaddr;        /* desired and/or returned dma address */
>> +       __u64   size;           /* size in bytes */
>> +       int     rdwr;           /* bool: 0 for r/o; 1 for r/w */
>> +};
>>      
> Please add a 32 bit padding word at the end of this, otherwise the
> size of the data structure is incompatible between 32 x86 applications
> and 64 bit kernels.
>    

Might as well call it 'flags' and reserve a bit more space (keeping 
64-bit aligned size) for future expansion.

rdwr can be folded into it.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.