Re: [RFC PATCH 0/5] madvise MADV_DOEXEC

[Steven Sistare]

On 7/31/2020 12:56 PM, Jason Gunthorpe wrote:
> On Fri, Jul 31, 2020 at 12:11:52PM -0400, Steven Sistare wrote:
>>> Your preservation-across-exec use-case might or might not need the
>>> VMA to be mapped at the same address.  
>>
>> It does.  qemu registers memory with vfio which remembers the va's in kernel
>> metadata for the device.
> 
> Once the memory is registered with vfio the VA doesn't matter, vfio
> will keep the iommu pointing at the same physical pages no matter
> where they are mapped.

Yes, but there are other code paths that compute and use offsets between va and the
base va.  Mapping at a different va in the new process breaks vfio; I have tried it.

- Steve