RE: [RFC v3 2/3] virtio: Introduce Vdmabuf driver

Hi Christian,

Hi Vivek,

quoted

[Kasireddy, Vivek] What if I do mmap() on the fd followed by mlock()
or mmap() followed by get_user_pages()? If it still fails, would
ioremapping the device memory and poking at the backing storage be an
option? Or, if I bind the passthrough'd GPU device to vfio-pci and tap
into the memory region associated with the device memory, can it be made to work?

get_user_pages() is not allowed on mmaped DMA-bufs in the first place.

Daniel is currently adding code to make sure that this is never ever used.

quoted

And, I noticed that for PFNs that do not have valid struct page
associated with it, KVM does a memremap() to access/map them. Is this an option?

No, even for system memory which has a valid struct page touching it when it is part of a
DMA-buf is illegal since the reference count and mapping fields in struct page might be
used for something different.

Keep in mind that struct page is a heavily overloaded structure for different use cases. You
can't just use it for a different use case than what the owner of the page has intended it.

[Kasireddy, Vivek] What is your recommended/acceptable way for doing what I am trying to 
do?

Thanks,
Vivek

Regards,
Christian.

quoted

Thanks,
Vivek

quoted

take care,
   Gerd

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