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SubjectRe: [RFC PATCH 0/3] VFIO: capability chains
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On 11/24/2015 07:43 AM, Alex Williamson wrote:
> Please see the commit log and comments in patch 1 for a general
> explanation of the problems that this series tries to address. The
> general problem is that we have several cases where we want to expose
> variable sized information to the user, whether it's sparse mmaps for
> a region, as implemented here, or DMA mapping ranges of an IOMMU, or
> reserved MSI mapping ranges, etc. Extending data structures is hard;
> extending them to report variable sized data is really hard. After
> considering several options, I think the best approach is to copy how
> PCI does capabilities. This allows the ioctl to only expose the
> capabilities that are relevant for them, avoids data structures that
> are too complicated to parse, and avoids creating a new ioctl each
> time we think of something else that we'd like to report. This method
> also doesn't preclude extensions to the fixed structure since the
> offset of these capabilities is entirely dynamic.
>
> Comments welcome, I'll also follow-up to the QEMU and KVM lists with
> an RFC making use of this for mmaps skipping over the MSI-X table.
> Thanks,

Out of curiosity - could this information be exposed to the userspace via
/sys/bus/pci/devices/xxxx:xx:xx:x/vfio_xxxx? It seems not to change after
vfio_pci driver is bound to a device.




> Alex
>
> ---
>
> Alex Williamson (3):
> vfio: Define capability chains
> vfio: Define sparse mmap capability for regions
> vfio/pci: Include sparse mmap capability for MSI-X table regions
>
>
> drivers/vfio/pci/vfio_pci.c | 101 +++++++++++++++++++++++++++++++++++++++++++
> include/uapi/linux/vfio.h | 53 ++++++++++++++++++++++-
> 2 files changed, 152 insertions(+), 2 deletions(-)
> --
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--
Alexey


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