Re: [RESEND PATCH v2 0/6] vfio-pci: Add support for mmapping MSI-X table

[Yongji Xie]

Hi, Eric

On 2016/6/8 15:41, Auger Eric wrote:

> Hi Yongji,
>
> Le 02/06/2016 Ã 08:09, Yongji Xie a Ãcrit :
> > Current vfio-pci implementation disallows to mmap the page
> > containing MSI-X table in case that users can write directly
> > to MSI-X table and generate an incorrect MSIs.
> >
> > However, this will cause some performance issue when there
> > are some critical device registers in the same page as the
> > MSI-X table. We have to handle the mmio access to these
> > registers in QEMU emulation rather than in guest.
> >
> > To solve this issue, this series allows to expose MSI-X table
> > to userspace when hardware enables the capability of interrupt
> > remapping which can ensure that a given PCI device can only
> > shoot the MSIs assigned for it. And we introduce a new bus_flags
> > PCI_BUS_FLAGS_MSI_REMAP to test this capability on PCI side
> > for different archs.
> >
> > The patch 3 are based on the proposed patchset[1].
> You may have noticed I sent a respin of [1] yesterday:
> http://www.gossamer-threads.com/lists/linux/kernel/2455187.
>
> Unfortunately you will see I removed the patch defining the new
> msi_domain_info MSI_FLAG_IRQ_REMAPPING flag you rely on in this series.
> I did so because I was not using it anymore. At the beginning this was
> used to detect whether the MSI assignment was safe but this
> method was covering cases where the MSI controller was
> upstream to the IOMMU. So now I rely on a mechanism where MSI controller
> are supposed to register their MSI doorbells and tag whether it is safe.
>
> I don't know yet how this change will be welcomed though. Depending
> on reviews/discussions, might happen we revert to the previous flag.
>
> If you need the feature you can embed the used patches in your series and
> follow the review process separately. Sorry for the setback.

Thanks for your notification. I'd better wait until your patches get
settled. Then I could exactly know which way we should use to test the
capability of interrupt remapping on ARM in my series.

Thanks,
Yongji