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Re: [Qemu-devel] [PATCH] i386: pci-assign: Fix MSI-X table size
From: |
Ido Yariv |
Subject: |
Re: [Qemu-devel] [PATCH] i386: pci-assign: Fix MSI-X table size |
Date: |
Mon, 20 Jun 2016 11:40:17 -0400 |
User-agent: |
Mutt/1.6.1 (2016-04-27) |
Hi Paolo,
On Mon, Jun 20, 2016 at 04:54:17PM +0200, Paolo Bonzini wrote:
> On 18/06/2016 22:42, Ido Yariv wrote:
> > The current code creates a whole page mmio region for the MSI-X table
> > size.
> >
> > However, the page containing the MSI-X table may contain other registers
> > not related to MSI-X. Creating an mmio region for the whole page masks
> > such registers and may break drivers in the guest OS.
> >
> > Since maximal number of entries is known, use that instead to deduce the
> > table size when setting up the mmio region.
> >
> > Signed-off-by: Ido Yariv <address@hidden>
>
> I can take this patch, but I'd like to warn you that pci-assign is
> deprecated (and replaced by VFIO). I seem to recall VFIO does this
> correctly, but it would be great if you could check that.
Just gave it a quick shot and everything seems to be working fine with
VFIO, thanks!
> Also, I would prefer the mmap/munmap to keep using MSIX_PAGE_SIZE, just
> to limit the number of things that could break.
I believe there might be another issue with this. The number of entries
can be up to 2048, so the MSI-X table size can theoretically exceed one
page and take up to 8 pages.
We can just modify MSIX_PAGE_SIZE to 0x8000, but wouldn't it be better
to just map exactly what we need?
Cheers,
Ido.