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From: Pavel Fedin
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Date: Thu, 12 Nov 2015 17:35:17 +0300
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Subject: Re: [Qemu-devel] [PATCH] vfio: Fix handling
VFIO_IOMMU_GET_INFO results
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To: 'Alex Williamson'
Cc: qemu-devel@nongnu.org
Hello!
> > Kernel headers define VFIO_IOMMU_INFO_PGSIZES flag, however it has
> > actually been never used, probably by mistake which now became a =
part
> > of the ABI. The kernel always sets info.flags to 0:
>=20
> I don't see how this implies that it becomes part of the ABI. In =
fact,
> as the defacto userspace driver for vfio, QEMU honoring the flag and =
not
> using the value the kernel provides implies the ABI is still valid. =
We
> should fix the kernel instead.
Well... I intentionally put two links to LXR. From the very beginning, =
this ioctl returned valid page sizes. And it never set this flag. We =
simply cannot have a kernel which does not report page sizes.
If we fix qemu, it will automatically start working with all available =
kernels which are there in the wild. If we fix kernel, older versions =
will still not work, however they can.
That's why i think that we should adapt qemu to what already exists. =
But, well, you are The Boss, so you can just say "i don't care". So, =
just let me now if you strongly disagree with this.
Kind regards,
Pavel Fedin
Expert Engineer
Samsung Electronics Research center Russia