Re: [virtio-dev] [RFC] virtio-iommu version 0.4

[Jean-Philippe Brucker <jean-philippe.brucker@arm.com>]

Hi Eric,

On 03/10/17 14:04, Auger Eric wrote:
> When rebasing the v0.4 driver on master I observe a regression: commands
> are not received properly by QEMU (typically an attach command is
> received with a type of 0). After a bisection of the guest kernel the
> first commit the problem appears is:
> 
> commit e3067861ba6650a566a6273738c23c956ad55c02
> arm64: add basic VMAP_STACK support

Indeed, thanks for the report. I can reproduce the problem with 4.14 and
kvmtool. We should allocate buffers on the heap for any request (see for
example 9472fe704 or e37e2ff35). I rebased onto 4.14 and pushed the
following patch at: git://linux-arm.org/linux-jpb.git virtio-iommu/v0.4.1

It's not very nice, but should fix the issue. I didn't manage to measure
the difference though, my benchmark isn't precise enough. So I don't
know if we should try to use a kmem cache instead of kmalloc.

Thanks,
Jean

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