From mboxrd@z Thu Jan  1 00:00:00 1970
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [RFC PATCH kernel] vfio-pci: Allow write combining
Date: Mon, 16 Oct 2017 10:38:18 +0200
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Cc: Alex Williamson <alex.williamson@redhat.com>, kvm@vger.kernel.org,
        Eric Auger <eric.auger@redhat.com>
To: Alexey Kardashevskiy <aik@ozlabs.ru>,
        David Gibson <david@gibson.dropbear.id.au>
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On Mon, 2017-10-16 at 18:36 +1100, Alexey Kardashevskiy wrote:
> 
> 1. Allow msix mapping to the userspace (to address non-64k-aligned msix bar)
> 
> 2. Allow write combining in vfio for the userspace (kvm guest is kinda
> special and may simply ignore mapping flags in some configs but PPC radix
> guests still rely on this)

Why ? The "G" bit is entirely under control of the guest afaik. This
would only affect qemu itself. It's still useful for things like dpdk
using vfio.

> 3. what callback and where needs to be added to inform HV/PR KVM about VFIO
> group, like IOMMUMR::add_vfio_group() proposal or something.

Can you elaborate a bit ? I haven't followed this.

Cheers,
Ben.