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: Wed, 11 Oct 2017 17:35:07 +0200
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Cc: kvm@vger.kernel.org, David Gibson <david@gibson.dropbear.id.au>,
        Eric Auger <eric.auger@redhat.com>
To: Alexey Kardashevskiy <aik@ozlabs.ru>,
        Alex Williamson <alex.williamson@redhat.com>
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On Wed, 2017-10-11 at 13:56 +1100, Alexey Kardashevskiy wrote:
> Oopsie. This is because I overlooked it. Others do not use it. So I do need
> a file. But in the current scheme where all BARs share one fd - it won't
> work - I simply cannot allow WC on non-prefetchable BARs :-/

This is an oversight in the design of VFIO-PCI, it should have a way to
specify write combine, either implicitely via such an arch hook, or
explicitely via an ioctl prior to mapping the BARs for example.

Alex, what do you reckon is the best approach here ?

Cheers,
Ben.