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Date:   Wed, 30 Jun 2021 07:49:05 +0100
From:   Christoph Hellwig <hch@infradead.org>
To:     Jason Gunthorpe <jgg@nvidia.com>
Cc:     Alex Williamson <alex.williamson@redhat.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        "Tian, Kevin" <kevin.tian@intel.com>,
        "Jiang, Dave" <dave.jiang@intel.com>,
        "Raj, Ashok" <ashok.raj@intel.com>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        Jonathan Corbet <corbet@lwn.net>,
        David Woodhouse <dwmw2@infradead.org>,
        Jason Wang <jasowang@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Kirti Wankhede <kwankhede@nvidia.com>,
        "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Robin Murphy <robin.murphy@arm.com>,
        David Gibson <david@gibson.dropbear.id.au>
Subject: Re: [RFC] /dev/ioasid uAPI proposal
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On Mon, Jun 07, 2021 at 04:08:02PM -0300, Jason Gunthorpe wrote:
> Compatibility is important, but when I look in the kernel code I see
> very few places that call wbinvd(). Basically all DRM for something
> relavent to qemu.
> 
> That tells me that the vast majority of PCI devices do not generate
> no-snoop traffic.

Part of it is that we have no general API for it, because the DRM folks
as usual just tarted piling up local hacks instead of introducing
a proper API..