linux-kernel - Re: [PATCH] virtio: Force DMA restricted devices through DMA API

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Message-ID: <YtbTGjRw65QEKkQA@infradead.org>
Date:   Tue, 19 Jul 2022 08:51:54 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Keir Fraser <keirf@...gle.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>, kernel-team@...roid.com,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] virtio: Force DMA restricted devices through DMA API

On Tue, Jul 19, 2022 at 03:46:08PM +0000, Keir Fraser wrote:
> However, if the general idea at least is acceptable, would the
> implementation be acceptable if I add an explicit API for this to the
> DMA subsystem, and hide the detail there?

I don't think so.  The right thing to key off is
VIRTIO_F_ACCESS_PLATFORM, which really should be set in any modern
virtio device after all the problems we had with the lack of it.

> Or a completely different approach would be to revert the patch
> e41b1355508d which clears VIRTIO_F_ACCESS_PLATFORM in the balloon
> driver. MST: That's back in your court, as it's your patch!

Which also means this needs to be addresses, but I don't think a
simple revert is enough.