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From: "Michael S. Tsirkin" <mst@redhat.com>
To: Jason Wang <jasowang@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>,
	virtualization@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org, xieyongji@bytedance.com,
	stefanha@redhat.com, file@sect.tu-berlin.de,
	ashish.kalra@amd.com, martin.radev@aisec.fraunhofer.de,
	konrad.wilk@oracle.com, kvm@vger.kernel.org
Subject: Re: [RFC PATCH 0/7] Untrusted device support for virtio
Date: Fri, 23 Apr 2021 16:14:32 -0400
Message-ID: <20210423161114-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <0c61dcbb-ac5b-9815-a4a1-5f93ae640011@redhat.com>

On Thu, Apr 22, 2021 at 04:19:16PM +0800, Jason Wang wrote:
> 
> 在 2021/4/22 下午2:31, Christoph Hellwig 写道:
> > On Wed, Apr 21, 2021 at 11:21:10AM +0800, Jason Wang wrote:
> > > The behaivor for non DMA API is kept for minimizing the performance
> > > impact.
> > NAK.  Everyone should be using the DMA API in a modern world.  So
> > treating the DMA API path worse than the broken legacy path does not
> > make any sense whatsoever.
> 
> 
> I think the goal is not treat DMA API path worse than legacy. The issue is
> that the management layer should guarantee that ACCESS_PLATFORM is set so
> DMA API is guaranteed to be used by the driver. So I'm not sure how much
> value we can gain from trying to 'fix' the legacy path. But I can change the
> behavior of legacy path to match DMA API path.
> 
> Thanks

I think before we maintain different paths with/without ACCESS_PLATFORM
it's worth checking whether it's even a net gain. Avoiding sharing
by storing data in private memory can actually turn out to be
a net gain even without DMA API.

It is worth checking what is the performance effect of this patch.


-- 
MST


  reply index

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-21  3:21 Jason Wang
2021-04-21  3:21 ` [RFC PATCH 1/7] virtio-ring: maintain next in extra state for packed virtqueue Jason Wang
2021-04-21  3:21 ` [RFC PATCH 2/7] virtio_ring: rename vring_desc_extra_packed Jason Wang
2021-04-21  3:21 ` [RFC PATCH 3/7] virtio-ring: factor out desc_extra allocation Jason Wang
2021-04-21  3:21 ` [RFC PATCH 4/7] virtio_ring: secure handling of mapping errors Jason Wang
2021-04-21  3:21 ` [RFC PATCH 5/7] virtio_ring: introduce virtqueue_desc_add_split() Jason Wang
2021-04-21  3:21 ` [RFC PATCH 6/7] virtio: use err label in __vring_new_virtqueue() Jason Wang
2021-04-21  3:21 ` [RFC PATCH 7/7] virtio-ring: store DMA metadata in desc_extra for split virtqueue Jason Wang
2021-04-22  6:31 ` [RFC PATCH 0/7] Untrusted device support for virtio Christoph Hellwig
2021-04-22  8:19   ` Jason Wang
2021-04-23 20:14     ` Michael S. Tsirkin [this message]
2021-04-25  1:43       ` Jason Wang
2021-04-28 21:06 ` Konrad Rzeszutek Wilk
2021-04-29  4:16   ` Jason Wang
2021-06-04 15:17     ` Konrad Rzeszutek Wilk
2021-06-07  2:46       ` Jason Wang

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