From: Christoph Hellwig <hch@lst.de>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: linux-s390@vger.kernel.org, Janosch Frank <frankja@linux.ibm.com>,
"Lendacky, Thomas" <Thomas.Lendacky@amd.com>,
Jason Wang <jasowang@redhat.com>,
Cornelia Huck <cohuck@redhat.com>, Ram Pai <linuxram@us.ibm.com>,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
Halil Pasic <pasic@linux.ibm.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
iommu@lists.linux-foundation.org,
David Gibson <david@gibson.dropbear.id.au>,
Michael Mueller <mimu@linux.ibm.com>,
Viktor Mihajlovski <mihajlov@linux.ibm.com>,
Robin Murphy <robin.murphy@arm.com>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 2/2] virtio: let virtio use DMA API when guest RAM is protected
Date: Mon, 24 Feb 2020 18:16:57 +0100 [thread overview]
Message-ID: <20200224171657.GB7278@lst.de> (raw)
In-Reply-To: <20200222140408-mutt-send-email-mst@kernel.org>
On Sat, Feb 22, 2020 at 02:07:58PM -0500, Michael S. Tsirkin wrote:
> On Fri, Feb 21, 2020 at 03:33:40PM +0100, Halil Pasic wrote:
> > AFAIU you have a positive attitude towards the idea, that
> > !F_VIRTIO_PLATFORM implies 'no DMA API is used by virtio'
> > should be scrapped.
> >
> > I would like to accomplish that without adverse effects to virtio-ccw
> > (because caring for virtio-ccw is a part of job description).
> >
> > Regards,
> > Halil
>
> It is possible, in theory. IIRC the main challenge is that DMA API
> has overhead of indirect function calls even when all it
> does it return back the PA without changes.
That overhead is gone now, the DMA direct calls are direct calls these
days.
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next prev parent reply other threads:[~2020-02-24 17:17 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-20 16:06 [PATCH 0/2] virtio: decouple protected guest RAM form VIRTIO_F_IOMMU_PLATFORM Halil Pasic
2020-02-20 16:06 ` [PATCH 1/2] mm: move force_dma_unencrypted() to mem_encrypt.h Halil Pasic
2020-02-20 16:11 ` Christoph Hellwig
2020-02-20 16:23 ` Christian Borntraeger
2020-02-20 16:31 ` Christoph Hellwig
2020-02-20 17:00 ` Christian Borntraeger
2020-02-21 3:27 ` David Gibson
2020-02-21 13:06 ` Halil Pasic
2020-02-21 15:48 ` Michael S. Tsirkin
2020-02-21 18:07 ` Halil Pasic
2020-02-24 3:33 ` David Gibson
2020-02-24 18:49 ` Halil Pasic
2020-02-25 18:08 ` Cornelia Huck
2020-02-28 0:23 ` David Gibson
2020-02-20 16:06 ` [PATCH 2/2] virtio: let virtio use DMA API when guest RAM is protected Halil Pasic
2020-02-20 16:13 ` Christoph Hellwig
2020-02-21 2:59 ` David Gibson
2020-02-21 3:41 ` Jason Wang
2020-02-21 13:31 ` Halil Pasic
2020-02-21 13:27 ` Halil Pasic
2020-02-21 16:36 ` Christoph Hellwig
2020-02-24 6:50 ` David Gibson
2020-02-24 18:59 ` Halil Pasic
2020-02-21 14:33 ` Halil Pasic
2020-02-21 16:39 ` Christoph Hellwig
2020-02-21 18:16 ` Halil Pasic
2020-02-22 19:07 ` Michael S. Tsirkin
2020-02-24 17:16 ` Christoph Hellwig [this message]
2020-10-28 14:24 ` Alexander Graf via iommu
2020-10-28 18:01 ` Michael S. Tsirkin
2020-02-20 20:55 ` Michael S. Tsirkin
2020-02-21 1:17 ` Ram Pai
2020-02-21 3:29 ` David Gibson
2020-02-21 13:12 ` Halil Pasic
2020-02-21 15:39 ` Tom Lendacky
2020-02-24 6:40 ` David Gibson
2020-02-21 15:56 ` Michael S. Tsirkin
2020-02-21 16:35 ` Christoph Hellwig
2020-02-21 18:03 ` Halil Pasic
2020-02-20 20:48 ` [PATCH 0/2] virtio: decouple protected guest RAM form VIRTIO_F_IOMMU_PLATFORM Michael S. Tsirkin
2020-02-20 21:29 ` Michael S. Tsirkin
2020-02-21 13:37 ` Halil Pasic
2020-02-20 21:33 ` Michael S. Tsirkin
2020-02-21 13:49 ` Halil Pasic
2020-02-21 16:41 ` Christoph Hellwig
2020-02-24 5:44 ` David Gibson
2020-02-21 6:22 ` Jason Wang
2020-02-21 14:56 ` Halil Pasic
2020-02-24 3:38 ` David Gibson
2020-02-24 4:01 ` Jason Wang
2020-02-24 6:06 ` Michael S. Tsirkin
2020-02-24 6:45 ` Jason Wang
2020-02-24 7:48 ` Michael S. Tsirkin
2020-02-24 9:26 ` Jason Wang
2020-02-24 13:40 ` Michael S. Tsirkin
2020-02-25 3:38 ` Jason Wang
2020-02-24 13:56 ` Halil Pasic
2020-02-25 3:30 ` Jason Wang
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