From: "Michael S. Tsirkin" <mst@redhat.com>
To: Halil Pasic <pasic@linux.ibm.com>
Cc: Jason Wang <jasowang@redhat.com>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Robin Murphy <robin.murphy@arm.com>,
Christoph Hellwig <hch@lst.de>,
linux-s390@vger.kernel.org,
virtualization@lists.linux-foundation.org,
linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
Christian Borntraeger <borntraeger@de.ibm.com>,
Janosch Frank <frankja@linux.ibm.com>,
Viktor Mihajlovski <mihajlov@linux.ibm.com>,
Cornelia Huck <cohuck@redhat.com>, Ram Pai <linuxram@us.ibm.com>,
Thiago Jung Bauermann <bauerman@linux.ibm.com>,
David Gibson <david@gibson.dropbear.id.au>,
"Lendacky, Thomas" <Thomas.Lendacky@amd.com>,
Michael Mueller <mimu@linux.ibm.com>
Subject: Re: [PATCH 0/2] virtio: decouple protected guest RAM form VIRTIO_F_IOMMU_PLATFORM
Date: Thu, 20 Feb 2020 16:33:35 -0500 [thread overview]
Message-ID: <20200220163055-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20200220160606.53156-1-pasic@linux.ibm.com>
On Thu, Feb 20, 2020 at 05:06:04PM +0100, Halil Pasic wrote:
> For vhost-net the feature VIRTIO_F_IOMMU_PLATFORM has the following side
> effect The vhost code assumes it the addresses on the virtio descriptor
> ring are not guest physical addresses but iova's, and insists on doing a
> translation of these regardless of what transport is used (e.g. whether
> we emulate a PCI or a CCW device). (For details see commit 6b1e6cc7855b
> "vhost: new device IOTLB API".) On s390 this results in severe
> performance degradation (c.a. factor 10). BTW with ccw I/O there is
> (architecturally) no IOMMU, so the whole address translation makes no
> sense in the context of virtio-ccw.
So it sounds like a host issue: the emulation of s390 unnecessarily complicated.
Working around it by the guest looks wrong ...
> Halil Pasic (2):
> mm: move force_dma_unencrypted() to mem_encrypt.h
> virtio: let virtio use DMA API when guest RAM is protected
>
> drivers/virtio/virtio_ring.c | 3 +++
> include/linux/dma-direct.h | 9 ---------
> include/linux/mem_encrypt.h | 10 ++++++++++
> 3 files changed, 13 insertions(+), 9 deletions(-)
>
>
> base-commit: ca7e1fd1026c5af6a533b4b5447e1d2f153e28f2
> --
> 2.17.1
next prev parent reply other threads:[~2020-02-20 21:33 UTC|newest]
Thread overview: 57+ 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
[not found] ` <691d8c8e-665c-b05f-383f-78377fcf6741@amazon.com>
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 [this message]
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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