From: Srujana Challa <schalla@marvell.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>,
"virtualization@lists.linux.dev" <virtualization@lists.linux.dev>,
"xuanzhuo@linux.alibaba.com" <xuanzhuo@linux.alibaba.com>,
Vamsi Krishna Attunuru <vattunuru@marvell.com>,
Shijith Thotton <sthotton@marvell.com>,
Nithin Kumar Dabilpuram <ndabilpuram@marvell.com>,
Jerin Jacob <jerinj@marvell.com>, eperezma <eperezma@redhat.com>
Subject: RE: [EXTERNAL] Re: [PATCH] virtio: vdpa: vDPA driver for Marvell OCTEON DPU devices
Date: Wed, 10 Apr 2024 12:34:53 +0000 [thread overview]
Message-ID: <DS0PR18MB5368C21CDDE827AA2A496510A0062@DS0PR18MB5368.namprd18.prod.outlook.com> (raw)
In-Reply-To: <20240410071350-mutt-send-email-mst@kernel.org>
> Subject: Re: [EXTERNAL] Re: [PATCH] virtio: vdpa: vDPA driver for Marvell
> OCTEON DPU devices
>
> On Wed, Apr 10, 2024 at 10:15:37AM +0000, Srujana Challa wrote:
> > > > > > +
> > > > > > + domain = iommu_get_domain_for_dev(dev);
> > > > > > + if (!domain || domain->type == IOMMU_DOMAIN_IDENTITY) {
> > > > > > + dev_info(dev, "NO-IOMMU\n");
> > > > > > + octep_vdpa_ops.set_map = octep_vdpa_set_map;
> > > > >
> > > > > Is this a shortcut to have get better performance? DMA API
> > > > > should have those greacefully I think.
> > > > When IOMMU is disabled on host and set_map/dma_map is not set,
> > > > vhost-vdpa is reporting an error "Failed to allocate domain,
> > > > device is not
> > > IOMMU cache coherent capable\n".
> > > > Hence we are doing this way to get better performance.
> > >
> > > The problem is, assuming the device does not have any internal IOMMU.
> > >
> > > 1) If we allow it running without IOMMU, it opens a window for guest
> > > to attack the host.
> > > 2) If you see perforamnce issue with IOMMU_DOMAIN_IDENTITY, let's
> > > report it to DMA/IOMMU maintiner to fix that
> > It will be helpful for host networking case when iommu is disabled.
> > Can we take the vfio pci driver approach as a reference where user
> > explicitly set "enable_unsafe_noiommu_mode" using module param?
>
> vfio is a userspace driver so it's userspace's responsibility.
> what exactly ensures correctness here? does the device have an on-chip
> iommu?
>
Our device features an on-chip IOMMU, although it is not utilized for host-side
targeted DMA operations. We included no-iommu mode in our driver to ensure
that host applications, such as DPDK Virtio user PMD, continue to function even
when operating in a no-IOMMU mode. We observed performance impacts on
certain low-end x86 machines when IOMMU mode was enabled.
I think, correctness is Host userspace application's responsibility, in this case
when vhost-vdpa is used with Host application such as DPDK Virtio user PMD.
> > >
> > > Thanks
> >
> > Thanks.
> >
next prev parent reply other threads:[~2024-04-10 12:35 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-27 11:21 [PATCH] virtio: vdpa: vDPA driver for Marvell OCTEON DPU devices Srujana Challa
2024-03-29 4:28 ` Jason Wang
2024-03-29 12:34 ` [EXTERNAL] " Srujana Challa
2024-03-31 11:31 ` Michael S. Tsirkin
2024-04-07 3:24 ` Jason Wang
2024-04-07 3:34 ` Jason Wang
2024-04-10 10:15 ` Srujana Challa
2024-04-10 11:19 ` Michael S. Tsirkin
2024-04-10 12:34 ` Srujana Challa [this message]
2024-04-11 6:01 ` Jason Wang
2024-04-12 5:12 ` Srujana Challa
2024-04-12 6:41 ` Jason Wang
2024-04-12 9:48 ` Srujana Challa
2024-04-15 6:49 ` Jason Wang
2024-04-15 12:42 ` Srujana Challa
2024-04-16 3:17 ` Jason Wang
2024-04-22 20:42 ` Michael S. Tsirkin
2024-04-24 13:05 ` Srujana Challa
2024-04-23 5:40 ` Srujana Challa
2024-04-11 5:59 ` Jason Wang
2024-03-29 11:37 ` Stefano Garzarella
2024-03-29 13:02 ` [EXTERNAL] " Srujana Challa
2024-03-29 13:19 ` Stefano Garzarella
2024-04-10 12:40 ` Srujana Challa
2024-04-22 20:44 ` Michael S. Tsirkin
2024-04-24 19:08 ` [PATCH v2] " Srujana Challa
2024-04-25 1:57 ` Jason Wang
2024-04-25 9:36 ` Michael S. Tsirkin
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