From: Jason Gunthorpe <jgg@nvidia.com>
To: Nicolin Chen <nicolinc@nvidia.com>
Cc: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>,
"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
Linuxarm <linuxarm@huawei.com>,
Zhangfei Gao <zhangfei.gao@linaro.org>,
Michael Shavit <mshavit@google.com>,
Eric Auger <eric.auger@redhat.com>,
Moritz Fischer <mdf@kernel.org>
Subject: Re: Query on ARM SMMUv3 nested support
Date: Mon, 18 Mar 2024 13:22:14 -0300 [thread overview]
Message-ID: <20240318162214.GC5825@nvidia.com> (raw)
In-Reply-To: <ZfI74miZ1ss9+Kz0@Asurada-Nvidia>
On Wed, Mar 13, 2024 at 04:50:58PM -0700, Nicolin Chen wrote:
> On Wed, Mar 13, 2024 at 10:13:58AM +0000, Shameerali Kolothum Thodi wrote:
> > Hi Nicolin,
> >
> > Thanks for the latest repos with basic SMMUv3 nested support enabled[1].
> > I did some basic sanity runs on a HiSilicon platform and they seems to work as
> > expected. The only problem being we can't assign two devices to the VM if
> > they are on different physical SMMUs.
> >
> > qemu-system-aarch64: -device
> > vfio-pci,host=0000:75:00.1,iommufd=iommufd0: [iommufd=29] error attach
> > 0000:75:00.1 (36) to id=4: Invalid argument
> > qemu-system-aarch64: -device
> > vfio-pci,host=0000:75:00.1,iommufd=iommufd0: Unable to attach dev to
> > stage-2 HW pagetable: -1
> > Segmentation fault (core dumped)
> > ...
> >
> > I see that on the Qemu side we now allocate a single s2 hwpt and attach that into
> > all the devices . But this will only work currently if all the assigned devices
> > are under the same physical SMMUv3 as we have a check in kernel
> > whether domains are having the same SMMUv3. I remember Jason mentioning
> > that he is planning to relax that.
Yes, I intend this to be the direction as it makes the most sense
> > So are the Qemu side changes based on that assumption? And any
> > idea how we are planning to relax that restriction? We do a check
> > for compatibility of the phys SMMUv3s and then allow/restrict in
> > kernel?
Right, so qemu should still handle the case where the HWPT is not
compatible and create a new HWPT. Regardless of the kernel side
optimization qemu is still missing this logic apparently.
> > Do Qemu can then try allocating a separate s2 hwpt for
> > those and attach again? Sorry if this was already discussed
> > elsewhere and I missed that.
Yes, this is the right thing.
Jason
next prev parent reply other threads:[~2024-03-18 16:22 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-13 10:13 Query on ARM SMMUv3 nested support Shameerali Kolothum Thodi
2024-03-13 23:50 ` Nicolin Chen
2024-03-18 16:22 ` Jason Gunthorpe [this message]
2024-03-22 15:04 ` Shameerali Kolothum Thodi
2024-03-29 7:13 ` Nicolin Chen
2024-04-02 7:25 ` Shameerali Kolothum Thodi
2024-04-02 11:28 ` Jason Gunthorpe
2024-04-09 6:12 ` Nicolin Chen
2024-04-09 19:47 ` Nicolin Chen
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