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Re: [PATCH v1 15/22] Add iommufd configure option
From: |
Jason Gunthorpe |
Subject: |
Re: [PATCH v1 15/22] Add iommufd configure option |
Date: |
Wed, 20 Sep 2023 09:51:03 -0300 |
On Wed, Sep 20, 2023 at 02:19:42PM +0200, Cédric Le Goater wrote:
> On 9/20/23 05:42, Duan, Zhenzhong wrote:
> >
> >
> > > -----Original Message-----
> > > From: Cédric Le Goater <clg@redhat.com>
> > > Sent: Wednesday, September 20, 2023 1:08 AM
> > > Subject: Re: [PATCH v1 15/22] Add iommufd configure option
> > >
> > > On 8/30/23 12:37, Zhenzhong Duan wrote:
> > > > This adds "--enable-iommufd/--disable-iommufd" to enable or disable
> > > > iommufd support, enabled by default.
> > >
> > > Why would someone want to disable support at compile time ? It might
> >
> > For those users who only want to support legacy container feature?
> > Let me know if you still prefer to drop this patch, I'm fine with that.
>
> I think it is too early.
>
> > > have been useful for dev but now QEMU should self-adjust at runtime
> > > depending only on the host capabilities AFAIUI. Am I missing something ?
> >
> > IOMMUFD doesn't support all features of legacy container, so QEMU
> > doesn't self-adjust at runtime by checking if host supports IOMMUFD.
> > We need to specify it explicitly to use IOMMUFD as below:
> >
> > -object iommufd,id=iommufd0
> > -device vfio-pci,host=0000:02:00.0,iommufd=iommufd0
>
> OK. I am not sure this is the correct interface yet. At first glance,
> I wouldn't introduce a new object for a simple backend depending on a
> kernel interface. I would tend to prefer a "iommu-something" property
> of the vfio-pci device with string values: "legacy", "iommufd", "default"
> and define the various interfaces (the ops you proposed) for each
> depending on the user preference and the capabilities of the host and
> possibly the device.
I think the idea came from Alex? The major point is to be able to have
libvirt open /dev/iommufd and FD pass it into qemu and then share that
single FD across all VFIOs. qemu will typically not be able to
self-open /dev/iommufd as it is root-only.
So the object is not exactly for the backend, the object is for the
file descriptor.
Adding a legacy/iommufd option to the vfio-pci device string doesn't
address these needs.
Jason
- Re: [PATCH v1 15/22] Add iommufd configure option, Cédric Le Goater, 2023/09/19
- RE: [PATCH v1 15/22] Add iommufd configure option, Duan, Zhenzhong, 2023/09/19
- Re: [PATCH v1 15/22] Add iommufd configure option, Cédric Le Goater, 2023/09/20
- Re: [PATCH v1 15/22] Add iommufd configure option, Cédric Le Goater, 2023/09/20
- Re: [PATCH v1 15/22] Add iommufd configure option, Eric Auger, 2023/09/20
- Re: [PATCH v1 15/22] Add iommufd configure option, Jason Gunthorpe, 2023/09/20
- Re: [PATCH v1 15/22] Add iommufd configure option, Alex Williamson, 2023/09/20
- Re: [PATCH v1 15/22] Add iommufd configure option, Jason Gunthorpe, 2023/09/20
- RE: [PATCH v1 15/22] Add iommufd configure option, Duan, Zhenzhong, 2023/09/20
- RE: [PATCH v1 15/22] Add iommufd configure option, Tian, Kevin, 2023/09/26
- RE: [PATCH v1 15/22] Add iommufd configure option, Duan, Zhenzhong, 2023/09/21