RE: [RFC v2 1/3] vfio: VFIO_IOMMU_CACHE_INVALIDATE

Liu, Yi L
2019-11-06T01:31:44Z

> From: Alex Williamson [mailto:alex.williamson@redhat.com]
> Sent: Wednesday, November 6, 2019 6:42 AM
> To: Liu, Yi L <yi.l.liu@intel.com>
> Subject: Re: [RFC v2 1/3] vfio: VFIO_IOMMU_CACHE_INVALIDATE
>
> On Fri, 25 Oct 2019 11:20:40 +0000
> "Liu, Yi L" <yi.l.liu@intel.com> wrote:
>
> > Hi Kevin,
> >
> > > From: Tian, Kevin
> > > Sent: Friday, October 25, 2019 5:14 PM
> > > To: Liu, Yi L <yi.l.liu@intel.com>; alex.williamson@redhat.com;
> > > Subject: RE: [RFC v2 1/3] vfio: VFIO_IOMMU_CACHE_INVALIDATE
> > >
> > > > From: Liu, Yi L
> > > > Sent: Thursday, October 24, 2019 8:26 PM
> > > >
> > > > From: Liu Yi L <yi.l.liu@linux.intel.com>
> > > >
> > > > When the guest "owns" the stage 1 translation structures, the
> > > > host IOMMU driver has no knowledge of caching structure updates
> > > > unless the guest invalidation requests are trapped and passed down to the host.
> > > >
> > > > This patch adds the VFIO_IOMMU_CACHE_INVALIDATE ioctl with aims at
> > > > propagating guest stage1 IOMMU cache invalidations to the host.
> > > >
> > > > Cc: Kevin Tian <kevin.tian@intel.com>
> > > > Signed-off-by: Liu Yi L <yi.l.liu@linux.intel.com>
> > > > Signed-off-by: Eric Auger <eric.auger@redhat.com>
> > > > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > > > ---
> > > > drivers/vfio/vfio_iommu_type1.c | 55
> > > > +++++++++++++++++++++++++++++++++++++++++
> > > > include/uapi/linux/vfio.h | 13 ++++++++++
> > > > 2 files changed, 68 insertions(+)
> > > >
> > > > diff --git a/drivers/vfio/vfio_iommu_type1.c
> > > > b/drivers/vfio/vfio_iommu_type1.c index 96fddc1d..cd8d3a5 100644
> > > > --- a/drivers/vfio/vfio_iommu_type1.c
> > > > +++ b/drivers/vfio/vfio_iommu_type1.c
> > > > @@ -124,6 +124,34 @@ struct vfio_regions {
> > > > #define IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu) \
> > > > (!list_empty(&iommu->domain_list))
> > > >
> > > > +struct domain_capsule {
> > > > + struct iommu_domain *domain;
> > > > + void *data;
> > > > +};
> > > > +
> > > > +/* iommu->lock must be held */
> > > > +static int
> > > > +vfio_iommu_lookup_dev(struct vfio_iommu *iommu,
> > > > + int (*fn)(struct device *dev, void *data),
> > > > + void *data)
> > >
> > > 'lookup' usually means find a device and then return. But the real
> > > purpose here is to loop all the devices within this container and
> > > then do something. Does it make more sense to be vfio_iommu_for_each_dev?
>
> +1
>
> > yep, I can replace it.
> >
> > >
> > > > +{
> > > > + struct domain_capsule dc = {.data = data};
> > > > + struct vfio_domain *d;
> > [...]
> > > 2315,6 +2352,24 @@
> > > > static long vfio_iommu_type1_ioctl(void *iommu_data,
> > > >
> > > > return copy_to_user((void __user *)arg, &unmap, minsz) ?
> > > > -EFAULT : 0;
> > > > + } else if (cmd == VFIO_IOMMU_CACHE_INVALIDATE) {
> > > > + struct vfio_iommu_type1_cache_invalidate ustruct;
> > >
> > > it's weird to call a variable as struct.
> >
> > Will fix it.
> >
> > > > + int ret;
> > > > +
> > > > + minsz = offsetofend(struct
> > > > vfio_iommu_type1_cache_invalidate,
> > > > + info);
> > > > +
> > > > + if (copy_from_user(&ustruct, (void __user *)arg, minsz))
> > > > + return -EFAULT;
> > > > +
> > > > + if (ustruct.argsz < minsz || ustruct.flags)
> > > > + return -EINVAL;
> > > > +
> > > > + mutex_lock(&iommu->lock);
> > > > + ret = vfio_iommu_lookup_dev(iommu, vfio_cache_inv_fn,
> > > > + &ustruct);
> > > > + mutex_unlock(&iommu->lock);
> > > > + return ret;
> > > > }
> > > >
> > > > return -ENOTTY;
> > > > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> > > > index 9e843a1..ccf60a2 100644
> > > > --- a/include/uapi/linux/vfio.h
> > > > +++ b/include/uapi/linux/vfio.h
> > > > @@ -794,6 +794,19 @@ struct vfio_iommu_type1_dma_unmap {
> > > > #define VFIO_IOMMU_ENABLE _IO(VFIO_TYPE, VFIO_BASE + 15)
> > > > #define VFIO_IOMMU_DISABLE _IO(VFIO_TYPE, VFIO_BASE + 16)
> > > >
> > > > +/**
> > > > + * VFIO_IOMMU_CACHE_INVALIDATE - _IOWR(VFIO_TYPE, VFIO_BASE +
> > > > 24,
>
> What's going on with these ioctl numbers? AFAICT[1] we've used up through
> VFIO_BASE + 21, this jumps to 24, the next patch skips to 27, then the last patch fills
> in 28 & 29. Thanks,

Hi Alex,

I rebase my patch to Eric's nested stage translation patches. His base also introduced
IOCTLs. I should have made it better. I'll try to sync with Eric to serialize the IOCTLs.

[PATCH v6 00/22] SMMUv3 Nested Stage Setup by Eric Auger
https://lkml.org/lkml/2019/3/17/124

Thanks,
Yi Liu

> Alex
>
> [1] git grep -h VFIO_BASE | grep "VFIO_BASE +" | grep -e ^#define | \
> awk '{print $NF}' | tr -d ')' | sort -u -n