Re: [PATCH kernel v6 26/29] vfio: powerpc/spapr: Define v2 IOMMU

[Alexey Kardashevskiy]

On 03/17/2015 06:45 AM, Alex Williamson wrote:
> On Fri, 2015-03-13 at 19:07 +1100, Alexey Kardashevskiy wrote:
> > The existing IOMMU requires VFIO_IOMMU_ENABLE call to enable actual use
> > of the container (i.e. call DMA map/unmap) and this is where we check
> > the rlimit for locked pages. It assumes that only as much memory
> > as a default DMA window can be mapped. Every DMA map/unmap request will
> > do pinning/unpinning of physical pages.
> >
> > New IOMMU will split physical pages pinning and TCE table update.
> > It will require guest pages to be registered first and consequent
> > map/unmap requests to work only with pre-registered memory.
> > For the default single window case this means that the entire guest
> > (instead of 2GB) needs to be pinned before using VFIO.
> > However when a huge DMA window is added, no additional pinning will be
> > required, otherwise it would be guest RAM + 2GB.
> >
> > This advertises v2 SPAPR TCE IOMMU and restricts what the userspace
> > can do with v1 or v2 IOMMUs.
> >
> > Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
> > ---
> > Changes:
> > v6:
> > * enforced limitations imposed by the SPAPR TCE IOMMU version
> > ---
> >   drivers/vfio/vfio_iommu_spapr_tce.c | 18 +++++++++++++++++-
> >   include/uapi/linux/vfio.h           |  2 ++
> >   2 files changed, 19 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> > index 9d240b4..e191438 100644
> > --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> > +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> > @@ -95,6 +95,7 @@ struct tce_container {
> >   	bool enabled;
> >   	unsigned long locked_pages;
> >   	struct list_head mem_list;
> > +	bool v2;
> >   };
> >
> >   struct tce_memory {
> > @@ -398,7 +399,7 @@ static void *tce_iommu_open(unsigned long arg)
> >   {
> >   	struct tce_container *container;
> >
> > -	if (arg != VFIO_SPAPR_TCE_IOMMU) {
> > +	if ((arg != VFIO_SPAPR_TCE_IOMMU) && (arg != VFIO_SPAPR_TCE_v2_IOMMU)) {
> >   		pr_err("tce_vfio: Wrong IOMMU type\n");
> >   		return ERR_PTR(-EINVAL);
> >   	}
> > @@ -410,6 +411,8 @@ static void *tce_iommu_open(unsigned long arg)
> >   	mutex_init(&container->lock);
> >   	INIT_LIST_HEAD_RCU(&container->mem_list);
> >
> > +	container->v2 = arg == VFIO_SPAPR_TCE_v2_IOMMU;
> > +
> >   	return container;
> >   }
> >
> > @@ -580,6 +583,7 @@ static long tce_iommu_ioctl(void *iommu_data,
> >   	case VFIO_CHECK_EXTENSION:
> >   		switch (arg) {
> >   		case VFIO_SPAPR_TCE_IOMMU:
> > +		case VFIO_SPAPR_TCE_v2_IOMMU:
> >   			ret = 1;
> >   			break;
> >   		default:
> > @@ -719,6 +723,9 @@ static long tce_iommu_ioctl(void *iommu_data,
> >   	case VFIO_IOMMU_SPAPR_REGISTER_MEMORY: {
> >   		struct vfio_iommu_spapr_register_memory param;
> >
> > +		if (!container->v2)
> > +			return -EPERM;
> > +
> >   		minsz = offsetofend(struct vfio_iommu_spapr_register_memory,
> >   				size);
> >
> > @@ -741,6 +748,9 @@ static long tce_iommu_ioctl(void *iommu_data,
> >   	case VFIO_IOMMU_SPAPR_UNREGISTER_MEMORY: {
> >   		struct vfio_iommu_spapr_register_memory param;
> >
> > +		if (!container->v2)
> > +			return -EPERM;
> > +
> >   		minsz = offsetofend(struct vfio_iommu_spapr_register_memory,
> >   				size);
> >
> > @@ -761,6 +771,9 @@ static long tce_iommu_ioctl(void *iommu_data,
> >   		return 0;
> >   	}
> >   	case VFIO_IOMMU_ENABLE:
> > +		if (container->v2)
> > +			return -EPERM;
> > +
> >   		mutex_lock(&container->lock);
> >   		ret = tce_iommu_enable(container);
> >   		mutex_unlock(&container->lock);
> > @@ -768,6 +781,9 @@ static long tce_iommu_ioctl(void *iommu_data,
> >
> >
> >   	case VFIO_IOMMU_DISABLE:
> > +		if (container->v2)
> > +			return -EPERM;
> > +
> >   		mutex_lock(&container->lock);
> >   		tce_iommu_disable(container);
> >   		mutex_unlock(&container->lock);
>
>
> I wouldn't have guessed; nothing in the documentation suggests these
> ioctls are deprecated in v2 (ie. please document).  If the ioctl doesn't
> exist for the IOMMU type, why not simply break and let it fall out at
> -ENOTTY?  Same for the above, v1 would have previously returned -ENOTTY
> for those ioctls, why change to -EPERM?


Good points. I'll fix them and merge this patch to "vfio: powerpc/spapr: 
Register memory" as this is where it actually belongs to. Agree?


Thanks for the review!


--
Alexey
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/