Re: [PATCH] vfio powerpc: implement IOMMU driver for VFIO

[Alexey Kardashevskiy]

On 21/03/13 07:45, Alex Williamson wrote:
> On Tue, 2013-03-19 at 18:08 +1100, Alexey Kardashevskiy wrote:
> > VFIO implements platform independent stuff such as
> > a PCI driver, BAR access (via read/write on a file descriptor
> > or direct mapping when possible) and IRQ signaling.
> >
> > The platform dependent part includes IOMMU initialization
> > and handling. This patch implements an IOMMU driver for VFIO
> > which does mapping/unmapping pages for the guest IO and
> > provides information about DMA window (required by a POWERPC
> > guest).
> >
> > The counterpart in QEMU is required to support this functionality.
> >
> > Changelog:
> > * documentation updated
> > * containter enable/disable ioctls added
> > * request_module(spapr_iommu) added
> > * various locks fixed
> >
> > Cc: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
> > ---
>
>
> Looking pretty good.  There's one problem with the detach_group,
> otherwise just some trivial comments below.  What's the status of the
> tce code that this depends on?  Thanks,


It is done, I am just waiting till other patches of the series will be 
reviewed (by guys) and fixed (by me) and then I'll post everything again.

[skipped]

> > +static int tce_iommu_enable(struct tce_container *container)
> > +{
> > +	int ret = 0;
> > +	unsigned long locked, lock_limit, npages;
> > +	struct iommu_table *tbl = container->tbl;
> > +
> > +	if (!container->tbl)
> > +		return -ENXIO;
> > +
> > +	if (!current->mm)
> > +		return -ESRCH; /* process exited */
> > +
> > +	mutex_lock(&container->lock);
> > +	if (container->enabled) {
> > +		mutex_unlock(&container->lock);
> > +		return -EBUSY;
> > +	}
> > +
> > +	/*
> > +	 * Accounting for locked pages.
> > +	 *
> > +	 * On sPAPR platform, IOMMU translation table contains
> > +	 * an entry per 4K page. Every map/unmap request is sent
> > +	 * by the guest via hypercall and supposed to be handled
> > +	 * quickly, ecpesially in real mode (if such option is
>
> s/ecpesially/especially/


I replaced the whole text by the one written by Ben and David.

[skipped]

> > +	}
> > +
> > +	return -ENOTTY;
> > +}
> > +
> > +static int tce_iommu_attach_group(void *iommu_data,
> > +		struct iommu_group *iommu_group)
> > +{
> > +	int ret;
> > +	struct tce_container *container = iommu_data;
> > +	struct iommu_table *tbl = iommu_group_get_iommudata(iommu_group);
> > +
> > +	BUG_ON(!tbl);
> > +	mutex_lock(&container->lock);
> > +	pr_debug("tce_vfio: Attaching group #%u to iommu %p\n",
> > +			iommu_group_id(iommu_group), iommu_group);
> > +	if (container->tbl) {
> > +		pr_warn("tce_vfio: Only one group per IOMMU container is allowed, existing id=%d, attaching id=%d\n",
> > +				iommu_group_id(container->tbl->it_group),
> > +				iommu_group_id(iommu_group));
> > +		mutex_unlock(&container->lock);
> > +		return -EBUSY;
> > +	}
> > +
> > +	ret = iommu_take_ownership(tbl);
> > +	if (!ret)
> > +		container->tbl = tbl;
> > +
> > +	mutex_unlock(&container->lock);
> > +
> > +	return ret;
> > +}
> > +
> > +static void tce_iommu_detach_group(void *iommu_data,
> > +		struct iommu_group *iommu_group)
> > +{
> > +	struct tce_container *container = iommu_data;
> > +	struct iommu_table *tbl = iommu_group_get_iommudata(iommu_group);
> > +
> > +	BUG_ON(!tbl);
> > +	mutex_lock(&container->lock);
> > +	if (tbl != container->tbl) {
> > +		pr_warn("tce_vfio: detaching group #%u, expected group is #%u\n",
> > +				iommu_group_id(iommu_group),
> > +				iommu_group_id(tbl->it_group));
> > +	} else if (container->enabled) {
> > +		pr_err("tce_vfio: detaching group #%u from enabled container\n",
> > +				iommu_group_id(tbl->it_group));
>
> Hmm, something more than a pr_err needs to happen here.  Wouldn't this
> imply a disable and going back to an unprivileged container?

Ah. It does not return error code... Then something like that?

...
         } else if (container->enabled) {
                 pr_warn("tce_vfio: detaching group #%u from enabled 
container, forcing disable\n",
                                 iommu_group_id(tbl->it_group));
                 tce_iommu_disable(container);
...

--
Alexey
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