Re: [PATCH kernel v10 11/34] vfio: powerpc/spapr: Moving pinning/unpinning to helpers

[Alexey Kardashevskiy]

On 05/13/2015 04:32 PM, Gavin Shan wrote:
> On Tue, May 12, 2015 at 01:39:00AM +1000, Alexey Kardashevskiy wrote:
> > This is a pretty mechanical patch to make next patches simpler.
> >
> > New tce_iommu_unuse_page() helper does put_page() now but it might skip
> > that after the memory registering patch applied.
> >
> > As we are here, this removes unnecessary checks for a value returned
> > by pfn_to_page() as it cannot possibly return NULL.
> >
> > This moves tce_iommu_disable() later to let tce_iommu_clear() know if
> > the container has been enabled because if it has not been, then
> > put_page() must not be called on TCEs from the TCE table. This situation
> > is not yet possible but it will after KVM acceleration patchset is
> > applied.
> >
> > This changes code to work with physical addresses rather than linear
> > mapping addresses for better code readability. Following patches will
> > add an xchg() callback for an IOMMU table which will accept/return
> > physical addresses (unlike current tce_build()) which will eliminate
> > redundant conversions.
> >
> > Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
> > [aw: for the vfio related changes]
> > Acked-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> > Reviewed-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
>
> Reviewed-by: Gavin Shan <gwshan@xxxxxxxxxxxxxxxxxx>
>
> > ---
> > Changes:
> > v9:
> > * changed helpers to work with physical addresses rather than linear
> > (for simplicity - later ::xchg() will receive physical and avoid
> > additional convertions)
> >
> > v6:
> > * tce_get_hva() returns hva via a pointer
> > ---
> > drivers/vfio/vfio_iommu_spapr_tce.c | 61 +++++++++++++++++++++++++------------
> > 1 file changed, 41 insertions(+), 20 deletions(-)
> >
> > diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> > index e21479c..115d5e6 100644
> > --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> > +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> > @@ -191,69 +191,90 @@ static void tce_iommu_release(void *iommu_data)
> > 	struct tce_container *container = iommu_data;
> >
> > 	WARN_ON(container->tbl && !container->tbl->it_group);
> > -	tce_iommu_disable(container);
> >
> > 	if (container->tbl && container->tbl->it_group)
> > 		tce_iommu_detach_group(iommu_data, container->tbl->it_group);
> >
> > +	tce_iommu_disable(container);
> > 	mutex_destroy(&container->lock);
> >
> > 	kfree(container);
> > }
> >
> > +static void tce_iommu_unuse_page(struct tce_container *container,
> > +		unsigned long oldtce)
> > +{
> > +	struct page *page;
> > +
> > +	if (!(oldtce & (TCE_PCI_READ | TCE_PCI_WRITE)))
> > +		return;
> > +
>
> It might be worthy to have a global helper function in iommu.h to check
> if the given TCE entry is empty or not, for better readability. I would
> think the helper function is used here and there :-)

The patchset adds one later, called iommu_tce_direction() ;)

In general, I removed TCE_PCI_READ, TCE_PCI_WRITE from everywhere but 
powernv code and used  enum dma_data_direction instead as these bits are 
SPAPR TCE protocol specific and VFIO IOMMU API or 
arch/powerpc/kernel/iommu.c do not receive/handle these bits, they have 
their own, platform independent.


--
Alexey
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