Re: [PATCH kernel v7 04/31] vfio: powerpc/spapr: Use it_page_size

[Alexey Kardashevskiy]

On 04/02/2015 08:48 AM, Alex Williamson wrote:
> On Sat, 2015-03-28 at 01:54 +1100, Alexey Kardashevskiy wrote:
> > This makes use of the it_page_size from the iommu_table struct
> > as page size can differ.
> >
> > This replaces missing IOMMU_PAGE_SHIFT macro in commented debug code
> > as recently introduced IOMMU_PAGE_XXX macros do not include
> > IOMMU_PAGE_SHIFT.
> >
> > Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
> > Reviewed-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
> > ---
> >   drivers/vfio/vfio_iommu_spapr_tce.c | 26 +++++++++++++-------------
> >   1 file changed, 13 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> > index f835e63..8bbee22 100644
> > --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> > +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> > @@ -91,7 +91,7 @@ static int tce_iommu_enable(struct tce_container *container)
> >   	 * enforcing the limit based on the max that the guest can map.
> >   	 */
> >   	down_write(&current->mm->mmap_sem);
> > -	npages = (tbl->it_size << IOMMU_PAGE_SHIFT_4K) >> PAGE_SHIFT;
> > +	npages = (tbl->it_size << tbl->it_page_shift) >> PAGE_SHIFT;
> >   	locked = current->mm->locked_vm + npages;
> >   	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> >   	if (locked > lock_limit && !capable(CAP_IPC_LOCK)) {
> > @@ -120,7 +120,7 @@ static void tce_iommu_disable(struct tce_container *container)
> >
> >   	down_write(&current->mm->mmap_sem);
> >   	current->mm->locked_vm -= (container->tbl->it_size <<
> > -			IOMMU_PAGE_SHIFT_4K) >> PAGE_SHIFT;
> > +			container->tbl->it_page_shift) >> PAGE_SHIFT;
> >   	up_write(&current->mm->mmap_sem);
> >   }
> >
> > @@ -222,7 +222,7 @@ static long tce_iommu_build(struct tce_container *container,
> >   					tce, ret);
> >   			break;
> >   		}
> > -		tce += IOMMU_PAGE_SIZE_4K;
> > +		tce += IOMMU_PAGE_SIZE(tbl);
>
>
> Is PAGE_SIZE ever smaller than IOMMU_PAGE_SIZE(tbl)?  IOW, can the page
> we got from get_user_pages_fast() ever not completely fill the tce
> entry?


Yes. IOMMU_PAGE_SIZE is 4K/64K/16M (16M is with huge pages enabled in QEMU 
with -mempath), PAGE_SIZE is 4K/64K (normally 64K).


> (Have I asked this before?  Sorry if so)


:)



--
Alexey
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