Re: [PATCH] vfio powerpc: enabled on powernv platform

[Alexey Kardashevskiy]

On 29/11/12 15:20, Alex Williamson wrote:

> > +	/* Put tces to the table */
> > +	for (i = 0; (i < pages) && !ret; ++i, tce += IOMMU_PAGE_SIZE) {
> > +		ret = put_tce(tbl, entry + i, tce, direction);
> > +		/*
> > +		 * As IOMMU page size is always 4K, the system page size
> > +		 * can be 64K and there is no special tracking for IOMMU pages,
> > +		 * we only do rlimit check/update for the very first
> > +		 * 4K IOMMUpage within 64K system page.
> > +		 */
> > +		if (!(tce & ~PAGE_MASK))
> > +			++retpages;
>
> Ah, here's the comment I was looking for, though I'm still not sure
> about the read/write bits.
>
> Isn't there an exploit here that a user can lock pages beyond their
> limits if they just skip mapping the first 4k of each page?  Thanks,


Heh. True. Posted another patch with 4K pages per system page usage tracking.



--
Alexey
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