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

From: Alexey Kardashevskiy <[email-masked]>
Date: Fri, 30 Nov 2012 17:16:46 +1100

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