Re: [PATCH v2 2/2] x86/mm: implement free pmd/pte page interfaces

[Chintan Pandya <cpandya@codeaurora.org>]

On 4/27/2018 6:18 PM, joro@8bytes.org wrote:
> On Fri, Apr 27, 2018 at 05:22:28PM +0530, Chintan Pandya wrote:
>> I'm bit confused here. Are you pointing to race within ioremap/vmalloc
>> framework while updating the page table or race during tlb ops. Since
>> later is arch dependent, I would not comment. But if the race being
>> discussed here while altering page tables, I'm not on the same page.
> 
> The race condition is between hardware and software. It is not
> sufficient to just remove the software references to the page that is
> about to be freed (by clearing the PMD/PUD), also the hardware
> references in the page-walk cache need to be removed with a TLB flush.
> Otherwise the hardware can use the freed (and possibly reused) page to
> establish new TLB entries.

Sure ! This is my understanding too (from arm64 context).

> 
> 
> 
> 	Joerg
> 
> 
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Chintan
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