Re: [PATCH v3 5/9] KVM: MMU: introduce SPTE_WRITE_PROTECT bit

[Xiao Guangrong]

On 04/21/2012 08:55 AM, Marcelo Tosatti wrote:


>> So this is an example of implicit assumptions which break if you update
>> spte without mmu_lock. Certainly there are more cases. :(
> 
> OK, i now see you mentioned a similar case in the document, for
> rmap_write_protect.
> 
> More importantly than the particular flush TLB case, the point is
> every piece of code that reads and writes sptes must now be aware that
> mmu_lock alone does not guarantee stability. Everything must be audited.
> 


Yes, that is true, but it is not hard to audit the code since we only
change the spte from read-only to writable, also all information that
fast page fault depends on is from spte.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/