Re: [Xen-devel] [PATCH] "lock cmpxch8b" and split locks

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 5 Oct 2005, at 22:46, Keir Fraser wrote:

> > Does anyone know if there are other places where the "lock" prefix is
> > used with a cache misaligned address?
> x86 systems are supposed to guarantee that LOCKed instructions access 
> their memory operand atomically, regardless of alignment (Vol 3 of the 
> Intel reference manual). Your systems break this application-visible 
> guarantee?
Also, the patch is way bigger and more invasive than it needs to be. 
There should be no need to make pfn_info bigger than it is. It's 
currently a multiple of 8 bytes (e.g., 24 bytes on 32-bit) which is 
sufficient to avoid cache-line crossing of aligned 8-byte quantities.
What if we just move 'tlbflush_timestamp' to the end of the structure? 
A one-line fix? :-)
 -- Keir


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