Messages in this thread | | | Date | Wed, 07 Jan 2015 06:41:58 +0100 | From | Paolo Bonzini <> | Subject | Re: [RFC 2/2] x86, vdso, pvclock: Simplify and speed up the vdso pvclock reader |
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On 06/01/2015 19:26, Andy Lutomirski wrote: > Don't you stil need: > > version++; > write the rest; > version++; > > with possible smp_wmb() in there to keep the compiler from messing around?
No, see my other reply.
Separating the version write is a real bug, but that should be all that it's needed.
> Also, if you do this, can you also make setting and clearing > STABLE_BIT properly atomic across all vCPUs? Or at least do something > like setting it last and clearing it first on vPCU 0?
That would be nice if you want to make the pvclock area fit in a single page. However, it would have to be a separate flag bit, or a separate CPUID feature.
Paolo
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