Re: [Qemu-devel] [PATCH] resent: x86/cpuid: propagate further CPUID leafs when -cpu host

[Avi Kivity]

On 05/25/2010 04:26 PM, Anthony Liguori wrote:
> On 05/25/2010 08:21 AM, Andre Przywara wrote:
> > > What's the benefit of exposing this information to the guest?
> >
> > That is mostly to propagate the cache size and organization 
> > parameters to the guest:
> > >> +/* safe CPUID leafs to propagate to guest if -cpu host is specified
> > >> + * Intel defined leafs:
> > >> + * Cache descriptors (0x02)
> > >> + * Deterministic cache parameters (0x04)
> > >> + * Monitor/MWAIT parameters (0x05)
> > >> + *
> > >> + * AMD defined leafs:
> > >> + * L1 Cache and TLB (0x05)
> > >> + * L2+L3 TLB (0x06)
> > >> + * LongMode address size (0x08)
> > >> + * 1GB page TLB (0x19)
> > >> + * Performance optimization (0x1A)
> > >> + */
> > Since at least L1 and L2 caches are mostly private to vCPUs, I see no 
> > reason to disguise them.
>
> But in practice, what is it useful for? 

See my other mail.

> Just because we can expose it doesn't mean we should.

What's the point of -cpu host then?

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