[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [PATCH] resent: x86/cpuid: propagate further CPUID leaf

From: Anthony Liguori
Subject: Re: [Qemu-devel] [PATCH] resent: x86/cpuid: propagate further CPUID leafs when -cpu host
Date: Tue, 25 May 2010 08:26:08 -0500
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20091209 Fedora/3.0-4.fc12 Lightning/1.0pre Thunderbird/3.0

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


Anthony Liguori


reply via email to

[Prev in Thread] Current Thread [Next in Thread]