Re: [PATCH 7/7] KVM: MMU: cache guest page number to guest framenumber

From: Avi Kivity
Date: Wed Feb 23 2011 - 04:28:27 EST


On 02/23/2011 03:38 AM, Xiao Guangrong wrote:
On 02/22/2011 10:32 PM, Avi Kivity wrote:
> On 02/22/2011 10:16 AM, Xiao Guangrong wrote:
>> Cache guest page number to guest frame number to avoid walk guest page table
>> frequently, the 'vtlb' idea is from Xen.
>>
>> Note:
>> we can't use vtlb in ept guests since the guest tlb invalid operation is not
>> intercept(reload CR3, invlpg), also can't used in L2 nnpt guest for the same
>> reason, but we can used it to cache L1's npt page table.
>>
>
> I'm not so hot about introducing a new mechanism strictly for older hosts... EPT exists in three generations of Intel processors now (Sandy Bridge, Westmere, and Nehalem), and NPT is significantly older.
>

Um...so, do we should stop the new features for softmmu, only bug fix is welcome? :-)

No. There is always a tradeoff between features and complexity. What I'm saying is that I want to shift the tradeoff, for older processors, towards reducing complexity. An improvement that is very simple, or gives very large gains, will be accepted. A complex improvement that gives small gains may be rejected (but if it's for newer processors, it may be accepted). It's a way for the maintainers to manage the ever growing complexity.

--
error compiling committee.c: too many arguments to function

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