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

From: Avi Kivity
Date: Tue Feb 22 2011 - 09:32:36 EST


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.

I'd rather make the guest page table walk faster. I believe that things like get_user() can be significantly faster than copy_from_user() on older hosts, and a four-level page table walk shouldn't be that slow.

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

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