[PATCH v2 00/16] KVM: MMU: fast page fault

From: Xiao Guangrong
Date: Fri Apr 13 2012 - 06:05:40 EST


Thanks for Avi and Marcelo's review, i have simplified the whole things
in this version:
- it only fix the page fault with PFEC.P = 1 && PFEC.W = 0 that means
unlock set_spte path can be dropped.

- it only fixes the page fault caused by dirty-log

In this version, all the information we need is from spte, the
SPTE_ALLOW_WRITE bit and SPTE_WRITE_PROTECT bit:
- SPTE_ALLOW_WRITE is set if the gpte is writable and the pfn pointed
by the spte is writable on host.
- SPTE_WRITE_PROTECT is set if the spte is write-protected by shadow
page table protection.

All these bits can be protected by cmpxchg, now, all the things is fairly
simple than before. :)

Performance test:

autotest migration:
(Host: Intel(R) Xeon(R) CPU X5690 @ 3.47GHz * 12 + 32G)

- For ept:

Before:
smp2.Fedora.16.64.migrate
Times .unix .with_autotest.dbench.unix total
1 104 214 323
2 68 238 310
3 68 242 314

After:
smp2.Fedora.16.64.migrate
Times .unix .with_autotest.dbench.unix total
1 101 190 295
2 67 188 259
3 66 217 289


- For shadow mmu:

Before:
smp2.Fedora.16.64.migrate
Times .unix .with_autotest.dbench.unix total
1 103 235 342
2 64 219 286
3 68 234 305

After:
smp2.Fedora.16.64.migrate
Times .unix .with_autotest.dbench.unix total
1 104 220 328
2 65 204 273
3 64 219 286

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