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  1. 22 3月, 2013 1 次提交
  3. 13 3月, 2013 1 次提交
  5. 20 9月, 2012 3 次提交
    • A
      KVM: MMU: Optimize is_last_gpte() · 6fd01b71
      由 Avi Kivity 提交于 
      Instead of branchy code depending on level, gpte.ps, and mmu configuration,
prepare everything in a bitmap during mode changes and look it up during
runtime.
Reviewed-by: NXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>
      6fd01b71
    • A
      KVM: MMU: Optimize pte permission checks · 97d64b78
      由 Avi Kivity 提交于 
      walk_addr_generic() permission checks are a maze of branchy code, which is
performed four times per lookup.  It depends on the type of access, efer.nxe,
cr0.wp, cr4.smep, and in the near future, cr4.smap.

Optimize this away by precalculating all variants and storing them in a
bitmap.  The bitmap is recalculated when rarely-changing variables change
(cr0, cr4) and is indexed by the often-changing variables (page fault error
code, pte access permissions).

The permission check is moved to the end of the loop, otherwise an SMEP
fault could be reported as a false positive, when PDE.U=1 but PTE.U=0.
Noted by Xiao Guangrong.

The result is short, branch-free code.
Reviewed-by: NXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>
      97d64b78
    • A
      KVM: MMU: Push clean gpte write protection out of gpte_access() · 8ea667f2
      由 Avi Kivity 提交于 
      gpte_access() computes the access permissions of a guest pte and also
write-protects clean gptes.  This is wrong when we are servicing a
write fault (since we'll be setting the dirty bit momentarily) but
correct when instantiating a speculative spte, or when servicing a
read fault (since we'll want to trap a following write in order to
set the dirty bit).

It doesn't seem to hurt in practice, but in order to make the code
readable, push the write protection out of gpte_access() and into
a new protect_clean_gpte() which is called explicitly when needed.
Reviewed-by: NXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>
      8ea667f2
  7. 24 7月, 2011 2 次提交
  9. 24 10月, 2010 5 次提交
  11. 01 3月, 2010 5 次提交
  13. 10 9月, 2009 2 次提交
  15. 10 6月, 2009 1 次提交
  17. 24 3月, 2009 1 次提交
  19. 20 7月, 2008 1 次提交
    • A
      KVM: MMU: Fix false flooding when a pte points to page table · 1b7fcd32
      由 Avi Kivity 提交于 
      The KVM MMU tries to detect when a speculative pte update is not actually
used by demand fault, by checking the accessed bit of the shadow pte.  If
the shadow pte has not been accessed, we deem that page table flooded and
remove the shadow page table, allowing further pte updates to proceed
without emulation.

However, if the pte itself points at a page table and only used for write
operations, the accessed bit will never be set since all access will happen
through the emulator.

This is exactly what happens with kscand on old (2.4.x) HIGHMEM kernels.
The kernel points a kmap_atomic() pte at a page table, and then
proceeds with read-modify-write operations to look at the dirty and accessed
bits.  We get a false flood trigger on the kmap ptes, which results in the
mmu spending all its time setting up and tearing down shadows.

Fix by setting the shadow accessed bit on emulated accesses.
Signed-off-by: NAvi Kivity <avi@qumranet.com>
      1b7fcd32
  21. 04 5月, 2008 2 次提交
  23. 27 4月, 2008 1 次提交
  25. 31 1月, 2008 1 次提交
  27. 30 1月, 2008 2 次提交