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  1. 14 1月, 2013 4 次提交
  3. 11 1月, 2013 2 次提交
    • X
      KVM: MMU: fix infinite fault access retry · 7751babd
      由 Xiao Guangrong 提交于 
      We have two issues in current code:
- if target gfn is used as its page table, guest will refault then kvm will use
  small page size to map it. We need two #PF to fix its shadow page table

- sometimes, say a exception is triggered during vm-exit caused by #PF
  (see handle_exception() in vmx.c), we remove all the shadow pages shadowed
  by the target gfn before go into page fault path, it will cause infinite
  loop:
  delete shadow pages shadowed by the gfn -> try to use large page size to map
  the gfn -> retry the access ->...

To fix these, we can adjust page size early if the target gfn is used as page
table
Signed-off-by: NXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>
      7751babd
    • X
      KVM: MMU: fix Dirty bit missed if CR0.WP = 0 · c2288505
      由 Xiao Guangrong 提交于 
      If the write-fault access is from supervisor and CR0.WP is not set on the
vcpu, kvm will fix it by adjusting pte access - it sets the W bit on pte
and clears U bit. This is the chance that kvm can change pte access from
readonly to writable

Unfortunately, the pte access is the access of 'direct' shadow page table,
means direct sp.role.access = pte_access, then we will create a writable
spte entry on the readonly shadow page table. It will cause Dirty bit is
not tracked when two guest ptes point to the same large page. Note, it
does not have other impact except Dirty bit since cr0.wp is encoded into
sp.role

It can be fixed by adjusting pte access before establishing shadow page
table. Also, after that, no mmu specified code exists in the common function
and drop two parameters in set_spte
Signed-off-by: NXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>
      c2288505
  5. 06 12月, 2012 1 次提交
    • X
      KVM: MMU: optimize for set_spte · c2193463
      由 Xiao Guangrong 提交于 
      There are two cases we need to adjust page size in set_spte:
1): the one is other vcpu creates new sp in the window between mapping_level()
    and acquiring mmu-lock.
2): the another case is the new sp is created by itself (page-fault path) when
    guest uses the target gfn as its page table.

In current code, set_spte drop the spte and emulate the access for these case,
it works not good:
- for the case 1, it may destroy the mapping established by other vcpu, and
  do expensive instruction emulation.
- for the case 2, it may emulate the access even if the guest is accessing
  the page which not used as page table. There is a example, 0~2M is used as
  huge page in guest, in this huge page, only page 3 used as page table, then
  guest read/writes on other pages can cause instruction emulation.

Both of these cases can be fixed by allowing guest to retry the access, it
will refault, then we can establish the mapping by using small page
Signed-off-by: NXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Acked-by: NMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>
      c2193463
  7. 30 10月, 2012 1 次提交
  9. 23 10月, 2012 2 次提交
  11. 17 10月, 2012 2 次提交
  13. 20 9月, 2012 4 次提交
  15. 10 9月, 2012 1 次提交
  17. 22 8月, 2012 3 次提交
  19. 06 8月, 2012 5 次提交
  21. 26 7月, 2012 1 次提交
  23. 20 7月, 2012 3 次提交
  25. 19 7月, 2012 8 次提交
  27. 11 7月, 2012 3 次提交