diff options
| author | Xiao Guangrong | 2013-07-18 12:52:37 +0800 |
|---|---|---|
| committer | Paolo Bonzini | 2013-07-18 12:26:57 +0200 |
| commit | 1c118b8226922d225a7df4127926ed2a2d73baaf (patch) | |
| tree | ca449c37fe18b62177960281b16f201df813b5a7 | |
| parent | ad81f0545ef01ea651886dddac4bef6cec930092 (diff) | |
KVM: MMU: avoid fast page fault fixing mmio page fault
Currently, fast page fault incorrectly tries to fix mmio page fault when
the generation number is invalid (spte.gen != kvm.gen). It then returns
to guest to retry the fault since it sees the last spte is nonpresent.
This causes an infinite loop.
Since fast page fault only works for direct mmu, the issue exists when
1) tdp is enabled. It is only triggered only on AMD host since on Intel host
the mmio page fault is recognized as ept-misconfig whose handler call
fault-page path with error_code = 0
2) guest paging is disabled. Under this case, the issue is hardly discovered
since paging disable is short-lived and the sptes will be invalid after
memslot changed for 150 times
Fix it by filtering out MMIO page faults in page_fault_can_be_fast.
Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Tested-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
| -rw-r--r-- | arch/x86/kvm/mmu.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 0d094da49541..9e9285ae9b94 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -2811,6 +2811,13 @@ exit: static bool page_fault_can_be_fast(struct kvm_vcpu *vcpu, u32 error_code) { /* + * Do not fix the mmio spte with invalid generation number which + * need to be updated by slow page fault path. + */ + if (unlikely(error_code & PFERR_RSVD_MASK)) + return false; + + /* * #PF can be fast only if the shadow page table is present and it * is caused by write-protect, that means we just need change the * W bit of the spte which can be done out of mmu-lock. |