diff options
| author | Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> | 2013-01-13 23:49:07 +0800 |
|---|---|---|
| committer | Marcelo Tosatti <mtosatti@redhat.com> | 2013-01-21 22:58:33 -0200 |
| commit | 93c05d3ef25275829d421a255271595ac219a518 (patch) | |
| tree | b987097751977ca63bd9a9ef53956cd0d14127c3 /arch/x86/kvm/x86.c | |
| parent | 95b3cf69bdf8b27a02d878e24ca353cebb4e009e (diff) | |
KVM: x86: improve reexecute_instruction
The current reexecute_instruction can not well detect the failed instruction
emulation. It allows guest to retry all the instructions except it accesses
on error pfn
For example, some cases are nested-write-protect - if the page we want to
write is used as PDE but it chains to itself. Under this case, we should
stop the emulation and report the case to userspace
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Diffstat (limited to 'arch/x86/kvm/x86.c')
| -rw-r--r-- | arch/x86/kvm/x86.c | 22 |
1 files changed, 18 insertions, 4 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 6f9cab071eca..e00dd0515a84 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4751,7 +4751,8 @@ static int handle_emulation_failure(struct kvm_vcpu *vcpu) return r; } -static bool reexecute_instruction(struct kvm_vcpu *vcpu, gva_t cr2) +static bool reexecute_instruction(struct kvm_vcpu *vcpu, gva_t cr2, + bool write_fault_to_shadow_pgtable) { gpa_t gpa = cr2; pfn_t pfn; @@ -4808,7 +4809,13 @@ static bool reexecute_instruction(struct kvm_vcpu *vcpu, gva_t cr2) * guest to let CPU execute the instruction. */ kvm_mmu_unprotect_page(vcpu->kvm, gpa_to_gfn(gpa)); - return true; + + /* + * If the access faults on its page table, it can not + * be fixed by unprotecting shadow page and it should + * be reported to userspace. + */ + return !write_fault_to_shadow_pgtable; } static bool retry_instruction(struct x86_emulate_ctxt *ctxt, @@ -4867,7 +4874,13 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, int r; struct x86_emulate_ctxt *ctxt = &vcpu->arch.emulate_ctxt; bool writeback = true; + bool write_fault_to_spt = vcpu->arch.write_fault_to_shadow_pgtable; + /* + * Clear write_fault_to_shadow_pgtable here to ensure it is + * never reused. + */ + vcpu->arch.write_fault_to_shadow_pgtable = false; kvm_clear_exception_queue(vcpu); if (!(emulation_type & EMULTYPE_NO_DECODE)) { @@ -4886,7 +4899,8 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, if (r != EMULATION_OK) { if (emulation_type & EMULTYPE_TRAP_UD) return EMULATE_FAIL; - if (reexecute_instruction(vcpu, cr2)) + if (reexecute_instruction(vcpu, cr2, + write_fault_to_spt)) return EMULATE_DONE; if (emulation_type & EMULTYPE_SKIP) return EMULATE_FAIL; @@ -4916,7 +4930,7 @@ restart: return EMULATE_DONE; if (r == EMULATION_FAILED) { - if (reexecute_instruction(vcpu, cr2)) + if (reexecute_instruction(vcpu, cr2, write_fault_to_spt)) return EMULATE_DONE; return handle_emulation_failure(vcpu); |