KVM: x86 emulator: x86_emulate_insn() return -1 only in case of emulation failure
Currently emulator returns -1 when emulation failed or IO is needed.
Caller tries to guess whether emulation failed by looking at other
variables. Make it easier for caller to recognise error condition by
always returning -1 in case of failure. For this new emulator
internal return value X86EMUL_IO_NEEDED is introduced. It is used to
distinguish between error condition (which returns X86EMUL_UNHANDLEABLE)
and condition that requires IO exit to userspace to continue emulation.
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b976c4c..4cb65d8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3275,7 +3275,7 @@
}
ret = kvm_read_guest(vcpu->kvm, gpa, data, toread);
if (ret < 0) {
- r = X86EMUL_UNHANDLEABLE;
+ r = X86EMUL_IO_NEEDED;
goto out;
}
@@ -3331,7 +3331,7 @@
}
ret = kvm_write_guest(vcpu->kvm, gpa, data, towrite);
if (ret < 0) {
- r = X86EMUL_UNHANDLEABLE;
+ r = X86EMUL_IO_NEEDED;
goto out;
}
@@ -3391,7 +3391,7 @@
vcpu->run->mmio.len = vcpu->mmio_size = bytes;
vcpu->run->mmio.is_write = vcpu->mmio_is_write = 0;
- return X86EMUL_UNHANDLEABLE;
+ return X86EMUL_IO_NEEDED;
}
int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa,
@@ -3863,8 +3863,6 @@
*/
cache_all_regs(vcpu);
- vcpu->mmio_is_write = 0;
-
if (!(emulation_type & EMULTYPE_NO_DECODE)) {
int cs_db, cs_l;
kvm_x86_ops->get_cs_db_l_bits(vcpu, &cs_db, &cs_l);
@@ -3938,24 +3936,26 @@
return EMULATE_DO_MMIO;
}
- if (r) {
+ if (vcpu->mmio_needed) {
+ if (vcpu->mmio_is_write)
+ vcpu->mmio_needed = 0;
+ return EMULATE_DO_MMIO;
+ }
+
+ if (r) { /* emulation failed */
+ /*
+ * if emulation was due to access to shadowed page table
+ * and it failed try to unshadow page and re-entetr the
+ * guest to let CPU execute the instruction.
+ */
if (kvm_mmu_unprotect_page_virt(vcpu, cr2))
- goto done;
- if (!vcpu->mmio_needed) {
- ++vcpu->stat.insn_emulation_fail;
- trace_kvm_emulate_insn_failed(vcpu);
- kvm_report_emulation_failure(vcpu, "mmio");
- return EMULATE_FAIL;
- }
- return EMULATE_DO_MMIO;
+ return EMULATE_DONE;
+
+ trace_kvm_emulate_insn_failed(vcpu);
+ kvm_report_emulation_failure(vcpu, "mmio");
+ return EMULATE_FAIL;
}
- if (vcpu->mmio_is_write) {
- vcpu->mmio_needed = 0;
- return EMULATE_DO_MMIO;
- }
-
-done:
if (vcpu->arch.exception.pending)
vcpu->arch.emulate_ctxt.restart = false;