KVM: x86 emulator: check io permissions only once for string pio
Do not recheck io permission on every iteration.
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index 0f901c1..8762411 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -224,6 +224,7 @@
int interruptibility;
bool restart; /* restart string instruction after writeback */
+ bool perm_ok; /* do not check permissions if true */
int exception; /* exception that happens during emulation or -1 */
u32 error_code; /* error code for exception */
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 4d49514..760e2b0 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1621,9 +1621,15 @@
struct x86_emulate_ops *ops,
u16 port, u16 len)
{
+ if (ctxt->perm_ok)
+ return true;
+
if (emulator_bad_iopl(ctxt, ops))
if (!emulator_io_port_access_allowed(ctxt, ops, port, len))
return false;
+
+ ctxt->perm_ok = true;
+
return true;
}
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3cbe803..35c0f4e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3997,6 +3997,7 @@
memcpy(c->regs, vcpu->arch.regs, sizeof c->regs);
vcpu->arch.emulate_ctxt.interruptibility = 0;
vcpu->arch.emulate_ctxt.exception = -1;
+ vcpu->arch.emulate_ctxt.perm_ok = false;
r = x86_decode_insn(&vcpu->arch.emulate_ctxt);
trace_kvm_emulate_insn_start(vcpu);