KVM: APIC: avoid instruction emulation for EOI writes

Instruction emulation for EOI writes can be skipped, since sane
guest simply uses MOV instead of string operations. This is a nice
improvement when guest doesn't support x2apic or hyper-V EOI
support.

a single VM bandwidth is observed with ~8% bandwidth improvement
(7.4Gbps->8Gbps), by saving ~5% cycles from EOI emulation.

Signed-off-by: Kevin Tian <kevin.tian@intel.com>
<Based on earlier work from>:
Signed-off-by: Eddie Dong <eddie.dong@intel.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 2caf290e9895..31f180c21ce9 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -350,6 +350,18 @@ enum vmcs_field {
 #define DEBUG_REG_ACCESS_REG(eq)        (((eq) >> 8) & 0xf) /* 11:8, general purpose reg. */
 
 
+/*
+ * Exit Qualifications for APIC-Access
+ */
+#define APIC_ACCESS_OFFSET              0xfff   /* 11:0, offset within the APIC page */
+#define APIC_ACCESS_TYPE                0xf000  /* 15:12, access type */
+#define TYPE_LINEAR_APIC_INST_READ      (0 << 12)
+#define TYPE_LINEAR_APIC_INST_WRITE     (1 << 12)
+#define TYPE_LINEAR_APIC_INST_FETCH     (2 << 12)
+#define TYPE_LINEAR_APIC_EVENT          (3 << 12)
+#define TYPE_PHYSICAL_APIC_EVENT        (10 << 12)
+#define TYPE_PHYSICAL_APIC_INST         (15 << 12)
+
 /* segment AR */
 #define SEGMENT_AR_L_MASK (1 << 13)