[PATCH v2 5/9] i386: hvf: Make long mode enter and exit clearer

[Roman Bolshakov <r.bolshakov@yadro.com>]

From: Cameron Esfahani <dirty@apple.com>

Intel SDM "9.8.5 Initializing IA-32e Mode" and "9.8.5.4 Switching Out of
IA-32e Mode Operation" define activation and deactivation of long mode
only upon a change of CR0.PG but current code invokes exit_long_mode()
unconditionally until LME is cleared.

Signed-off-by: Cameron Esfahani <dirty@apple.com>
Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
---
 target/i386/hvf/vmx.h | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/target/i386/hvf/vmx.h b/target/i386/hvf/vmx.h
index 1e8b29bf7d..437238f11d 100644
--- a/target/i386/hvf/vmx.h
+++ b/target/i386/hvf/vmx.h
@@ -121,6 +121,7 @@ static inline void macvm_set_cr0(hv_vcpuid_t vcpu, uint64_t cr0)
     uint64_t pdpte[4] = {0, 0, 0, 0};
     uint64_t efer = rvmcs(vcpu, VMCS_GUEST_IA32_EFER);
     uint64_t old_cr0 = rvmcs(vcpu, VMCS_GUEST_CR0);
+    uint64_t changed_cr0 = old_cr0 ^ cr0;
     uint64_t mask = CR0_PG | CR0_CD | CR0_NW | CR0_NE | CR0_ET;
 
     if ((cr0 & CR0_PG) && (rvmcs(vcpu, VMCS_GUEST_CR4) & CR4_PAE) &&
@@ -138,11 +139,12 @@ static inline void macvm_set_cr0(hv_vcpuid_t vcpu, uint64_t cr0)
     wvmcs(vcpu, VMCS_CR0_SHADOW, cr0);
 
     if (efer & MSR_EFER_LME) {
-        if (!(old_cr0 & CR0_PG) && (cr0 & CR0_PG)) {
-            enter_long_mode(vcpu, cr0, efer);
-        }
-        if (/*(old_cr0 & CR0_PG) &&*/ !(cr0 & CR0_PG)) {
-            exit_long_mode(vcpu, cr0, efer);
+        if (changed_cr0 & CR0_PG) {
+            if (cr0 & CR0_PG) {
+                enter_long_mode(vcpu, cr0, efer);
+            } else {
+                exit_long_mode(vcpu, cr0, efer);
+            }
         }
     }
 
-- 
2.26.1