[RFC PATCH 70/73] x86/pvm: Don't use SWAPGS for gsbase read/write

[Lai Jiangshan]

From: Hou Wenlong <houwenlong.hwl@xxxxxxxxxxxx>

On PVM guest, SWAPGS doesn't work. So let __rdgsbase_inactive() and
__wrgsbase_inactive() to use rdmsrl()/wrmsrl() on PVM guest.

Signed-off-by: Hou Wenlong <houwenlong.hwl@xxxxxxxxxxxx>
Signed-off-by: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx>
---
 arch/x86/kernel/process_64.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 33b268747bb7..9a56bcef515e 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -157,7 +157,7 @@ enum which_selector {
  * traced or probed than any access to a per CPU variable happens with
  * the wrong GS.
  *
- * It is not used on Xen paravirt. When paravirt support is needed, it
+ * It is not used on Xen/PVM paravirt. When paravirt support is needed, it
  * needs to be renamed with native_ prefix.
  */
 static noinstr unsigned long __rdgsbase_inactive(void)
@@ -166,7 +166,8 @@ static noinstr unsigned long __rdgsbase_inactive(void)
 
 	lockdep_assert_irqs_disabled();
 
-	if (!cpu_feature_enabled(X86_FEATURE_XENPV)) {
+	if (!cpu_feature_enabled(X86_FEATURE_XENPV) &&
+	    !cpu_feature_enabled(X86_FEATURE_KVM_PVM_GUEST)) {
 		native_swapgs();
 		gsbase = rdgsbase();
 		native_swapgs();
@@ -184,14 +185,15 @@ static noinstr unsigned long __rdgsbase_inactive(void)
  * traced or probed than any access to a per CPU variable happens with
  * the wrong GS.
  *
- * It is not used on Xen paravirt. When paravirt support is needed, it
+ * It is not used on Xen/PVM paravirt. When paravirt support is needed, it
  * needs to be renamed with native_ prefix.
  */
 static noinstr void __wrgsbase_inactive(unsigned long gsbase)
 {
 	lockdep_assert_irqs_disabled();
 
-	if (!cpu_feature_enabled(X86_FEATURE_XENPV)) {
+	if (!cpu_feature_enabled(X86_FEATURE_XENPV) &&
+	    !cpu_feature_enabled(X86_FEATURE_KVM_PVM_GUEST)) {
 		native_swapgs();
 		wrgsbase(gsbase);
 		native_swapgs();
-- 
2.19.1.6.gb485710b