[Xen-devel] [PATCH 2/4] x86/vmx: improve __vmread_safe()

[Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>]

The original function doesn't distinguish between Valid and Invalid
VMfails.  Improved function returns error code depending on the outcome:

        VMsucceed: 0
      VMfailValid: VM Instruction Error Number
    VMfailInvalid: VMX_INSN_FAIL_INVALID (~0UL)

Existing users of __vmread_safe() are updated.

Signed-off-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
---
 xen/arch/x86/hvm/vmx/vmcs.c       |  2 +-
 xen/arch/x86/hvm/vmx/vvmx.c       |  2 +-
 xen/include/asm-x86/hvm/vmx/vmx.h | 41 +++++++++++++++++----------------------
 3 files changed, 20 insertions(+), 25 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index 59ef199..641e2ef 100644
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -1711,7 +1711,7 @@ static inline unsigned long vmr(unsigned long field)
 {
     unsigned long val;
 
-    return __vmread_safe(field, &val) ? val : 0;
+    return __vmread_safe(field, &val) ? 0 : val;
 }
 
 #define vmr16(fld) ({             \
diff --git a/xen/arch/x86/hvm/vmx/vvmx.c b/xen/arch/x86/hvm/vmx/vvmx.c
index 105a3c0..e0cf0fb 100644
--- a/xen/arch/x86/hvm/vmx/vvmx.c
+++ b/xen/arch/x86/hvm/vmx/vvmx.c
@@ -932,7 +932,7 @@ static inline void shadow_to_vvmcs(const struct vcpu *v, 
unsigned int field)
 {
     unsigned long value;
 
-    if ( __vmread_safe(field, &value) )
+    if ( __vmread_safe(field, &value) == 0 )
         set_vvmcs(v, field, value);
 }
 
diff --git a/xen/include/asm-x86/hvm/vmx/vmx.h 
b/xen/include/asm-x86/hvm/vmx/vmx.h
index b0f3f3c..8d871cf 100644
--- a/xen/include/asm-x86/hvm/vmx/vmx.h
+++ b/xen/include/asm-x86/hvm/vmx/vmx.h
@@ -401,32 +401,27 @@ static always_inline void __vmwrite(unsigned long field, 
unsigned long value)
         );
 }
 
-static inline bool_t __vmread_safe(unsigned long field, unsigned long *value)
+static inline unsigned long __vmread_safe(unsigned long field,
+                                          unsigned long *value)
 {
-    bool_t okay;
+    unsigned long ret = 0;
+    bool fail_invalid, fail_valid;
 
-    asm volatile (
-#ifdef HAVE_GAS_VMX
-                   "vmread %2, %1\n\t"
-#else
-                   VMREAD_OPCODE MODRM_EAX_ECX
-#endif
-                   /* CF==1 or ZF==1 --> rc = 0 */
-#ifdef __GCC_ASM_FLAG_OUTPUTS__
-                   : "=@ccnbe" (okay),
-#else
-                   "setnbe %0"
-                   : "=qm" (okay),
-#endif
-#ifdef HAVE_GAS_VMX
-                     "=rm" (*value)
-                   : "r" (field));
-#else
-                     "=c" (*value)
-                   : "a" (field));
-#endif
+    asm volatile ( GAS_VMX_OP("vmread %[field], %[value]\n",
+                              VMREAD_OPCODE MODRM_EAX_ECX)
+                   ASM_FLAG_OUT(, "setb %[fail_invalid]\n")
+                   ASM_FLAG_OUT(, "sete %[fail_valid]\n")
+                   : ASM_FLAG_OUT("=@ccb", [fail_invalid] "=rm") 
(fail_invalid),
+                     ASM_FLAG_OUT("=@cce", [fail_valid] "=rm") (fail_valid),
+                     [value] GAS_VMX_OP("=rm", "=c") (*value)
+                   : [field] GAS_VMX_OP("r", "a") (field));
+
+    if ( fail_invalid )
+        ret = VMX_INSN_FAIL_INVALID;
+    else if ( fail_valid )
+        __vmread(VM_INSTRUCTION_ERROR, &ret);
 
-    return okay;
+    return ret;
 }
 
 static always_inline unsigned long __vmwrite_safe(unsigned long field,
-- 
2.7.4


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