[Xen-devel] [PATCH] libxc: Expose the MPX cpuid flag to guest

[Liang Li <liang.z.li@xxxxxxxxx>]

If hardware support memory protect externsion, expose this feature
to guest by default. Users don't have to use a 'cpuid= ' option in
config file to turn it on.

Signed-off-by: Liang Li <liang.z.li@xxxxxxxxx>
---
 tools/libxc/xc_cpufeature.h | 1 +
 tools/libxc/xc_cpuid_x86.c  | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/tools/libxc/xc_cpufeature.h b/tools/libxc/xc_cpufeature.h
index c3ddc80..cda9305 100644
--- a/tools/libxc/xc_cpufeature.h
+++ b/tools/libxc/xc_cpufeature.h
@@ -137,6 +137,7 @@
 #define X86_FEATURE_ERMS         9 /* Enhanced REP MOVSB/STOSB */
 #define X86_FEATURE_INVPCID     10 /* Invalidate Process Context ID */
 #define X86_FEATURE_RTM         11 /* Restricted Transactional Memory */
+#define X86_FEATURE_MPX         14 /* Memory Protection Extensions */
 #define X86_FEATURE_RDSEED      18 /* RDSEED instruction */
 #define X86_FEATURE_ADX         19 /* ADCX, ADOX instructions */
 #define X86_FEATURE_SMAP        20 /* Supervisor Mode Access Protection */
diff --git a/tools/libxc/xc_cpuid_x86.c b/tools/libxc/xc_cpuid_x86.c
index 8882c01..4c88db4 100644
--- a/tools/libxc/xc_cpuid_x86.c
+++ b/tools/libxc/xc_cpuid_x86.c
@@ -423,6 +423,8 @@ static void xc_cpuid_hvm_policy(xc_interface *xch,
                         bitmaskof(X86_FEATURE_ERMS) |
                         bitmaskof(X86_FEATURE_INVPCID) |
                         bitmaskof(X86_FEATURE_RTM)  |
+                        ((info->xfeature_mask != 0) ?
+                        bitmaskof(X86_FEATURE_MPX) : 0)  |
                         bitmaskof(X86_FEATURE_RDSEED)  |
                         bitmaskof(X86_FEATURE_ADX)  |
                         bitmaskof(X86_FEATURE_SMAP) |
@@ -538,6 +540,7 @@ static void xc_cpuid_pv_policy(xc_interface *xch,
 
     case 0x00000007:
         if ( input[1] == 0 )
+        {
             regs[1] &= (bitmaskof(X86_FEATURE_BMI1) |
                         bitmaskof(X86_FEATURE_HLE)  |
                         bitmaskof(X86_FEATURE_AVX2) |
@@ -547,6 +550,9 @@ static void xc_cpuid_pv_policy(xc_interface *xch,
                         bitmaskof(X86_FEATURE_RDSEED)  |
                         bitmaskof(X86_FEATURE_ADX)  |
                         bitmaskof(X86_FEATURE_FSGSBASE));
+            if ( info->xfeature_mask == 0 )
+                clear_bit(X86_FEATURE_MPX, regs[1]);
+        }
         else
             regs[1] = 0;
         regs[0] = regs[2] = regs[3] = 0;
-- 
1.9.1


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