[Xen-devel] [PATCH v3 3/3] Nested VMX: Fix IA32_VMX_CR4_FIXED1 msr emulation

[Yang Zhang <yang.z.zhang@xxxxxxxxx>]

From: Yang Zhang <yang.z.zhang@xxxxxxxxx>

Currently, it use hardcode value for IA32_VMX_CR4_FIXED1. This is wrong.
We should check guest's cpuid to know which bits are writeable in CR4 by guest
and allow the guest to set the corresponding bit only when guest has the 
feature.

Signed-off-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
---
 xen/arch/x86/hvm/vmx/vvmx.c      |   49 ++++++++++++++++++++++++++++++++++++-
 xen/include/asm-x86/cpufeature.h |    1 +
 xen/include/asm-x86/processor.h  |    1 +
 3 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vvmx.c b/xen/arch/x86/hvm/vmx/vvmx.c
index 48cfbc6..f9c7832 100644
--- a/xen/arch/x86/hvm/vmx/vvmx.c
+++ b/xen/arch/x86/hvm/vmx/vvmx.c
@@ -1947,8 +1947,53 @@ int nvmx_msr_read_intercept(unsigned int msr, u64 
*msr_content)
         data = X86_CR4_VMXE;
         break;
     case MSR_IA32_VMX_CR4_FIXED1:
-        /* allow 0-settings except SMXE */
-        data = 0x267ff & ~X86_CR4_SMXE;
+        if ( edx & cpufeat_mask(X86_FEATURE_VME) )
+            data |= X86_CR4_VME | X86_CR4_PVI;
+        if ( edx & cpufeat_mask(X86_FEATURE_TSC) )
+            data |= X86_CR4_TSD;
+        if ( edx & cpufeat_mask(X86_FEATURE_DE) )
+            data |= X86_CR4_DE;
+        if ( edx & cpufeat_mask(X86_FEATURE_PSE) )
+            data |= X86_CR4_PSE;
+        if ( edx & cpufeat_mask(X86_FEATURE_PAE) )
+            data |= X86_CR4_PAE;
+        if ( edx & cpufeat_mask(X86_FEATURE_MCE) )
+            data |= X86_CR4_MCE;
+        if ( edx & cpufeat_mask(X86_FEATURE_PGE) )
+            data |= X86_CR4_PGE;
+        if ( edx & cpufeat_mask(X86_FEATURE_FXSR) )
+            data |= X86_CR4_OSFXSR;
+        if ( edx & cpufeat_mask(X86_FEATURE_XMM) )
+            data |= X86_CR4_OSXMMEXCPT;
+        if ( ecx & cpufeat_mask(X86_FEATURE_VMXE) )
+            data |= X86_CR4_VMXE;
+        if ( ecx & cpufeat_mask(X86_FEATURE_SMXE) )
+            data |= X86_CR4_SMXE;
+        if ( ecx & cpufeat_mask(X86_FEATURE_PCID) )
+            data |= X86_CR4_PCIDE;
+        if ( ecx & cpufeat_mask(X86_FEATURE_XSAVE) )
+            data |= X86_CR4_OSXSAVE;
+
+        hvm_cpuid(0x0, &eax, &ebx, &ecx, &edx);
+        if ( eax >= 0x7 )
+        {
+            ecx = 0;
+            hvm_cpuid(0x7, &ecx, &ebx, &ecx, &edx);
+            if ( ebx & cpufeat_mask(X86_FEATURE_FSGSBASE) )
+                data |= X86_CR4_FSGSBASE;
+            if ( ebx & cpufeat_mask(X86_FEATURE_SMEP) )
+                data |= X86_CR4_SMEP;
+            if ( ebx & cpufeat_mask(X86_FEATURE_SMAP) )
+                data |= X86_CR4_SMAP;
+
+            if ( eax >= 0xa )
+            {
+                hvm_cpuid(0xa, &eax, &ebx, &ecx, &edx);
+                /* Check whether guest has the perf monitor feature. */
+                if ( (eax & 0xff) && (eax & 0xff00) )
+                    data |= X86_CR4_PCE;
+            }
+        }
         break;
     case MSR_IA32_VMX_MISC:
         /* Do not support CR3-target feature now */
diff --git a/xen/include/asm-x86/cpufeature.h b/xen/include/asm-x86/cpufeature.h
index 065c265..73d5cb6 100644
--- a/xen/include/asm-x86/cpufeature.h
+++ b/xen/include/asm-x86/cpufeature.h
@@ -148,6 +148,7 @@
 #define X86_FEATURE_INVPCID    (7*32+10) /* Invalidate Process Context ID */
 #define X86_FEATURE_RTM        (7*32+11) /* Restricted Transactional Memory */
 #define X86_FEATURE_NO_FPU_SEL         (7*32+13) /* FPU CS/DS stored as zero */
+#define X86_FEATURE_SMAP       (7*32+ 20) /* Supervisor Mode Access Prevention 
*/
 
 #define cpu_has(c, bit)                test_bit(bit, (c)->x86_capability)
 #define boot_cpu_has(bit)      test_bit(bit, boot_cpu_data.x86_capability)
diff --git a/xen/include/asm-x86/processor.h b/xen/include/asm-x86/processor.h
index 5cdacc7..893afa3 100644
--- a/xen/include/asm-x86/processor.h
+++ b/xen/include/asm-x86/processor.h
@@ -87,6 +87,7 @@
 #define X86_CR4_PCIDE          0x20000 /* enable PCID */
 #define X86_CR4_OSXSAVE        0x40000 /* enable XSAVE/XRSTOR */
 #define X86_CR4_SMEP           0x100000/* enable SMEP */
+#define X86_CR4_SMAP           0x200000/* enable SMAP */
 
 /*
  * Trap/fault mnemonics.
-- 
1.7.1


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