[Xen-devel] [PATCH v4 3/4] Nested VMX: fix IA32_VMX_CR4_FIXED1 msr emulation

["Jan Beulich" <JBeulich@xxxxxxxx>]

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>

Cleanup.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/hvm/vmx/vvmx.c
+++ b/xen/arch/x86/hvm/vmx/vvmx.c
@@ -1813,7 +1813,7 @@ int nvmx_handle_invvpid(struct cpu_user_
 int nvmx_msr_read_intercept(unsigned int msr, u64 *msr_content)
 {
     struct vcpu *v = current;
-    unsigned int ecx, dummy;
+    unsigned int eax, ebx, ecx, edx, dummy;
     u64 data = 0, host_data = 0;
     int r = 1;
 
@@ -1821,7 +1821,7 @@ int nvmx_msr_read_intercept(unsigned int
         return 0;
 
     /* VMX capablity MSRs are available only when guest supports VMX. */
-    hvm_cpuid(0x1, &dummy, &dummy, &ecx, &dummy);
+    hvm_cpuid(0x1, &dummy, &dummy, &ecx, &edx);
     if ( !(ecx & cpufeat_mask(X86_FEATURE_VMXE)) )
         return 0;
 
@@ -1945,8 +1945,55 @@ int nvmx_msr_read_intercept(unsigned int
         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, &dummy, &dummy, &dummy);
+        switch ( eax )
+        {
+        default:
+            hvm_cpuid(0xa, &eax, &dummy, &dummy, &dummy);
+            /* Check whether guest has the perf monitor feature. */
+            if ( (eax & 0xff) && (eax & 0xff00) )
+                data |= X86_CR4_PCE;
+            /* fall through */
+        case 0x7 ... 0x9:
+            ecx = 0;
+            hvm_cpuid(0x7, &dummy, &ebx, &ecx, &dummy);
+            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;
+            /* fall through */
+        case 0x0 ... 0x6:
+            break;
+        }
         break;
     case MSR_IA32_VMX_MISC:
         /* Do not support CR3-target feature now */
--- 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)
--- 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.

Attachment: nVMX-CR4_FIXED1-emulation.patch
Description: Text document

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