KVM: vmx: detect mismatched size in VMCS read/write

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
	I am sending this as RFC because the error messages it produces are
	very ugly.  Because of inlining, the original line is lost.  The
	alternative is to change vmcs_read/write/checkXX into macros, but
	then you need to have a single huge BUILD_BUG_ON or BUILD_BUG_ON_MSG
	because multiple BUILD_BUG_ON* with the same __LINE__ are not
	supported well.

arch/x86/kvm/vmx.c

@@ -1447,7 +1447,51 @@ static inline void ept_sync_context(u64 eptp)
 	}
 }
 
-static __always_inline unsigned long vmcs_readl(unsigned long field)
+static __always_inline void vmcs_check16(unsigned long field)
+{
+        BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6001) == 0x2000,
+			 "16-bit accessor invalid for 64-bit field");
+        BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6001) == 0x2001,
+			 "16-bit accessor invalid for 64-bit high field");
+        BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0x4000,
+			 "16-bit accessor invalid for 32-bit high field");
+        BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0x6000,
+			 "16-bit accessor invalid for natural width field");
+}
+
+static __always_inline void vmcs_check32(unsigned long field)
+{
+        BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0,
+			 "32-bit accessor invalid for 16-bit field");
+        BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0x6000,
+			 "32-bit accessor invalid for natural width field");
+}
+
+static __always_inline void vmcs_check64(unsigned long field)
+{
+        BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0,
+			 "64-bit accessor invalid for 16-bit field");
+        BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6001) == 0x2001,
+			 "64-bit accessor invalid for 64-bit high field");
+        BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0x4000,
+			 "64-bit accessor invalid for 32-bit field");
+        BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0x6000,
+			 "64-bit accessor invalid for natural width field");
+}
+
+static __always_inline void vmcs_checkl(unsigned long field)
+{
+        BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0,
+			 "Natural width accessor invalid for 16-bit field");
+        BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6001) == 0x2000,
+			 "Natural width accessor invalid for 64-bit field");
+        BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6001) == 0x2001,
+			 "Natural width accessor invalid for 64-bit high field");
+        BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0x4000,
+			 "Natural width accessor invalid for 32-bit field");
+}
+
+static __always_inline unsigned long __vmcs_readl(unsigned long field)
 {
 	unsigned long value;
 
@@ -1458,23 +1502,32 @@ static __always_inline unsigned long vmcs_readl(unsigned long field)
 
 static __always_inline u16 vmcs_read16(unsigned long field)
 {
-	return vmcs_readl(field);
+	vmcs_check16(field);
+	return __vmcs_readl(field);
 }
 
 static __always_inline u32 vmcs_read32(unsigned long field)
 {
-	return vmcs_readl(field);
+	vmcs_check32(field);
+	return __vmcs_readl(field);
 }
 
 static __always_inline u64 vmcs_read64(unsigned long field)
 {
+	vmcs_check64(field);
 #ifdef CONFIG_X86_64
-	return vmcs_readl(field);
+	return __vmcs_readl(field);
 #else
-	return vmcs_readl(field) | ((u64)vmcs_readl(field+1) << 32);
+	return __vmcs_readl(field) | ((u64)__vmcs_readl(field+1) << 32);
 #endif
 }
 
+static __always_inline unsigned long vmcs_readl(unsigned long field)
+{
+	vmcs_checkl(field);
+	return __vmcs_readl(field);
+}
+
 static noinline void vmwrite_error(unsigned long field, unsigned long value)
 {
 	printk(KERN_ERR "vmwrite error: reg %lx value %lx (err %d)\n",
@@ -1482,7 +1535,7 @@ static noinline void vmwrite_error(unsigned long field, unsigned long value)
 	dump_stack();
 }
 
-static void vmcs_writel(unsigned long field, unsigned long value)
+static __always_inline void __vmcs_writel(unsigned long field, unsigned long value)
 {
 	u8 error;
 
@@ -1492,33 +1545,46 @@ static void vmcs_writel(unsigned long field, unsigned long value)
 		vmwrite_error(field, value);
 }
 
-static void vmcs_write16(unsigned long field, u16 value)
+static __always_inline void vmcs_write16(unsigned long field, u16 value)
 {
-	vmcs_writel(field, value);
+	vmcs_check16(field);
+	__vmcs_writel(field, value);
 }
 
-static void vmcs_write32(unsigned long field, u32 value)
+static __always_inline void vmcs_write32(unsigned long field, u32 value)
 {
-	vmcs_writel(field, value);
+	vmcs_check32(field);
+	__vmcs_writel(field, value);
 }
 
-static void vmcs_write64(unsigned long field, u64 value)
+static __always_inline void vmcs_write64(unsigned long field, u64 value)
 {
-	vmcs_writel(field, value);
+	vmcs_check64(field);
+	__vmcs_writel(field, value);
 #ifndef CONFIG_X86_64
 	asm volatile ("");
-	vmcs_writel(field+1, value >> 32);
+	__vmcs_writel(field+1, value >> 32);
 #endif
 }
 
-static void vmcs_clear_bits(unsigned long field, u32 mask)
+static __always_inline void vmcs_writel(unsigned long field, unsigned long value)
+{
+	vmcs_checkl(field);
+	__vmcs_writel(field, value);
+}
+
+static __always_inline void vmcs_clear_bits(unsigned long field, u32 mask)
 {
-	vmcs_writel(field, vmcs_readl(field) & ~mask);
+        BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0x2000,
+			 "vmcs_clear_bits does not support 64-bit fields");
+	__vmcs_writel(field, __vmcs_readl(field) & ~mask);
 }
 
-static void vmcs_set_bits(unsigned long field, u32 mask)
+static __always_inline void vmcs_set_bits(unsigned long field, u32 mask)
 {
-	vmcs_writel(field, vmcs_readl(field) | mask);
+        BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0x2000,
+			 "vmcs_set_bits does not support 64-bit fields");
+	__vmcs_writel(field, __vmcs_readl(field) | mask);
 }
 
 static inline void vm_entry_controls_init(struct vcpu_vmx *vmx, u32 val)