kvm: x86: vmx: avoid returning bool to distinguish success from error

Return a negative error code instead, and WARN() when we should be covering
the entire 2-bit space of vmcs_field_type's return value.  For increased
robustness, add a BUILD_BUG_ON checking the range of vmcs_field_to_offset.

Suggested-by: Tiejun Chen <tiejun.chen@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 12f6f9a8dd8dfff5846f2fad3a7eda58caca083d..d6e3ddace0743804e01d118087c7db33f8b17cc2 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -720,12 +720,15 @@ static const unsigned short vmcs_field_to_offset_table[] = {
        FIELD(HOST_RSP, host_rsp),
        FIELD(HOST_RIP, host_rip),
 };
-static const int max_vmcs_field = ARRAY_SIZE(vmcs_field_to_offset_table);
 
 static inline short vmcs_field_to_offset(unsigned long field)
 {
-       if (field >= max_vmcs_field || vmcs_field_to_offset_table[field] == 0)
-               return -1;
+       BUILD_BUG_ON(ARRAY_SIZE(vmcs_field_to_offset_table) > SHRT_MAX);
+
+       if (field >= ARRAY_SIZE(vmcs_field_to_offset_table) ||
+           vmcs_field_to_offset_table[field] == 0)
+               return -ENOENT;
+
        return vmcs_field_to_offset_table[field];
 }
 
@@ -6492,58 +6495,60 @@ static inline int vmcs_field_readonly(unsigned long field)
  * some of the bits we return here (e.g., on 32-bit guests, only 32 bits of
  * 64-bit fields are to be returned).
  */
-static inline bool vmcs12_read_any(struct kvm_vcpu *vcpu,
-                                       unsigned long field, u64 *ret)
+static inline int vmcs12_read_any(struct kvm_vcpu *vcpu,
+                                 unsigned long field, u64 *ret)
 {
        short offset = vmcs_field_to_offset(field);
        char *p;
 
        if (offset < 0)
-               return 0;
+               return offset;
 
        p = ((char *)(get_vmcs12(vcpu))) + offset;
 
        switch (vmcs_field_type(field)) {
        case VMCS_FIELD_TYPE_NATURAL_WIDTH:
                *ret = *((natural_width *)p);
-               return 1;
+               return 0;
        case VMCS_FIELD_TYPE_U16:
                *ret = *((u16 *)p);
-               return 1;
+               return 0;
        case VMCS_FIELD_TYPE_U32:
                *ret = *((u32 *)p);
-               return 1;
+               return 0;
        case VMCS_FIELD_TYPE_U64:
                *ret = *((u64 *)p);
-               return 1;
+               return 0;
        default:
-               return 0; /* can never happen. */
+               WARN_ON(1);
+               return -ENOENT;
        }
 }
 
 
-static inline bool vmcs12_write_any(struct kvm_vcpu *vcpu,
-                                   unsigned long field, u64 field_value){
+static inline int vmcs12_write_any(struct kvm_vcpu *vcpu,
+                                  unsigned long field, u64 field_value){
        short offset = vmcs_field_to_offset(field);
        char *p = ((char *) get_vmcs12(vcpu)) + offset;
        if (offset < 0)
-               return false;
+               return offset;
 
        switch (vmcs_field_type(field)) {
        case VMCS_FIELD_TYPE_U16:
                *(u16 *)p = field_value;
-               return true;
+               return 0;
        case VMCS_FIELD_TYPE_U32:
                *(u32 *)p = field_value;
-               return true;
+               return 0;
        case VMCS_FIELD_TYPE_U64:
                *(u64 *)p = field_value;
-               return true;
+               return 0;
        case VMCS_FIELD_TYPE_NATURAL_WIDTH:
                *(natural_width *)p = field_value;
-               return true;
+               return 0;
        default:
-               return false; /* can never happen. */
+               WARN_ON(1);
+               return -ENOENT;
        }
 
 }
@@ -6576,6 +6581,9 @@ static void copy_shadow_to_vmcs12(struct vcpu_vmx *vmx)
                case VMCS_FIELD_TYPE_NATURAL_WIDTH:
                        field_value = vmcs_readl(field);
                        break;
+               default:
+                       WARN_ON(1);
+                       continue;
                }
                vmcs12_write_any(&vmx->vcpu, field, field_value);
        }
@@ -6621,6 +6629,9 @@ static void copy_vmcs12_to_shadow(struct vcpu_vmx *vmx)
                        case VMCS_FIELD_TYPE_NATURAL_WIDTH:
                                vmcs_writel(field, (long)field_value);
                                break;
+                       default:
+                               WARN_ON(1);
+                               break;
                        }
                }
        }
@@ -6659,7 +6670,7 @@ static int handle_vmread(struct kvm_vcpu *vcpu)
        /* Decode instruction info and find the field to read */
        field = kvm_register_readl(vcpu, (((vmx_instruction_info) >> 28) & 0xf));
        /* Read the field, zero-extended to a u64 field_value */
-       if (!vmcs12_read_any(vcpu, field, &field_value)) {
+       if (vmcs12_read_any(vcpu, field, &field_value) < 0) {
                nested_vmx_failValid(vcpu, VMXERR_UNSUPPORTED_VMCS_COMPONENT);
                skip_emulated_instruction(vcpu);
                return 1;
@@ -6729,7 +6740,7 @@ static int handle_vmwrite(struct kvm_vcpu *vcpu)
                return 1;
        }
 
-       if (!vmcs12_write_any(vcpu, field, field_value)) {
+       if (vmcs12_write_any(vcpu, field, field_value) < 0) {
                nested_vmx_failValid(vcpu, VMXERR_UNSUPPORTED_VMCS_COMPONENT);
                skip_emulated_instruction(vcpu);
                return 1;