x86/kvm: Update spectre-v1 mitigation

[pandora-kernel.git] / arch / x86 / kvm / vmx.c

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 00ad497..24227a8 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -29,6 +29,7 @@
 #include <linux/ftrace_event.h>
 #include <linux/slab.h>
 #include <linux/tboot.h>
+#include <linux/nospec.h>
 #include "kvm_cache_regs.h"
 #include "x86.h"
 
@@ -570,23 +571,21 @@ static 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)
-               return -1;
+       const size_t size = ARRAY_SIZE(vmcs_field_to_offset_table);
+       unsigned short offset;
 
-       /*
-        * FIXME: Mitigation for CVE-2017-5753.  To be replaced with a
-        * generic mechanism.
-        */
-       asm("lfence");
-
-       if (vmcs_field_to_offset_table[field] == 0)
+       BUILD_BUG_ON(size > SHRT_MAX);
+       if (field >= size)
                return -1;
 
-       return vmcs_field_to_offset_table[field];
+       field = array_index_nospec(field, size);
+       offset = vmcs_field_to_offset_table[field];
+       if (offset == 0)
+               return -1;
+       return offset;
 }
 
 static inline struct vmcs12 *get_vmcs12(struct kvm_vcpu *vcpu)