KVM: x86: Make indirect calls in emulator speculation safe

Replace the indirect calls with CALL_NOSPEC.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Jun Nakajima <jun.nakajima@intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: rga@amazon.de
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Asit Mallick <asit.k.mallick@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Arjan Van De Ven <arjan.van.de.ven@intel.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Link: https://lkml.kernel.org/r/20180125095843.595615683@infradead.org

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index d90cdc77e077354f1407235e6b73f2fda21c430c..453d8c99010822222b8a1d9433d0bdfc6dc50fd9 100644 (file)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -25,6 +25,7 @@
 #include <asm/kvm_emulate.h>
 #include <linux/stringify.h>
 #include <asm/debugreg.h>
+#include <asm/nospec-branch.h>
 
 #include "x86.h"
 #include "tss.h"
@@ -1021,8 +1022,8 @@ static __always_inline u8 test_cc(unsigned int condition, unsigned long flags)
        void (*fop)(void) = (void *)em_setcc + 4 * (condition & 0xf);
 
        flags = (flags & EFLAGS_MASK) | X86_EFLAGS_IF;
-       asm("push %[flags]; popf; call *%[fastop]"
-           : "=a"(rc) : [fastop]"r"(fop), [flags]"r"(flags));
+       asm("push %[flags]; popf; " CALL_NOSPEC
+           : "=a"(rc) : [thunk_target]"r"(fop), [flags]"r"(flags));
        return rc;
 }
 
@@ -5305,9 +5306,9 @@ static int fastop(struct x86_emulate_ctxt *ctxt, void (*fop)(struct fastop *))
        if (!(ctxt->d & ByteOp))
                fop += __ffs(ctxt->dst.bytes) * FASTOP_SIZE;
 
-       asm("push %[flags]; popf; call *%[fastop]; pushf; pop %[flags]\n"
+       asm("push %[flags]; popf; " CALL_NOSPEC " ; pushf; pop %[flags]\n"
            : "+a"(ctxt->dst.val), "+d"(ctxt->src.val), [flags]"+D"(flags),
-             [fastop]"+S"(fop), ASM_CALL_CONSTRAINT
+             [thunk_target]"+S"(fop), ASM_CALL_CONSTRAINT
            : "c"(ctxt->src2.val));
 
        ctxt->eflags = (ctxt->eflags & ~EFLAGS_MASK) | (flags & EFLAGS_MASK);