[Xen-changelog] [xen master] x86emul: adjust_bnd() should check XCR0

[patchbot@xxxxxxx]

commit c44dc590f89b02e89b464c6eb14bab07af7baeb1
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Mar 22 10:36:55 2018 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Mar 22 10:36:55 2018 +0100

    x86emul: adjust_bnd() should check XCR0
    
    Experimentally MPX instructions have been confirmed to behave as NOPs
    unless both related XCR0 bits are set to 1. By implication branches
    then also don't clear BNDn.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/x86_emulate/x86_emulate.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c 
b/xen/arch/x86/x86_emulate/x86_emulate.c
index bad5af4254..c4f34ca95c 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -2154,12 +2154,16 @@ static bool umip_active(struct x86_emulate_ctxt *ctxt,
 static void adjust_bnd(struct x86_emulate_ctxt *ctxt,
                        const struct x86_emulate_ops *ops, enum vex_pfx pfx)
 {
-    uint64_t bndcfg;
+    uint64_t xcr0, bndcfg;
     int rc;
 
     if ( pfx == vex_f2 || !cpu_has_mpx || !vcpu_has_mpx() )
         return;
 
+    if ( !ops->read_xcr || ops->read_xcr(0, &xcr0, ctxt) != X86EMUL_OKAY ||
+         !(xcr0 & X86_XCR0_BNDREGS) || !(xcr0 & X86_XCR0_BNDCSR) )
+        return;
+
     if ( !mode_ring0() )
         bndcfg = read_bndcfgu();
     else if ( !ops->read_msr ||
--
generated by git-patchbot for /home/xen/git/xen.git#master

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