[Xen-changelog] [xen stable-4.11] x86emul: work around SandyBridge errata

[patchbot@xxxxxxx]

commit 2cd833de4dae3898849a0eea5298644e2890e018
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri Feb 1 11:33:09 2019 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Feb 1 11:33:09 2019 +0100

    x86emul: work around SandyBridge errata
    
    There are a number of exception condition related errata on SandyBridge
    CPUs, some of which are unexpected #UD (others, of no interest here, are
    lack of mandated exceptions, or exceptions of unexpected type). Annotate
    the one workaround we already have, and add two more.
    
    Due to the exception recovery we have in place for stub invocations
    these aren't security issues.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: 0d4d9e8f55602415475e04a5dc8b4ad27845a7f9
    master date: 2018-12-18 15:19:47 +0100
---
 xen/arch/x86/x86_emulate/x86_emulate.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c 
b/xen/arch/x86/x86_emulate/x86_emulate.c
index e7640e58cb..b1f3b568ab 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -5766,9 +5766,11 @@ x86_emulate(
         else
         {
             generate_exception_if(vex.reg != 0xf, EXC_UD);
-            vex.l = 0;
             host_and_vcpu_must_have(avx);
             get_fpu(X86EMUL_FPU_ymm);
+
+            /* Work around erratum BT230. */
+            vex.l = 0;
         }
 
         opc = init_prefixes(stub);
@@ -6452,6 +6454,9 @@ x86_emulate(
             get_fpu(X86EMUL_FPU_mmx);
         }
 
+        /* Work around erratum BT36. */
+        vex.w = 0;
+
         opc = init_prefixes(stub);
         opc[0] = b;
         insn_bytes = PFX_BYTES + 1;
@@ -8060,6 +8065,11 @@ x86_emulate(
         generate_exception_if(vex.l || vex.reg != 0xf, EXC_UD);
         host_and_vcpu_must_have(avx);
         get_fpu(X86EMUL_FPU_ymm);
+
+        /* Work around erratum BT41. */
+        if ( !mode_64bit() )
+            vex.w = 0;
+
         opc = init_prefixes(stub);
         goto pextr;
 
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.11

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