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

[patchbot@xxxxxxx]

commit 0d4d9e8f55602415475e04a5dc8b4ad27845a7f9
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Dec 18 15:19:47 2018 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Dec 18 15:19:47 2018 +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>
---
 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 7f694fea17..d6c97651e2 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -6079,9 +6079,11 @@ 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);
@@ -6984,6 +6986,9 @@ 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;
@@ -8816,6 +8821,11 @@ 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#staging

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