x86emul: fix vector-length check for AVX512F scalar fused-multiply-add insns

The check needs to happen whenever EVEX.b (SDM nomenclature) is clear,
not just in the memory operand case.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c
index d6c97651e22bfd39f620288602cb025caf7faeed..a3d7e33385d23ab3329f278893b41dfc2260e7c8 100644 (file)
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -8532,11 +8532,9 @@ x86_emulate(
     case X86EMUL_OPC_EVEX_66(0x0f38, 0xbd): /* vfnmadd231s{s,d} xmm/mem,xmm,xmm{k} */
     case X86EMUL_OPC_EVEX_66(0x0f38, 0xbf): /* vfnmsub231s{s,d} xmm/mem,xmm,xmm{k} */
         host_and_vcpu_must_have(avx512f);
-        if ( ea.type == OP_MEM )
-        {
-            generate_exception_if(evex.br, EXC_UD);
+        generate_exception_if(ea.type != OP_REG && evex.br, EXC_UD);
+        if ( !evex.br )
             avx512_vlen_check(true);
-        }
         goto simd_zmm;
 
     case X86EMUL_OPC(0x0f38, 0xc8):     /* sha1nexte xmm/m128,xmm */