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[Xen-devel] [PATCH] x86emul: correct VEX.W handling for non-64-bit VPINSRD

Going though the XED commits from the last couple of months made me
notice that VPINSRD, other than VPEXTRD, does not clear VEX.W for non-
64-bit modes, leading to an insertion of stray 32-bits of zero in case
the original instruction had the bit set.

Also remove a pointless fall-through in VPEXTRW handling, bringing
things in line with VPINSRW.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Correcting this made me further notice that the SDM states that
VPEXTR{B,W} and VPINSR{B,W} require VEX.W to be clear in other than
their EVEX encodings (which we don't support so far). XED and reality
disagree, so things are being left unchanged there.

--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -6730,10 +6730,9 @@ x86_emulate(
         ea.type = OP_MEM;
         goto simd_0f_int_imm8;
+    CASE_SIMD_PACKED_INT(0x0f, 0xc5):      /* pextrw $imm8,{,x}mm,reg */
     case X86EMUL_OPC_VEX_66(0x0f, 0xc5):   /* vpextrw $imm8,xmm,reg */
         generate_exception_if(vex.l, EXC_UD);
-        /* fall through */
-    CASE_SIMD_PACKED_INT(0x0f, 0xc5):      /* pextrw $imm8,{,x}mm,reg */
         opc = init_prefixes(stub);
         opc[0] = b;
         /* Convert GPR destination to %rAX. */
@@ -7512,6 +7511,8 @@ x86_emulate(
     case X86EMUL_OPC_VEX_66(0x0f3a, 0x20): /* vpinsrb $imm8,r32/m8,xmm,xmm */
     case X86EMUL_OPC_VEX_66(0x0f3a, 0x22): /* vpinsr{d,q} $imm8,r/m,xmm,xmm */
         generate_exception_if(vex.l, EXC_UD);
+        if ( !mode_64bit() )
+            vex.w = 0;
         memcpy(mmvalp, &src.val, op_bytes);
         ea.type = OP_MEM;
         op_bytes = src.bytes;

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