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target/i386/tcg: allow VEX in 16-bit protected mode

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VEX is only forbidden in real and vm86 mode; 16-bit protected mode supports
it for some unfathomable reason.

Cc: qemu-stable@nongnu.org
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit ed88bdcfbdcf9d411607cd690f93f915feff6a5b)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
This commit is contained in:
Paolo Bonzini 2025-12-12 18:06:45 +01:00 • committed by Michael Tokarev
parent 6594e50e7e
commit 11e286fb93
1 changed files with 3 additions and 7 deletions
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10
target/i386/tcg/decode-new.c.inc
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@ -2613,20 +2613,16 @@ static void disas_insn(DisasContext *s, CPUState *cpu)
case 0xc5: /* 2-byte VEX */
case 0xc4: /* 3-byte VEX */
/*
* VEX prefixes cannot be used except in 32-bit mode.
* Otherwise the instruction is LES or LDS.
* Bits 6-7 of the first byte must be set except in 64-bit mode.
* Otherwise the instruction is LES or LDS. Not allowed in real mode.
*/
if (CODE32(s) && !VM86(s)) {
if (PE(s) && !VM86(s)) {
static const int pp_prefix[4] = {
0, PREFIX_DATA, PREFIX_REPZ, PREFIX_REPNZ
};
int vex3, vex2 = x86_ldub_code(env, s);
if (!CODE64(s) && (vex2 & 0xc0) != 0xc0) {
/*
* 4.1.4.6: In 32-bit mode, bits [7:6] must be 11b,
* otherwise the instruction is LES or LDS.
*/
s->pc--; /* rewind the advance_pc() x86_ldub_code() did */
break;
}