linux-kernel - [PATCH 12/16] KVM: emulate: Reject EVEX-prefixed instructions

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Message-ID: <20251221040742.29749-13-chang.seok.bae@intel.com>
Date: Sun, 21 Dec 2025 04:07:38 +0000
From: "Chang S. Bae" <chang.seok.bae@...el.com>
To: pbonzini@...hat.com,
	seanjc@...gle.com
Cc: kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	chao.gao@...el.com,
	chang.seok.bae@...el.com
Subject: [PATCH 12/16] KVM: emulate: Reject EVEX-prefixed instructions

Explicitly mark EVEX-prefixed opcodes (0x62) as unsupported.

Signed-off-by: Chang S. Bae <chang.seok.bae@...el.com>
---
Changes since last version:
* Rebase onto the recently merged VEX series. Reuse the previously existing
  VEX-rejection logic and style.
---
 arch/x86/kvm/emulate.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index fc065ef53400..820ae381e601 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -5040,6 +5040,11 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len, int
 	if (ctxt->d & NoRex && ctxt->rex_prefix == REX2_PREFIX)
 		opcode.flags = Undefined;
 
+	/* EVEX-prefixed instructions are not implemented */
+	if (ctxt->opcode_len == 1 && ctxt->b == 0x62 &&
+	    (mode == X86EMUL_MODE_PROT64 || (ctxt->modrm & 0xc0) == 0xc0))
+		opcode.flags = NotImpl;
+
 	if (opcode.flags & ModRM)
 		ctxt->modrm = insn_fetch(u8, ctxt);
 
-- 
2.51.0