linux-kernel - [PATCH] x86/sev-es: Fix SEV-ES OUT/IN immediate opcode vc handling

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Date:   Wed, 16 Dec 2020 17:04:09 -0800
From:   Peter Gonda <pgonda@...gle.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>
Cc:     Peter Gonda <pgonda@...gle.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        David Rientjes <rientjes@...gle.com>
Subject: [PATCH] x86/sev-es: Fix SEV-ES OUT/IN immediate opcode vc handling


The IN and OUT immediate instructions only use an 8-bit immediate. The
current VC handler uses the entire 32-bit immediate value. These
instructions only set the first bytes.

Tested with a loop back port with "outb %0,$0xe0". Before the port seen
by KVM was 0xffffffffffffffe0 instead of 0xe0. After the correct port
was seen by KVM and the guests loop back OUT then IN were equal.


Signed-off-by: Peter Gonda <pgonda@...gle.com>
Acked-by: David Rientjes <rientjes@...gle.com>


---
 arch/x86/kernel/sev-es-shared.c | 8 ++++++--
 drivers/Makefile                | 1 +
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/sev-es-shared.c b/arch/x86/kernel/sev-es-shared.c
index 7d04b356d44d..6c790377c55c 100644
--- a/arch/x86/kernel/sev-es-shared.c
+++ b/arch/x86/kernel/sev-es-shared.c
@@ -305,14 +305,14 @@ static enum es_result vc_ioio_exitinfo(struct es_em_ctxt *ctxt, u64 *exitinfo)
 	case 0xe4:
 	case 0xe5:
 		*exitinfo |= IOIO_TYPE_IN;
-		*exitinfo |= (u64)insn->immediate.value << 16;
+		*exitinfo |= insn->immediate.bytes[0] << 16;
 		break;
 
 	/* OUT immediate opcodes */
 	case 0xe6:
 	case 0xe7:
 		*exitinfo |= IOIO_TYPE_OUT;
-		*exitinfo |= (u64)insn->immediate.value << 16;
+		*exitinfo |= insn->immediate.bytes[0] << 16;
 		break;