linux-kernel - [PATCH v5 08/10] x86/sev: Handle CLFLUSH MMIO events

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Date: Mon,  8 Apr 2024 09:40:47 +0200
From: vsntk18@...il.com
To: x86@...nel.org
Cc: cfir@...gle.com,
	dan.j.williams@...el.com,
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Subject: [PATCH v5 08/10] x86/sev: Handle CLFLUSH MMIO events

From: Joerg Roedel <jroedel@...e.de>

Handle CLFLUSH instruction to MMIO memory in the #VC handler. The
instruction is ignored by the handler, as the Hypervisor is
responsible for cache management of emulated MMIO memory.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
Signed-off-by: Vasant Karasulli <vkarasulli@...e.de>
---
 arch/x86/include/asm/insn-eval.h | 1 +
 arch/x86/kernel/sev-shared.c     | 3 +++
 arch/x86/lib/insn-eval-shared.c  | 7 +++++++
 3 files changed, 11 insertions(+)

diff --git a/arch/x86/include/asm/insn-eval.h b/arch/x86/include/asm/insn-eval.h
index 54368a43abf6..3bcea641913a 100644
--- a/arch/x86/include/asm/insn-eval.h
+++ b/arch/x86/include/asm/insn-eval.h
@@ -40,6 +40,7 @@ enum insn_mmio_type {
 	INSN_MMIO_READ_ZERO_EXTEND,
 	INSN_MMIO_READ_SIGN_EXTEND,
 	INSN_MMIO_MOVS,
+	INSN_MMIO_IGNORE,
 };
 
 enum insn_mmio_type insn_decode_mmio(struct insn *insn, int *bytes);
diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index d769f80d0264..1bffc2205480 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -1171,6 +1171,9 @@ static enum es_result vc_handle_mmio(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
 	if (mmio == INSN_MMIO_DECODE_FAILED)
 		return ES_DECODE_FAILED;
 
+	if (mmio == INSN_MMIO_IGNORE)
+		return ES_OK;
+
 	if (mmio != INSN_MMIO_WRITE_IMM && mmio != INSN_MMIO_MOVS) {
 		reg_data = insn_get_modrm_reg_ptr(insn, ctxt->regs);
 		if (!reg_data)
diff --git a/arch/x86/lib/insn-eval-shared.c b/arch/x86/lib/insn-eval-shared.c
index 02acdc2921ff..27fd347d84ae 100644
--- a/arch/x86/lib/insn-eval-shared.c
+++ b/arch/x86/lib/insn-eval-shared.c
@@ -906,6 +906,13 @@ enum insn_mmio_type insn_decode_mmio(struct insn *insn, int *bytes)
 				*bytes = 2;
 			type = INSN_MMIO_READ_SIGN_EXTEND;
 			break;
+		case 0xae: /* CLFLUSH */
+			/*
+			 * Ignore CLFLUSHes - those go to emulated MMIO anyway and the
+			 * hypervisor is responsible for cache management.
+			 */
+			type = INSN_MMIO_IGNORE;
+			break;
 		}
 		break;
 	}
-- 
2.34.1