linux-kernel - [PATCH v4 8/9] x86/sev: Handle CLFLUSH MMIO events

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Date: Mon, 11 Mar 2024 17:17:26 +0100
From: Vasant Karasulli <vsntk18@...il.com>
To: x86@...nel.org
Cc: joro@...tes.org,
	cfir@...gle.com,
	dan.j.williams@...el.com,
	dave.hansen@...ux.intel.com,
	ebiederm@...ssion.com,
	erdemaktas@...gle.com,
	hpa@...or.com,
	jgross@...e.com,
	jslaby@...e.cz,
	keescook@...omium.org,
	kexec@...ts.infradead.org,
	kvm@...r.kernel.org,
	linux-coco@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	luto@...nel.org,
	martin.b.radev@...il.com,
	mhiramat@...nel.org,
	mstunes@...are.com,
	nivedita@...m.mit.edu,
	peterz@...radead.org,
	rientjes@...gle.com,
	seanjc@...gle.com,
	stable@...r.kernel.org,
	thomas.lendacky@....com,
	virtualization@...ts.linux-foundation.org,
	Joerg Roedel <jroedel@...e.de>,
	Vasant Karasulli <vkarasulli@...e.de>
Subject: [PATCH v4 8/9] 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 e9a959c1c11d..ac0704055d58 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -1164,6 +1164,9 @@ 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 efc9755573db..3d71a947e562 100644
--- a/arch/x86/lib/insn-eval-shared.c
+++ b/arch/x86/lib/insn-eval-shared.c
@@ -897,6 +897,13 @@ 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