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

From: Vasant Karasulli <vsntk18@gmail.com>
To: x86@kernel.org
Cc: joro@8bytes.org, cfir@google.com, dan.j.williams@intel.com,
	dave.hansen@linux.intel.com, ebiederm@xmission.com,
	erdemaktas@google.com, hpa@zytor.com, jgross@suse.com,
	jslaby@suse.cz, keescook@chromium.org, kexec@lists.infradead.org,
	kvm@vger.kernel.org, linux-coco@lists.linux.dev,
	linux-kernel@vger.kernel.org, luto@kernel.org,
	martin.b.radev@gmail.com, mhiramat@kernel.org,
	mstunes@vmware.com, nivedita@alum.mit.edu, peterz@infradead.org,
	rientjes@google.com, seanjc@google.com, stable@vger.kernel.org,
	thomas.lendacky@amd.com,
	virtualization@lists.linux-foundation.org,
	Joerg Roedel <jroedel@suse.de>,
	Vasant Karasulli <vkarasulli@suse.de>
Subject: [PATCH v4 8/9] x86/sev: Handle CLFLUSH MMIO events
Date: Mon, 11 Mar 2024 17:17:26 +0100	[thread overview]
Message-ID: <20240311161727.14916-9-vsntk18@gmail.com> (raw)
In-Reply-To: <20240311161727.14916-1-vsntk18@gmail.com>

From: Joerg Roedel <jroedel@suse.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@suse.de>
Signed-off-by: Vasant Karasulli <vkarasulli@suse.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


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