linux-kernel - [PATCH v3 09/10] x86/sev: Handle CLFLUSH MMIO events

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Message-Id: <20220127101044.13803-10-joro@8bytes.org>
Date:   Thu, 27 Jan 2022 11:10:43 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     x86@...nel.org
Cc:     Joerg Roedel <joro@...tes.org>, Joerg Roedel <jroedel@...e.de>,
        Eric Biederman <ebiederm@...ssion.com>,
        kexec@...ts.infradead.org, hpa@...or.com,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Martin Radev <martin.b.radev@...il.com>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: [PATCH v3 09/10] 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>
---
 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 f07faa61c7f3..c3eb753a912b 100644
--- a/arch/x86/include/asm/insn-eval.h
+++ b/arch/x86/include/asm/insn-eval.h
@@ -40,6 +40,7 @@ enum mmio_type {
 	MMIO_READ_ZERO_EXTEND,
 	MMIO_READ_SIGN_EXTEND,
 	MMIO_MOVS,
+	MMIO_IGNORE,
 };
 
 enum 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 b12fb063a30e..1aa33509c7b5 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -698,6 +698,9 @@ static enum es_result vc_handle_mmio(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
 	if (mmio == MMIO_DECODE_FAILED)
 		return ES_DECODE_FAILED;
 
+	if (mmio == MMIO_IGNORE)
+		return ES_OK;
+
 	if (mmio != MMIO_WRITE_IMM && mmio != 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 ec310b5e6cd5..ddec72fccdd2 100644
--- a/arch/x86/lib/insn-eval-shared.c
+++ b/arch/x86/lib/insn-eval-shared.c
@@ -898,6 +898,13 @@ enum mmio_type insn_decode_mmio(struct insn *insn, int *bytes)
 				*bytes = 2;
 			type = 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 = MMIO_IGNORE;
+			break;
 		}
 		break;
 	}
-- 
2.34.1