linux-kernel - [PATCH v3 63/75] x86/sev-es: Handle #DB Events

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Message-Id: <20200428151725.31091-64-joro@8bytes.org>
Date:   Tue, 28 Apr 2020 17:17:13 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     x86@...nel.org
Cc:     hpa@...or.com, Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Hellstrom <thellstrom@...are.com>,
        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>,
        Joerg Roedel <joro@...tes.org>, Joerg Roedel <jroedel@...e.de>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: [PATCH v3 63/75] x86/sev-es: Handle #DB Events

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

Handle #VC exceptions caused by #DB exceptions in the guest. Do not
forward them to the hypervisor and handle them with do_debug() instead.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 arch/x86/kernel/sev-es.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index 050a15da9ae5..03095bc7b563 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -882,6 +882,19 @@ static enum es_result vc_handle_trap_ac(struct ghcb *ghcb,
 	return ES_EXCEPTION;
 }
 
+static enum es_result vc_handle_trap_db(struct ghcb *ghcb,
+					struct es_em_ctxt *ctxt)
+{
+	/*
+	 * Calling do_debug() directly does not work, because it might enable
+	 * IRQs and the GHCB is active. Forward the exception and call it later
+	 * from vc_forward_exception().
+	 */
+	ctxt->fi.vector = X86_TRAP_DB;
+	ctxt->fi.error_code = 0;
+	return ES_EXCEPTION;
+}
+
 static enum es_result vc_handle_exitcode(struct es_em_ctxt *ctxt,
 					 struct ghcb *ghcb,
 					 unsigned long exit_code)
@@ -895,6 +908,9 @@ static enum es_result vc_handle_exitcode(struct es_em_ctxt *ctxt,
 	case SVM_EXIT_WRITE_DR7:
 		result = vc_handle_dr7_write(ghcb, ctxt);
 		break;
+	case SVM_EXIT_EXCP_BASE + X86_TRAP_DB:
+		result = vc_handle_trap_db(ghcb, ctxt);
+		break;
 	case SVM_EXIT_EXCP_BASE + X86_TRAP_AC:
 		result = vc_handle_trap_ac(ghcb, ctxt);
 		break;
@@ -960,6 +976,9 @@ static void vc_forward_exception(struct es_em_ctxt *ctxt)
 	case X86_TRAP_AC:
 		do_alignment_check(ctxt->regs, error_code);
 		break;
+	case X86_TRAP_DB:
+		do_debug(ctxt->regs, error_code);
+		break;
 	default:
 		pr_emerg("Unsupported exception in #VC instruction emulation - can't continue\n");
 		BUG();
-- 
2.17.1