linux-kernel - [PATCH 2/2] x86/kexec/64: Forbid kexec when running as an SEV-ES guest

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Message-Id: <20210506093122.28607-3-joro@8bytes.org>
Date:   Thu,  6 May 2021 11:31:22 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Eric Biederman <ebiederm@...ssion.com>, x86@...nel.org
Cc:     kexec@...ts.infradead.org, Joerg Roedel <jroedel@...e.de>,
        stable@...r.kernel.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>,
        Joerg Roedel <joro@...tes.org>, linux-coco@...ts.linux.dev,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: [PATCH 2/2] x86/kexec/64: Forbid kexec when running as an SEV-ES guest

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

For now, kexec is not supported when running as an SEV-ES guest. Doing
so requires additional hypervisor support and special code to hand
over the CPUs to the new kernel in a safe way.

Until this is implemented, do not support kexec in SEV-ES guests.

Cc: stable@...r.kernel.org # v5.10+
Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 arch/x86/kernel/machine_kexec_64.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index c078b0d3ab0e..f902cc9cc634 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -620,3 +620,11 @@ void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages)
 	 */
 	set_memory_encrypted((unsigned long)vaddr, pages);
 }
+
+/*
+ * Kexec is not supported in SEV-ES guests yet
+ */
+bool arch_kexec_supported(void)
+{
+	return !sev_es_active();
+}
-- 
2.31.1