linux-kernel - [PATCH v3 10/10] x86/kexec/64: Support kexec under SEV-ES with AP Jump Table Blob

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Message-Id: <20220127101044.13803-11-joro@8bytes.org>
Date:   Thu, 27 Jan 2022 11:10:44 +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 10/10] x86/kexec/64: Support kexec under SEV-ES with AP Jump Table Blob

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

When the AP jump table blob is installed the kernel can hand over the
APs from the old to the new kernel. Enable kexec when the AP jump
table blob has been installed.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 arch/x86/include/asm/sev.h         |  2 ++
 arch/x86/kernel/machine_kexec_64.c |  3 ++-
 arch/x86/kernel/sev.c              | 15 +++++++++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index e342dce3e7a1..41e07d037b6e 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -91,6 +91,7 @@ extern enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
 					  u64 exit_code, u64 exit_info_1,
 					  u64 exit_info_2);
 void sev_es_stop_this_cpu(void);
+bool sev_kexec_supported(void);
 #else
 static inline void sev_es_ist_enter(struct pt_regs *regs) { }
 static inline void sev_es_ist_exit(void) { }
@@ -98,6 +99,7 @@ static inline int sev_es_setup_ap_jump_table(struct real_mode_header *rmh) { ret
 static inline void sev_es_nmi_complete(void) { }
 static inline int sev_es_efi_map_ghcbs(pgd_t *pgd) { return 0; }
 static inline void sev_es_stop_this_cpu(void) { }
+static inline bool sev_kexec_supported(void) { return true; }
 #endif
 
 #endif
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 5079a75f8944..c58808fe3fb5 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -27,6 +27,7 @@
 #include <asm/kexec-bzimage64.h>
 #include <asm/setup.h>
 #include <asm/set_memory.h>
+#include <asm/sev.h>
 
 #ifdef CONFIG_ACPI
 /*
@@ -271,7 +272,7 @@ static void load_segments(void)
 
 static bool machine_kexec_supported(void)
 {
-	if (cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
+	if (!sev_kexec_supported())
 		return false;
 
 	return true;
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 1bced5b49150..17dcbcddd6ab 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -884,6 +884,21 @@ static int __init sev_setup_ap_jump_table(void)
 }
 core_initcall(sev_setup_ap_jump_table);
 
+bool sev_kexec_supported(void)
+{
+	if (!cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
+		return true;
+
+	/*
+	 * KEXEC with SEV-ES and more than one CPU is only supported
+	 * when the AP jump table is installed.
+	 */
+	if (num_possible_cpus() > 1)
+		return sev_ap_jumptable_blob_installed;
+	else
+		return true;
+}
+
 static void __init alloc_runtime_data(int cpu)
 {
 	struct sev_es_runtime_data *data;
-- 
2.34.1