linux-kernel - [PATCH v6 09/10] x86/kexec/64: Support kexec under SEV-ES with AP Jump Table Blob

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Date: Mon, 10 Jun 2024 12:21:12 +0200
From: vsntk18@...il.com
To: vsntk18@...il.com
Cc: x86@...nel.org,
	Borislav.Petkov@....com,
	Dhaval.Giani@....com,
	ashish.kalra@....com,
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	jroedel@...e.de,
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	keescook@...omium.org,
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	vkarasulli@...e.de
Subject: [PATCH v6 09/10] 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>
Signed-off-by: Vasant Karasulli <vkarasulli@...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 6f681ced6594..e557eadb0ec9 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -233,6 +233,7 @@ u64 snp_get_unsupported_features(u64 status);
 u64 sev_get_status(void);
 void sev_show_status(void);
 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) { }
@@ -263,6 +264,7 @@ static inline u64 snp_get_unsupported_features(u64 status) { return 0; }
 static inline u64 sev_get_status(void) { return 0; }
 static inline void sev_show_status(void) { }
 static inline void sev_es_stop_this_cpu(void) { }
+static inline bool sev_kexec_supported(void) { return true; }
 #endif
 
 #ifdef CONFIG_KVM_AMD_SEV
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 1dfb47df5c01..43f5f7e48cbc 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -28,6 +28,7 @@
 #include <asm/setup.h>
 #include <asm/set_memory.h>
 #include <asm/cpu.h>
+#include <asm/sev.h>
 
 #ifdef CONFIG_ACPI
 /*
@@ -269,7 +270,7 @@ 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 30ede17b5a04..e64320507da2 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -1463,6 +1463,21 @@ static void __init sev_es_setup_play_dead(void)
 static inline void sev_es_setup_play_dead(void) { }
 #endif
 
+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