linux-kernel - [PATCH v4 9/9] x86/kexec/64: Support kexec under SEV-ES with AP Jump Table Blob

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Message-Id: <20240311161727.14916-10-vsntk18@gmail.com>
Date: Mon, 11 Mar 2024 17:17:27 +0100
From: Vasant Karasulli <vsntk18@...il.com>
To: x86@...nel.org
Cc: joro@...tes.org,
	cfir@...gle.com,
	dan.j.williams@...el.com,
	dave.hansen@...ux.intel.com,
	ebiederm@...ssion.com,
	erdemaktas@...gle.com,
	hpa@...or.com,
	jgross@...e.com,
	jslaby@...e.cz,
	keescook@...omium.org,
	kexec@...ts.infradead.org,
	kvm@...r.kernel.org,
	linux-coco@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	luto@...nel.org,
	martin.b.radev@...il.com,
	mhiramat@...nel.org,
	mstunes@...are.com,
	nivedita@...m.mit.edu,
	peterz@...radead.org,
	rientjes@...gle.com,
	seanjc@...gle.com,
	stable@...r.kernel.org,
	thomas.lendacky@....com,
	virtualization@...ts.linux-foundation.org,
	Joerg Roedel <jroedel@...e.de>,
	Vasant Karasulli <vkarasulli@...e.de>
Subject: [PATCH v4 9/9] 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 2dbd2238325a..26027083a2a9 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -217,6 +217,7 @@ void snp_accept_memory(phys_addr_t start, phys_addr_t end);
 u64 snp_get_unsupported_features(u64 status);
 u64 sev_get_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) { }
@@ -246,6 +247,7 @@ static inline void snp_accept_memory(phys_addr_t start, phys_addr_t end) { }
 static inline u64 snp_get_unsupported_features(u64 status) { return 0; }
 static inline u64 sev_get_status(void) { 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 3671ea1a5045..6013ba6fc16e 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 73477eeb7de2..66e85b82d170 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -1456,6 +1456,21 @@ 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