[PATCH v6 06/10] x86/sev: Use AP Jump Table blob to stop CPU

vsntk18
2024-06-10T10:21:37Z

To support kexec under SEV-ES the APs can't be parked with HLT. Upon
wakeup the AP needs to find its way to execute at the reset vector set
by the new kernel and in real-mode.

This is what the AP jump table blob provides, so stop the APs the
SEV-ES way by calling the AP-reset-hold VMGEXIT from the AP jump
table.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Vasant Karasulli <vkarasulli@suse.de>
---
arch/x86/include/asm/sev.h | 2 ++
arch/x86/kernel/process.c | 8 ++++++++
arch/x86/kernel/sev.c | 15 ++++++++++++++-
3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 963d51dcf0e6..6f681ced6594 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -232,6 +232,7 @@ 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_show_status(void);
+void sev_es_stop_this_cpu(void);
#else
static inline void sev_es_ist_enter(struct pt_regs *regs) { }
static inline void sev_es_ist_exit(void) { }
@@ -261,6 +262,7 @@ 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_show_status(void) { }
+static inline void sev_es_stop_this_cpu(void) { }
#endif

#ifdef CONFIG_KVM_AMD_SEV
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index b8441147eb5e..0bc615d69c0e 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -52,6 +52,7 @@
#include <asm/tdx.h>
#include <asm/mmu_context.h>
#include <asm/shstk.h>
+#include <asm/sev.h>

#include "process.h"

@@ -836,6 +837,13 @@ void __noreturn stop_this_cpu(void *dummy)
cpumask_clear_cpu(cpu, &cpus_stop_mask);

for (;;) {
+ /*
+ * SEV-ES guests need a special stop routine to support
+ * kexec. Try this first, if it fails the function will
+ * return and native_halt() is used.
+ */
+ sev_es_stop_this_cpu();
+
/*
* Use native_halt() so that memory contents don't change
* (stack usage and variables) after possibly issuing the
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 84b79630f065..8d3cc5cd7e11 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -1357,7 +1357,6 @@ void setup_ghcb(void)
snp_register_ghcb_early(__pa(&boot_ghcb_page));
}

-#ifdef CONFIG_HOTPLUG_CPU
void __noreturn sev_jumptable_ap_park(void)
{
local_irq_disable();
@@ -1390,6 +1389,20 @@ void __noreturn sev_jumptable_ap_park(void)
}
STACK_FRAME_NON_STANDARD(sev_jumptable_ap_park);

+void sev_es_stop_this_cpu(void)
+{
+ if (!(cc_vendor == CC_VENDOR_AMD) ||
+ !cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
+ return;
+
+ /* Only park in the AP jump table when the code has been installed */
+ if (!sev_ap_jumptable_blob_installed)
+ return;
+
+ sev_jumptable_ap_park();
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
static void sev_es_ap_hlt_loop(void)
{
struct ghcb_state state;
--
2.34.1