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Subject[PATCH v7 69/72] x86/sev-es: Support CPU offline/online
Date
From: Joerg Roedel <jroedel@suse.de>

Add a play_dead handler when running under SEV-ES. This is needed
because the hypervisor can't deliver an SIPI request to restart the AP.
Instead the kernel has to issue a VMGEXIT to halt the VCPU until the
hypervisor wakes it up again.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
arch/x86/include/uapi/asm/svm.h | 1 +
arch/x86/kernel/sev-es.c | 63 +++++++++++++++++++++++++++++++++
2 files changed, 64 insertions(+)

diff --git a/arch/x86/include/uapi/asm/svm.h b/arch/x86/include/uapi/asm/svm.h
index 346b8a7155e8..c1dcf3e114e4 100644
--- a/arch/x86/include/uapi/asm/svm.h
+++ b/arch/x86/include/uapi/asm/svm.h
@@ -84,6 +84,7 @@
/* SEV-ES software-defined VMGEXIT events */
#define SVM_VMGEXIT_MMIO_READ 0x80000001
#define SVM_VMGEXIT_MMIO_WRITE 0x80000002
+#define SVM_VMGEXIT_AP_HLT_LOOP 0x80000004
#define SVM_VMGEXIT_AP_JUMP_TABLE 0x80000005
#define SVM_VMGEXIT_SET_AP_JUMP_TABLE 0
#define SVM_VMGEXIT_GET_AP_JUMP_TABLE 1
diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index 91e32172d355..0b6c4f46ddfc 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -29,6 +29,8 @@
#include <asm/realmode.h>
#include <asm/traps.h>
#include <asm/svm.h>
+#include <asm/smp.h>
+#include <asm/cpu.h>

#define DR7_RESET_VALUE 0x400

@@ -518,6 +520,65 @@ static bool __init sev_es_setup_ghcb(void)
return true;
}

+#ifdef CONFIG_HOTPLUG_CPU
+static void sev_es_ap_hlt_loop(void)
+{
+ struct ghcb_state state;
+ struct ghcb *ghcb;
+
+ ghcb = sev_es_get_ghcb(&state);
+
+ while (true) {
+ vc_ghcb_invalidate(ghcb);
+ ghcb_set_sw_exit_code(ghcb, SVM_VMGEXIT_AP_HLT_LOOP);
+ ghcb_set_sw_exit_info_1(ghcb, 0);
+ ghcb_set_sw_exit_info_2(ghcb, 0);
+
+ sev_es_wr_ghcb_msr(__pa(ghcb));
+ VMGEXIT();
+
+ /* Wakeup signal? */
+ if (ghcb_sw_exit_info_2_is_valid(ghcb) &&
+ ghcb->save.sw_exit_info_2)
+ break;
+ }
+
+ sev_es_put_ghcb(&state);
+}
+
+/*
+ * Play_dead handler when running under SEV-ES. This is needed because
+ * the hypervisor can't deliver an SIPI request to restart the AP.
+ * Instead the kernel has to issue a VMGEXIT to halt the VCPU until the
+ * hypervisor wakes it up again.
+ */
+static void sev_es_play_dead(void)
+{
+ play_dead_common();
+
+ /* IRQs now disabled */
+
+ sev_es_ap_hlt_loop();
+
+ /*
+ * If we get here, the VCPU was woken up again. Jump to CPU
+ * startup code to get it back online.
+ */
+ start_cpu0();
+}
+#else /* CONFIG_HOTPLUG_CPU */
+#define sev_es_play_dead native_play_dead
+#endif /* CONFIG_HOTPLUG_CPU */
+
+#ifdef CONFIG_SMP
+static void __init sev_es_setup_play_dead(void)
+{
+ smp_ops.play_dead = sev_es_play_dead;
+}
+#else
+static inline void sev_es_setup_play_dead(void) { }
+#endif
+
static void __init alloc_runtime_data(int cpu)
{
struct sev_es_runtime_data *data;
@@ -566,6 +627,8 @@ void __init sev_es_init_vc_handling(void)
setup_vc_stacks(cpu);
}

+ sev_es_setup_play_dead();
+
/* Secondary CPUs use the runtime #VC handler */
initial_vc_handler = (unsigned long)safe_stack_exc_vmm_communication;
}
--
2.28.0
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