From: Vitaly Kuznetsov <vkuznets@redhat.com>
Date: Wed, 14 Apr 2021 14:35:41 +0200
Subject: x86/kvm: Teardown PV features on boot CPU as well
Patch-mainline: v5.13-rc2
Git-commit: 8b79feffeca28c5459458fe78676b081e87c93a4
References: bsc#1185308

Various PV features (Async PF, PV EOI, steal time) work through memory
shared with hypervisor and when we restore from hibernation we must
properly teardown all these features to make sure hypervisor doesn't
write to stale locations after we jump to the previously hibernated kernel
(which can try to place anything there). For secondary CPUs the job is
already done by kvm_cpu_down_prepare(), register syscore ops to do
the same for boot CPU.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210414123544.1060604-3-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Liang Yan <lyan@suse.com>
---
 arch/x86/kernel/kvm.c |   56 +++++++++++++++++++++++++++++++++++---------------
 1 file changed, 40 insertions(+), 16 deletions(-)

--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -37,6 +37,7 @@
 #include <linux/debugfs.h>
 #include <linux/nmi.h>
 #include <linux/swait.h>
+#include <linux/syscore_ops.h>
 #include <asm/timer.h>
 #include <asm/cpu.h>
 #include <asm/traps.h>
@@ -453,6 +454,25 @@ static void __init sev_map_percpu_data(v
 	}
 }
 
+static void kvm_guest_cpu_offline(void)
+{
+	kvm_disable_steal_time();
+	if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
+		wrmsrl(MSR_KVM_PV_EOI_EN, 0);
+	kvm_pv_disable_apf();
+	apf_task_wake_all();
+}
+
+static int kvm_cpu_online(unsigned int cpu)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	kvm_guest_cpu_init();
+	local_irq_restore(flags);
+	return 0;	
+}
+
 #ifdef CONFIG_SMP
 static void __init kvm_smp_prepare_boot_cpu(void)
 {
@@ -467,31 +487,33 @@ static void __init kvm_smp_prepare_boot_
 	kvm_spinlock_init();
 }
 
-static void kvm_guest_cpu_offline(void)
+static int kvm_cpu_down_prepare(unsigned int cpu)
 {
-	kvm_disable_steal_time();
-	if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
-		wrmsrl(MSR_KVM_PV_EOI_EN, 0);
-	kvm_pv_disable_apf();
-	apf_task_wake_all();
-}
+	unsigned long flags;
 
-static int kvm_cpu_online(unsigned int cpu)
-{
-	local_irq_disable();
-	kvm_guest_cpu_init();
-	local_irq_enable();
+	local_irq_save(flags);
+	kvm_guest_cpu_offline();
+	local_irq_restore(flags);
 	return 0;
 }
+#endif
 
-static int kvm_cpu_down_prepare(unsigned int cpu)
+static int kvm_suspend(void)
 {
-	local_irq_disable();
 	kvm_guest_cpu_offline();
-	local_irq_enable();
+
 	return 0;
 }
-#endif
+
+static void kvm_resume(void)
+{
+	kvm_cpu_online(raw_smp_processor_id());
+}
+
+static struct syscore_ops kvm_syscore_ops = {
+	.suspend	= kvm_suspend,
+	.resume		= kvm_resume,
+};
 
 static void __init kvm_apf_trap_init(void)
 {
@@ -533,6 +555,8 @@ void __init kvm_guest_init(void)
 	kvm_guest_cpu_init();
 #endif
 
+	register_syscore_ops(&kvm_syscore_ops);
+
 	/*
 	 * Hard lockup detection is enabled by default. Disable it, as guests
 	 * can get false positives too easily, for example if the host is