diff mbox series

[SRU,G,2/5] x86/kvm: Teardown PV features on boot CPU as well

Message ID 20210520133948.39779-3-andrea.righi@canonical.com
State New
Headers show
Series kvm: properly tear down PV features on hibernate | expand

Commit Message

Andrea Righi May 20, 2021, 1:39 p.m. UTC 
From: Vitaly Kuznetsov <vkuznets@redhat.com>

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>
(backported from commit 8b79feffeca28c5459458fe78676b081e87c93a4)
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
---
 arch/x86/kernel/kvm.c | 57 +++++++++++++++++++++++++++++++------------
 1 file changed, 41 insertions(+), 16 deletions(-)

Comments

Krzysztof Kozlowski May 20, 2021, 5:32 p.m. UTC | #1 
On 20/05/2021 09:39, Andrea Righi wrote:
> From: Vitaly Kuznetsov <vkuznets@redhat.com>
> 
> 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>
> (backported from commit 8b79feffeca28c5459458fe78676b081e87c93a4)
> Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
> ---
>  arch/x86/kernel/kvm.c | 57 +++++++++++++++++++++++++++++++------------
>  1 file changed, 41 insertions(+), 16 deletions(-)
> 


For the same reasons as focal - backport is quite different and the
kvm_guest_cpu_offline() location looks now wrong. This might not build
on !SMP, similarly as on Focal.

Best regards,
Krzysztof
diff mbox series

Patch

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 0fee42222a8f..4dc69777417a 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -23,6 +23,7 @@ 
 #include <linux/kprobes.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>
@@ -430,6 +431,25 @@  static void __init sev_map_percpu_data(void)
 	}
 }
 
+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;
+}
+
 static bool pv_tlb_flush_supported(void)
 {
 	return (kvm_para_has_feature(KVM_FEATURE_PV_TLB_FLUSH) &&
@@ -571,31 +591,34 @@  static void __init kvm_smp_prepare_boot_cpu(void)
 	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;
 }
 
-static int kvm_cpu_down_prepare(unsigned int cpu)
+#endif
+
+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 kvm_flush_tlb_others(const struct cpumask *cpumask,
 			const struct flush_tlb_info *info)
@@ -664,6 +687,8 @@  static 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