diff mbox series

[SRU,G,v2,3/5] x86/kvm: Disable kvmclock on all CPUs on shutdown

Message ID 20210526051744.218062-4-andrea.righi@canonical.com
State New
Headers show
Series kvm: properly tear down PV features on hibernate | expand

Commit Message

Andrea Righi May 26, 2021, 5:17 a.m. UTC 
From: Vitaly Kuznetsov <vkuznets@redhat.com>

BugLink: https://bugs.launchpad.net/bugs/1920944

Currenly, we disable kvmclock from machine_shutdown() hook and this
only happens for boot CPU. We need to disable it for all CPUs to
guard against memory corruption e.g. on restore from hibernate.

Note, writing '0' to kvmclock MSR doesn't clear memory location, it
just prevents hypervisor from updating the location so for the short
while after write and while CPU is still alive, the clock remains usable
and correct so we don't need to switch to some other clocksource.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210414123544.1060604-4-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit c02027b5742b5aa804ef08a4a9db433295533046)
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
---
 arch/x86/include/asm/kvm_para.h | 4 ++--
 arch/x86/kernel/kvm.c           | 1 +
 arch/x86/kernel/kvmclock.c      | 5 +----
 3 files changed, 4 insertions(+), 6 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 49d3a9edb06f..43cc4a396bee 100644
--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -6,8 +6,6 @@ 
 #include <asm/alternative.h>
 #include <uapi/asm/kvm_para.h>
 
-extern void kvmclock_init(void);
-
 #ifdef CONFIG_KVM_GUEST
 bool kvm_check_and_clear_guest_paused(void);
 #else
@@ -85,6 +83,8 @@  static inline long kvm_hypercall4(unsigned int nr, unsigned long p1,
 }
 
 #ifdef CONFIG_KVM_GUEST
+void kvmclock_init(void);
+void kvmclock_disable(void);
 bool kvm_para_available(void);
 unsigned int kvm_arch_para_features(void);
 unsigned int kvm_arch_para_hints(void);
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 4dc69777417a..74d6c0e344ba 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -438,6 +438,7 @@  static void kvm_guest_cpu_offline(void)
 		wrmsrl(MSR_KVM_PV_EOI_EN, 0);
 	kvm_pv_disable_apf();
 	apf_task_wake_all();
+	kvmclock_disable();
 }
 
 static int kvm_cpu_online(unsigned int cpu)
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 5ee705b44560..327a0de01066 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -221,11 +221,9 @@  static void kvm_crash_shutdown(struct pt_regs *regs)
 }
 #endif
 
-static void kvm_shutdown(void)
+void kvmclock_disable(void)
 {
 	native_write_msr(msr_kvm_system_time, 0, 0);
-	kvm_disable_steal_time();
-	native_machine_shutdown();
 }
 
 static void __init kvmclock_init_mem(void)
@@ -352,7 +350,6 @@  void __init kvmclock_init(void)
 #endif
 	x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
 	x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
-	machine_ops.shutdown  = kvm_shutdown;
 #ifdef CONFIG_KEXEC_CORE
 	machine_ops.crash_shutdown  = kvm_crash_shutdown;
 #endif