x86/kvm: Disable kvmclock on all CPUs on shutdown

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>

diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 338119852512654b51d6c01befa7af58e6621782..9c56e0defd4532c0945772fef25388db44684d5d 100644 (file)
--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -7,8 +7,6 @@
 #include <linux/interrupt.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
@@ -86,6 +84,8 @@ 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 9d5f96321c7f9ef39302194a6e90796fb6e6719f..25dd126a332504f7c407743a52a332ebaf9913b3 100644 (file)
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -459,6 +459,7 @@ 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 d37ed4e1d0338c8b21ad461f5d2672cead15629a..081686df6cd8aba611d638f18ce72202fa4d0d10 100644 (file)
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -220,11 +220,9 @@ 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)
@@ -351,7 +349,6 @@ 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