x86/kvm: Disable kvmclock on all CPUs on shutdown

commit c02027b5742b5aa804ef08a4a9db433295533046 upstream.

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>
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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 6af3f9c3956c92a197a74b8f2f8bf0468baa0edd..be1c42e663c65d35e3b2d4ffcc2125e86df2b99d 100644 (file)
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -468,6 +468,7 @@ 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 5ee705b44560b54c123200446eeb6a6890a51a73..327a0de010668a2750e17dd3861367b0d988fcf8 100644 (file)
--- 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