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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>
This commit is contained in:
Vitaly Kuznetsov 2021-05-31 16:03:46 +02:00 committed by Greg Kroah-Hartman
parent 7620a66911
commit 9084fe1b35
3 changed files with 4 additions and 6 deletions
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4
arch/x86/include/asm/kvm_para.h
View File

@ -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);

1
arch/x86/kernel/kvm.c
View File

@ -436,6 +436,7 @@ 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)

5
arch/x86/kernel/kvmclock.c
View File

@ -214,11 +214,9 @@ 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)
@ -346,7 +344,6 @@ 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