Commit c02027b5 authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Paolo Bonzini
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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: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210414123544.1060604-4-vkuznets@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 8b79feff

arch/x86/include/asm/kvm_para.h

+2 −2
Original line number Diff line number Diff line
@@ -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);

arch/x86/kernel/kvm.c

+1 −0
Original line number Diff line number Diff line
@@ -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)

arch/x86/kernel/kvmclock.c

+1 −4
Original line number Diff line number Diff line
@@ -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