Commit 3d6b8413 authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Paolo Bonzini
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x86/kvm: Disable all PV features on crash 



Crash shutdown handler only disables kvmclock and steal time, other PV
features remain active so we risk corrupting memory or getting some
side-effects in kdump kernel. Move crash handler to kvm.c and unify
with CPU offline.

Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210414123544.1060604-5-vkuznets@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent c02027b5

arch/x86/include/asm/kvm_para.h

+0 −6
Original line number Diff line number Diff line
@@ -92,7 +92,6 @@ unsigned int kvm_arch_para_hints(void); 
void kvm_async_pf_task_wait_schedule(u32 token);

void kvm_async_pf_task_wake(u32 token);

u32 kvm_read_and_reset_apf_flags(void);

void kvm_disable_steal_time(void);

bool __kvm_handle_async_pf(struct pt_regs *regs, u32 token);



DECLARE_STATIC_KEY_FALSE(kvm_async_pf_enabled);
@@ -137,11 +136,6 @@ static inline u32 kvm_read_and_reset_apf_flags(void) 
	return 0;

}



static inline void kvm_disable_steal_time(void)

{

	return;

}



static __always_inline bool kvm_handle_async_pf(struct pt_regs *regs, u32 token)

{

	return false;

arch/x86/kernel/kvm.c

+32 −12
Original line number Diff line number Diff line
@@ -38,6 +38,7 @@ 
#include <asm/tlb.h>

#include <asm/cpuidle_haltpoll.h>

#include <asm/ptrace.h>

#include <asm/reboot.h>

#include <asm/svm.h>



DEFINE_STATIC_KEY_FALSE(kvm_async_pf_enabled);
@@ -375,6 +376,14 @@ static void kvm_pv_disable_apf(void) 
	pr_info("disable async PF for cpu %d\n", smp_processor_id());

}



static void kvm_disable_steal_time(void)

{

	if (!has_steal_clock)

		return;



	wrmsr(MSR_KVM_STEAL_TIME, 0, 0);

}



static void kvm_pv_guest_cpu_reboot(void *unused)

{

	/*
@@ -417,14 +426,6 @@ static u64 kvm_steal_clock(int cpu) 
	return steal;

}



void kvm_disable_steal_time(void)

{

	if (!has_steal_clock)

		return;



	wrmsr(MSR_KVM_STEAL_TIME, 0, 0);

}



static inline void __set_percpu_decrypted(void *ptr, unsigned long size)

{

	early_set_memory_decrypted((unsigned long) ptr, size);
@@ -452,12 +453,13 @@ static void __init sev_map_percpu_data(void) 
	}

}



static void kvm_guest_cpu_offline(void)

static void kvm_guest_cpu_offline(bool shutdown)

{

	kvm_disable_steal_time();

	if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))

		wrmsrl(MSR_KVM_PV_EOI_EN, 0);

	kvm_pv_disable_apf();

	if (!shutdown)

		apf_task_wake_all();

	kvmclock_disable();

}
@@ -661,7 +663,7 @@ static int kvm_cpu_down_prepare(unsigned int cpu) 
	unsigned long flags;



	local_irq_save(flags);

	kvm_guest_cpu_offline();

	kvm_guest_cpu_offline(false);

	local_irq_restore(flags);

	return 0;

}
@@ -670,7 +672,7 @@ static int kvm_cpu_down_prepare(unsigned int cpu) 


static int kvm_suspend(void)

{

	kvm_guest_cpu_offline();

	kvm_guest_cpu_offline(false);



	return 0;

}
@@ -685,6 +687,20 @@ static struct syscore_ops kvm_syscore_ops = { 
	.resume		= kvm_resume,

};



/*

 * After a PV feature is registered, the host will keep writing to the

 * registered memory location. If the guest happens to shutdown, this memory

 * won't be valid. In cases like kexec, in which you install a new kernel, this

 * means a random memory location will be kept being written.

 */

#ifdef CONFIG_KEXEC_CORE

static void kvm_crash_shutdown(struct pt_regs *regs)

{

	kvm_guest_cpu_offline(true);

	native_machine_crash_shutdown(regs);

}

#endif



static void __init kvm_guest_init(void)

{

	int i;
@@ -727,6 +743,10 @@ static void __init kvm_guest_init(void) 
	kvm_guest_cpu_init();

#endif



#ifdef CONFIG_KEXEC_CORE

	machine_ops.crash_shutdown = kvm_crash_shutdown;

#endif



	register_syscore_ops(&kvm_syscore_ops);



	/*

arch/x86/kernel/kvmclock.c

+0 −21
Original line number Diff line number Diff line
@@ -20,7 +20,6 @@ 
#include <asm/hypervisor.h>

#include <asm/mem_encrypt.h>

#include <asm/x86_init.h>

#include <asm/reboot.h>

#include <asm/kvmclock.h>



static int kvmclock __initdata = 1;
@@ -203,23 +202,6 @@ static void kvm_setup_secondary_clock(void) 
}

#endif



/*

 * After the clock is registered, the host will keep writing to the

 * registered memory location. If the guest happens to shutdown, this memory

 * won't be valid. In cases like kexec, in which you install a new kernel, this

 * means a random memory location will be kept being written. So before any

 * kind of shutdown from our side, we unregister the clock by writing anything

 * that does not have the 'enable' bit set in the msr

 */

#ifdef CONFIG_KEXEC_CORE

static void kvm_crash_shutdown(struct pt_regs *regs)

{

	native_write_msr(msr_kvm_system_time, 0, 0);

	kvm_disable_steal_time();

	native_machine_crash_shutdown(regs);

}

#endif



void kvmclock_disable(void)

{

	native_write_msr(msr_kvm_system_time, 0, 0);
@@ -349,9 +331,6 @@ 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;

#ifdef CONFIG_KEXEC_CORE

	machine_ops.crash_shutdown  = kvm_crash_shutdown;

#endif

	kvm_get_preset_lpj();



	/*