Commit dfe94d40 authored by Dexuan Cui's avatar Dexuan Cui Committed by Wei Liu
Browse files

x86/hyperv: Fix kexec panic/hang issues 



Currently the kexec kernel can panic or hang due to 2 causes:

1) hv_cpu_die() is not called upon kexec, so the hypervisor corrupts the
old VP Assist Pages when the kexec kernel runs. The same issue is fixed
for hibernation in commit 421f090c ("x86/hyperv: Suspend/resume the
VP assist page for hibernation"). Now fix it for kexec.

2) hyperv_cleanup() is called too early. In the kexec path, the other CPUs
are stopped in hv_machine_shutdown() -> native_machine_shutdown(), so
between hv_kexec_handler() and native_machine_shutdown(), the other CPUs
can still try to access the hypercall page and cause panic. The workaround
"hv_hypercall_pg = NULL;" in hyperv_cleanup() is unreliabe. Move
hyperv_cleanup() to a better place.

Signed-off-by: default avatarDexuan Cui <decui@microsoft.com>
Reviewed-by: default avatarMichael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20201222065541.24312-1-decui@microsoft.com


Signed-off-by: default avatarWei Liu <wei.liu@kernel.org>
parent e71ba945

arch/x86/hyperv/hv_init.c

+4 −0
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#include <asm/hyperv-tlfs.h>

#include <asm/mshyperv.h>

#include <asm/idtentry.h>

#include <linux/kexec.h>

#include <linux/version.h>

#include <linux/vmalloc.h>

#include <linux/mm.h>
@@ -26,6 +27,8 @@ 
#include <linux/syscore_ops.h>

#include <clocksource/hyperv_timer.h>



int hyperv_init_cpuhp;



void *hv_hypercall_pg;

EXPORT_SYMBOL_GPL(hv_hypercall_pg);
@@ -401,6 +404,7 @@ void __init hyperv_init(void) 


	register_syscore_ops(&hv_syscore_ops);



	hyperv_init_cpuhp = cpuhp;

	return;



remove_cpuhp_state:

arch/x86/include/asm/mshyperv.h

+2 −0
Original line number Diff line number Diff line
@@ -74,6 +74,8 @@ static inline void hv_disable_stimer0_percpu_irq(int irq) {} 




#if IS_ENABLED(CONFIG_HYPERV)

extern int hyperv_init_cpuhp;



extern void *hv_hypercall_pg;

extern void  __percpu  **hyperv_pcpu_input_arg;

arch/x86/kernel/cpu/mshyperv.c

+18 −0
Original line number Diff line number Diff line
@@ -135,14 +135,32 @@ static void hv_machine_shutdown(void) 
{

	if (kexec_in_progress && hv_kexec_handler)

		hv_kexec_handler();



	/*

	 * Call hv_cpu_die() on all the CPUs, otherwise later the hypervisor

	 * corrupts the old VP Assist Pages and can crash the kexec kernel.

	 */

	if (kexec_in_progress && hyperv_init_cpuhp > 0)

		cpuhp_remove_state(hyperv_init_cpuhp);



	/* The function calls stop_other_cpus(). */

	native_machine_shutdown();



	/* Disable the hypercall page when there is only 1 active CPU. */

	if (kexec_in_progress)

		hyperv_cleanup();

}



static void hv_machine_crash_shutdown(struct pt_regs *regs)

{

	if (hv_crash_handler)

		hv_crash_handler(regs);



	/* The function calls crash_smp_send_stop(). */

	native_machine_crash_shutdown(regs);



	/* Disable the hypercall page when there is only 1 active CPU. */

	hyperv_cleanup();

}

#endif /* CONFIG_KEXEC_CORE */

#endif /* CONFIG_HYPERV */

drivers/hv/vmbus_drv.c

+0 −2
Original line number Diff line number Diff line
@@ -2550,7 +2550,6 @@ static void hv_kexec_handler(void) 
	/* Make sure conn_state is set as hv_synic_cleanup checks for it */

	mb();

	cpuhp_remove_state(hyperv_cpuhp_online);

	hyperv_cleanup();

};



static void hv_crash_handler(struct pt_regs *regs)
@@ -2566,7 +2565,6 @@ static void hv_crash_handler(struct pt_regs *regs) 
	cpu = smp_processor_id();

	hv_stimer_cleanup(cpu);

	hv_synic_disable_regs(cpu);

	hyperv_cleanup();

};



static int hv_synic_suspend(void)