Commit a4a68b08 authored by Anirudh Rayabharam (Microsoft)'s avatar Anirudh Rayabharam (Microsoft) Committed by Wen Zhiwei
Browse files

x86/hyperv: fix kexec crash due to VP assist page corruption 

stable inclusion
from stable-v6.6.52
commit 2ae1beb3ab4f28868cc5d1541d05e1fbee3ad825
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IAYXOD

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2ae1beb3ab4f28868cc5d1541d05e1fbee3ad825



--------------------------------

commit b9af6418279c4cf73ca073f8ea024992b38be8ab upstream.

commit 9636be85 ("x86/hyperv: Fix hyperv_pcpu_input_arg handling when
CPUs go online/offline") introduces a new cpuhp state for hyperv
initialization.

cpuhp_setup_state() returns the state number if state is
CPUHP_AP_ONLINE_DYN or CPUHP_BP_PREPARE_DYN and 0 for all other states.
For the hyperv case, since a new cpuhp state was introduced it would
return 0. However, in hv_machine_shutdown(), the cpuhp_remove_state() call
is conditioned upon "hyperv_init_cpuhp > 0". This will never be true and
so hv_cpu_die() won't be called on all CPUs. This means the VP assist page
won't be reset. When the kexec kernel tries to setup the VP assist page
again, the hypervisor corrupts the memory region of the old VP assist page
causing a panic in case the kexec kernel is using that memory elsewhere.
This was originally fixed in commit dfe94d40 ("x86/hyperv: Fix kexec
panic/hang issues").

Get rid of hyperv_init_cpuhp entirely since we are no longer using a
dynamic cpuhp state and use CPUHP_AP_HYPERV_ONLINE directly with
cpuhp_remove_state().

Cc: stable@vger.kernel.org
Fixes: 9636be85 ("x86/hyperv: Fix hyperv_pcpu_input_arg handling when CPUs go online/offline")
Signed-off-by: default avatarAnirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
Reviewed-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: default avatarMichael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/20240828112158.3538342-1-anirudh@anirudhrb.com


Signed-off-by: default avatarWei Liu <wei.liu@kernel.org>
Message-ID: <20240828112158.3538342-1-anirudh@anirudhrb.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarWen Zhiwei <wenzhiwei@kylinos.cn>
parent 0218354c

arch/x86/hyperv/hv_init.c

+1 −4
Original line number Diff line number Diff line
@@ -35,7 +35,6 @@ 
#include <clocksource/hyperv_timer.h>

#include <linux/highmem.h>



int hyperv_init_cpuhp;

u64 hv_current_partition_id = ~0ull;

EXPORT_SYMBOL_GPL(hv_current_partition_id);
@@ -607,8 +606,6 @@ void __init hyperv_init(void) 


	register_syscore_ops(&hv_syscore_ops);



	hyperv_init_cpuhp = cpuhp;



	if (cpuid_ebx(HYPERV_CPUID_FEATURES) & HV_ACCESS_PARTITION_ID)

		hv_get_partition_id();
@@ -637,7 +634,7 @@ void __init hyperv_init(void) 
clean_guest_os_id:

	wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);

	hv_ivm_msr_write(HV_X64_MSR_GUEST_OS_ID, 0);

	cpuhp_remove_state(cpuhp);

	cpuhp_remove_state(CPUHP_AP_HYPERV_ONLINE);

free_ghcb_page:

	free_percpu(hv_ghcb_pg);

free_vp_assist_page:

arch/x86/include/asm/mshyperv.h

+0 −1
Original line number Diff line number Diff line
@@ -40,7 +40,6 @@ static inline unsigned char hv_get_nmi_reason(void) 
}



#if IS_ENABLED(CONFIG_HYPERV)

extern int hyperv_init_cpuhp;

extern bool hyperv_paravisor_present;



extern void *hv_hypercall_pg;

arch/x86/kernel/cpu/mshyperv.c

+2 −2
Original line number Diff line number Diff line
@@ -199,8 +199,8 @@ static void hv_machine_shutdown(void) 
	 * 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);

	if (kexec_in_progress)

		cpuhp_remove_state(CPUHP_AP_HYPERV_ONLINE);



	/* The function calls stop_other_cpus(). */

	native_machine_shutdown();