From: Anirudh Rayabharam (Microsoft) anirudh@anirudhrb.com
9636be85cc5b ("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 dfe94d4086e4 ("x86/hyperv: Fix kexec panic/hang issues").
Set hyperv_init_cpuhp to CPUHP_AP_HYPERV_ONLINE upon successful setup so that the hyperv cpuhp state is removed correctly on kexec and the necessary cleanup takes place.
Cc: stable@vger.kernel.org Fixes: 9636be85cc5b ("x86/hyperv: Fix hyperv_pcpu_input_arg handling when CPUs go online/offline") Signed-off-by: Anirudh Rayabharam (Microsoft) anirudh@anirudhrb.com --- arch/x86/hyperv/hv_init.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c index 17a71e92a343..81d1981a75d1 100644 --- a/arch/x86/hyperv/hv_init.c +++ b/arch/x86/hyperv/hv_init.c @@ -607,7 +607,7 @@ void __init hyperv_init(void)
register_syscore_ops(&hv_syscore_ops);
- hyperv_init_cpuhp = cpuhp; + hyperv_init_cpuhp = CPUHP_AP_HYPERV_ONLINE;
if (cpuid_ebx(HYPERV_CPUID_FEATURES) & HV_ACCESS_PARTITION_ID) hv_get_partition_id(); @@ -637,7 +637,7 @@ 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: