This is a note to let you know that I've just added the patch titled x86/Hyper-V: Report crash register data or kmsg before running crash kernel to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: x86-hyper-v-report-crash-register-data-or-kmsg-before-running-crash-kernel.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From a11589563e96bf262767294b89b25a9d44e7303b Mon Sep 17 00:00:00 2001 From: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx> Date: Mon, 6 Apr 2020 08:53:29 -0700 Subject: x86/Hyper-V: Report crash register data or kmsg before running crash kernel From: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx> commit a11589563e96bf262767294b89b25a9d44e7303b upstream. We want to notify Hyper-V when a Linux guest VM crash occurs, so there is a record of the crash even when kdump is enabled. But crash_kexec_post_notifiers defaults to "false", so the kdump kernel runs before the notifiers and Hyper-V never gets notified. Fix this by always setting crash_kexec_post_notifiers to be true for Hyper-V VMs. Fixes: 81b18bce48af ("Drivers: HV: Send one page worth of kmsg dump over Hyper-V during panic") Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx> Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20200406155331.2105-5-Tianyu.Lan@xxxxxxxxxxxxx Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/kernel/cpu/mshyperv.c | 10 ++++++++++ 1 file changed, 10 insertions(+) --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -263,6 +263,16 @@ static void __init ms_hyperv_init_platfo cpuid_eax(HYPERV_CPUID_NESTED_FEATURES); } + /* + * Hyper-V expects to get crash register data or kmsg when + * crash enlightment is available and system crashes. Set + * crash_kexec_post_notifiers to be true to make sure that + * calling crash enlightment interface before running kdump + * kernel. + */ + if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) + crash_kexec_post_notifiers = true; + #ifdef CONFIG_X86_LOCAL_APIC if (ms_hyperv.features & HV_X64_ACCESS_FREQUENCY_MSRS && ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE) { Patches currently in stable-queue which might be from Tianyu.Lan@xxxxxxxxxxxxx are queue-5.4/x86-hyper-v-unload-vmbus-channel-in-hv-panic-callback.patch queue-5.4/x86-hyper-v-trigger-crash-enlightenment-only-once-during-system-crash.patch queue-5.4/x86-hyper-v-report-crash-register-data-or-kmsg-before-running-crash-kernel.patch queue-5.4/x86-hyper-v-report-crash-register-data-when-sysctl_record_panic_msg-is-not-set.patch queue-5.4/x86-hyper-v-report-crash-data-in-die-when-panic_on_oops-is-set.patch