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Subject[PATCH 4/4] x86/Hyper-V: Report crash register data or ksmg before running crash kernel
Date
From: Tianyu Lan <Tianyu.Lan@microsoft.com>

Hyper-V expects to get crash register data or kmsg via crash
enlightenment when guest crash happens. crash_kexec_post_notifiers
is default to be false and crash kernel runs before calling hv
panic callback and dumping kmsg. In this case, Hyper-V doesn't
get crash register data or kmsg from guest. Set crash_kexec_post
_notifiers to be true for Hyper-V VM and fix it.

Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
---
arch/x86/kernel/cpu/mshyperv.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index caa032ce3fe3..5e296a7e6036 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -263,6 +263,16 @@ static void __init ms_hyperv_init_platform(void)
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) {
--
2.14.5
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