x86/Hyper-V: Report crash register data or kmsg before running crash kernel

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@microsoft.com>
Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
Link: https://lore.kernel.org/r/20200406155331.2105-5-Tianyu.Lan@microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 53706fb564337c3fe5ed78437120b5535024f4dd..ebf34c7bc8bc0dfcb0cac217d522358c8c192b04 100644 (file)
--- 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) {