[PATCH 4.19 25/64] x86/Hyper-V: Report crash data in die() when panic_on_oops is set

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Tianyu Lan <Tianyu.Lan@microsoft.com>

[ Upstream commit f3a99e761efa616028b255b4de58e9b5b87c5545 ]

When oops happens with panic_on_oops unset, the oops
thread is killed by die() and system continues to run.
In such case, guest should not report crash register
data to host since system still runs. Check panic_on_oops
and return directly in hyperv_report_panic() when the function
is called in the die() and panic_on_oops is unset. Fix it.

Fixes: 7ed4325a44ea ("Drivers: hv: vmbus: Make panic reporting to be more useful")
Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20200406155331.2105-7-Tianyu.Lan@microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/hyperv/hv_init.c       | 6 +++++-
 arch/x86/include/asm/mshyperv.h | 2 +-
 drivers/hv/vmbus_drv.c          | 5 +++--
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 8a9cff1f129dc..1663ad84778ba 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -30,6 +30,7 @@
 #include <linux/clockchips.h>
 #include <linux/hyperv.h>
 #include <linux/slab.h>
+#include <linux/kernel.h>
 #include <linux/cpuhotplug.h>
 
 #ifdef CONFIG_HYPERV_TSCPAGE
@@ -427,11 +428,14 @@ void hyperv_cleanup(void)
 }
 EXPORT_SYMBOL_GPL(hyperv_cleanup);
 
-void hyperv_report_panic(struct pt_regs *regs, long err)
+void hyperv_report_panic(struct pt_regs *regs, long err, bool in_die)
 {
 	static bool panic_reported;
 	u64 guest_id;
 
+	if (in_die && !panic_on_oops)
+		return;
+
 	/*
 	 * We prefer to report panic on 'die' chain as we have proper
 	 * registers to report, but if we miss it (e.g. on BUG()) we need
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index f37704497d8f3..5b58a6cf487ff 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -338,7 +338,7 @@ static inline int cpumask_to_vpset(struct hv_vpset *vpset,
 
 void __init hyperv_init(void);
 void hyperv_setup_mmu_ops(void);
-void hyperv_report_panic(struct pt_regs *regs, long err);
+void hyperv_report_panic(struct pt_regs *regs, long err, bool in_die);
 void hyperv_report_panic_msg(phys_addr_t pa, size_t size);
 bool hv_is_hyperv_initialized(void);
 void hyperv_cleanup(void);
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index eacfe7933c4dd..fb22b72fd535a 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -43,6 +43,7 @@
 #include <linux/kdebug.h>
 #include <linux/efi.h>
 #include <linux/random.h>
+#include <linux/kernel.h>
 #include "hyperv_vmbus.h"
 
 struct vmbus_dynid {
@@ -85,7 +86,7 @@ static int hyperv_panic_event(struct notifier_block *nb, unsigned long val,
 	if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE
 	    && hyperv_report_reg()) {
 		regs = current_pt_regs();
-		hyperv_report_panic(regs, val);
+		hyperv_report_panic(regs, val, false);
 	}
 	return NOTIFY_DONE;
 }
@@ -102,7 +103,7 @@ static int hyperv_die_event(struct notifier_block *nb, unsigned long val,
 	 * the notification here.
 	 */
 	if (hyperv_report_reg())
-		hyperv_report_panic(regs, val);
+		hyperv_report_panic(regs, val, true);
 	return NOTIFY_DONE;
 }
 
-- 
2.20.1