[PATCH 2/2] Drivers: hv: vmbus: Make pannic reporting to be more useful

[kys@exchange.microsoft.com]

From: "K. Y. Srinivasan" <kys@microsoft.com>

Hyper-V allows the guest to report panic and the guest can pass additional
information. All this is logged on the host. Currently Linux is passing back
information that is not particularly useful. Make the following changes:

1. Windows uses crash MSR P0 to report bugcheck code. Follow the same
convention for Linux as well.
2. It will be useful to know the gust ID of the Linux guest that has
paniced. Pass back this information.

These changes will help in better supporting Linux on Hyper-V

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 arch/x86/hyperv/hv_init.c       | 15 +++++++++------
 arch/x86/include/asm/mshyperv.h |  2 +-
 drivers/hv/vmbus_drv.c          |  4 ++--
 3 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index a5db63f728a2..aeb8edf32e2b 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -210,9 +210,10 @@ void hyperv_cleanup(void)
 }
 EXPORT_SYMBOL_GPL(hyperv_cleanup);
 
-void hyperv_report_panic(struct pt_regs *regs)
+void hyperv_report_panic(struct pt_regs *regs, long err)
 {
 	static bool panic_reported;
+	u64 guest_id;
 
 	/*
 	 * We prefer to report panic on 'die' chain as we have proper
@@ -223,11 +224,13 @@ void hyperv_report_panic(struct pt_regs *regs)
 		return;
 	panic_reported = true;
 
-	wrmsrl(HV_X64_MSR_CRASH_P0, regs->ip);
-	wrmsrl(HV_X64_MSR_CRASH_P1, regs->ax);
-	wrmsrl(HV_X64_MSR_CRASH_P2, regs->bx);
-	wrmsrl(HV_X64_MSR_CRASH_P3, regs->cx);
-	wrmsrl(HV_X64_MSR_CRASH_P4, regs->dx);
+	rdmsrl(HV_X64_MSR_GUEST_OS_ID, guest_id);
+
+	wrmsrl(HV_X64_MSR_CRASH_P0, err);
+	wrmsrl(HV_X64_MSR_CRASH_P1, guest_id);
+	wrmsrl(HV_X64_MSR_CRASH_P2, regs->ip);
+	wrmsrl(HV_X64_MSR_CRASH_P3, regs->ax);
+	wrmsrl(HV_X64_MSR_CRASH_P4, regs->sp);
 
 	/*
 	 * Let Hyper-V know there is crash data available
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 530f448fddaf..bd89104a5533 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -310,7 +310,7 @@ static inline int hv_cpu_number_to_vp_number(int cpu_number)
 void hyperv_init(void);
 void hyperv_setup_mmu_ops(void);
 void hyper_alloc_mmu(void);
-void hyperv_report_panic(struct pt_regs *regs);
+void hyperv_report_panic(struct pt_regs *regs, long err);
 bool hv_is_hypercall_page_setup(void);
 void hyperv_cleanup(void);
 #else /* CONFIG_HYPERV */
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index bca8188f3c8c..8fe13cd76acf 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -65,7 +65,7 @@ static int hyperv_panic_event(struct notifier_block *nb, unsigned long val,
 
 	regs = current_pt_regs();
 
-	hyperv_report_panic(regs);
+	hyperv_report_panic(regs, val);
 	return NOTIFY_DONE;
 }
 
@@ -75,7 +75,7 @@ static int hyperv_die_event(struct notifier_block *nb, unsigned long val,
 	struct die_args *die = (struct die_args *)args;
 	struct pt_regs *regs = die->regs;
 
-	hyperv_report_panic(regs);
+	hyperv_report_panic(regs, val);
 	return NOTIFY_DONE;
 }
 
-- 
2.14.1