[PATCH RESEND 05/10] Drivers: hv: vmbus: add special crash handler

K. Y. Srinivasan
2015-06-28T17:39:59Z

Full kernel hang is observed when kdump kernel starts after a crash. This
hang happens in vmbus_negotiate_version() function on
wait_for_completion() as Hyper-V host (Win2012R2 in my testing) never
responds to CHANNELMSG_INITIATE_CONTACT as it thinks the connection is
already established. We need to perform some mandatory minimalistic
cleanup before we start new kernel.

Reported-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
arch/x86/include/asm/mshyperv.h | 2 ++
arch/x86/kernel/cpu/mshyperv.c | 22 ++++++++++++++++++++++
drivers/hv/vmbus_drv.c | 14 ++++++++++++++
3 files changed, 38 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index d3db910..d02f9c9 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -22,4 +22,6 @@ void hv_remove_vmbus_irq(void);

void hv_setup_kexec_handler(void (*handler)(void));
void hv_remove_kexec_handler(void);
+void hv_setup_crash_handler(void (*handler)(struct pt_regs *regs));
+void hv_remove_crash_handler(void);
#endif
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 09911aa..1a6e742 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -35,6 +35,7 @@ struct ms_hyperv_info ms_hyperv;
EXPORT_SYMBOL_GPL(ms_hyperv);

static void (*hv_kexec_handler)(void);
+static void (*hv_crash_handler)(struct pt_regs *regs);

#if IS_ENABLED(CONFIG_HYPERV)
static void (*vmbus_handler)(void);
@@ -85,6 +86,18 @@ void hv_remove_kexec_handler(void)
hv_kexec_handler = NULL;
}
EXPORT_SYMBOL_GPL(hv_remove_kexec_handler);
+
+void hv_setup_crash_handler(void (*handler)(struct pt_regs *regs))
+{
+ hv_crash_handler = handler;
+}
+EXPORT_SYMBOL_GPL(hv_setup_crash_handler);
+
+void hv_remove_crash_handler(void)
+{
+ hv_crash_handler = NULL;
+}
+EXPORT_SYMBOL_GPL(hv_remove_crash_handler);
#endif

static void hv_machine_shutdown(void)
@@ -94,6 +107,14 @@ static void hv_machine_shutdown(void)
native_machine_shutdown();
}

+static void hv_machine_crash_shutdown(struct pt_regs *regs)
+{
+ if (hv_crash_handler)
+ hv_crash_handler(regs);
+ native_machine_crash_shutdown(regs);
+}
+
+
static uint32_t __init ms_hyperv_platform(void)
{
u32 eax;
@@ -167,6 +188,7 @@ static void __init ms_hyperv_init_platform(void)
#endif

machine_ops.shutdown = hv_machine_shutdown;
+ machine_ops.crash_shutdown = hv_machine_crash_shutdown;
}

const __refconst struct hypervisor_x86 x86_hyper_ms_hyperv = {
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 31748a2..1ed9b32 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1071,6 +1071,18 @@ static void hv_kexec_handler(void)
hv_cleanup();
};

+static void hv_crash_handler(struct pt_regs *regs)
+{
+ vmbus_initiate_unload();
+ /*
+ * In crash handler we can't schedule synic cleanup for all CPUs,
+ * doing the cleanup for current CPU only. This should be sufficient
+ * for kdump.
+ */
+ hv_synic_cleanup(NULL);
+ hv_cleanup();
+};
+
static int __init hv_acpi_init(void)
{
int ret, t;
@@ -1104,6 +1116,7 @@ static int __init hv_acpi_init(void)
goto cleanup;

hv_setup_kexec_handler(hv_kexec_handler);
+ hv_setup_crash_handler(hv_crash_handler);

return 0;

@@ -1118,6 +1131,7 @@ static void __exit vmbus_exit(void)
int cpu;

hv_remove_kexec_handler();
+ hv_remove_crash_handler();
vmbus_connection.conn_state = DISCONNECTED;
hv_synic_clockevents_cleanup();
vmbus_disconnect();
--
1.7.4.1