arm64: hyperv: Add kexec and panic handlers

Add functions to set up and remove kexec and panic
handlers, and to inform Hyper-V about a guest panic.
These functions are called from architecture independent
code in the VMbus driver.

This code is built only when CONFIG_HYPERV is enabled.

Signed-off-by: Michael Kelley <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>

Author: kelleymh

arch/arm64/hyperv/hv_core.c

@@ -211,3 +211,83 @@ void hv_get_vpreg_128(u32 msr, struct hv_get_vp_registers_output *res)
 	kfree(output);
 }
 EXPORT_SYMBOL_GPL(hv_get_vpreg_128);
+
+
+/*
+ * hyperv_report_panic - report a panic to Hyper-V.  This function uses
+ * the older version of the Hyper-V interface that admittedly doesn't
+ * pass enough information to be useful beyond just recording the
+ * occurrence of a panic. The parallel hyperv_report_panic_msg() uses the
+ * new interface that allows reporting 4 Kbytes of data, which is much
+ * more useful. Hyper-V on ARM64 always supports the newer interface, but
+ * we retain support for the older version because the sysadmin is allowed
+ * to disable the newer version via sysctl in case of information security
+ * concerns about the more verbose version.
+ */
+void hyperv_report_panic(struct pt_regs *regs, long err, bool in_die)
+{
+	static bool panic_reported;
+	u64 guest_id;
+
+	/* Don't report a panic to Hyper-V if we're not going to panic */
+	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
+	 * to report it on 'panic'.
+	 *
+	 * Calling code in the 'die' and 'panic' paths ensures that only
+	 * one CPU is running this code, so no atomicity is needed.
+	 */
+	if (panic_reported)
+		return;
+	panic_reported = true;
+
+	guest_id = hv_get_vpreg(HV_REGISTER_GUEST_OSID);
+
+	/*
+	 * Hyper-V provides the ability to store only 5 values.
+	 * Pick the passed in error value, the guest_id, and the PC.
+	 * The first two general registers are added arbitrarily.
+	 */
+	hv_set_vpreg(HV_REGISTER_CRASH_P0, err);
+	hv_set_vpreg(HV_REGISTER_CRASH_P1, guest_id);
+	hv_set_vpreg(HV_REGISTER_CRASH_P2, regs->pc);
+	hv_set_vpreg(HV_REGISTER_CRASH_P3, regs->regs[0]);
+	hv_set_vpreg(HV_REGISTER_CRASH_P4, regs->regs[1]);
+
+	/*
+	 * Let Hyper-V know there is crash data available
+	 */
+	hv_set_vpreg(HV_REGISTER_CRASH_CTL, HV_CRASH_CTL_CRASH_NOTIFY);
+}
+EXPORT_SYMBOL_GPL(hyperv_report_panic);
+
+/*
+ * hyperv_report_panic_msg - report panic message to Hyper-V
+ * @pa: physical address of the panic page containing the message
+ * @size: size of the message in the page
+ */
+void hyperv_report_panic_msg(phys_addr_t pa, size_t size)
+{
+	/*
+	 * P3 to contain the physical address of the panic page & P4 to
+	 * contain the size of the panic data in that page. Rest of the
+	 * registers are no-op when the NOTIFY_MSG flag is set.
+	 */
+	hv_set_vpreg(HV_REGISTER_CRASH_P0, 0);
+	hv_set_vpreg(HV_REGISTER_CRASH_P1, 0);
+	hv_set_vpreg(HV_REGISTER_CRASH_P2, 0);
+	hv_set_vpreg(HV_REGISTER_CRASH_P3, pa);
+	hv_set_vpreg(HV_REGISTER_CRASH_P4, size);
+
+	/*
+	 * Let Hyper-V know there is crash data available along with
+	 * the panic message.
+	 */
+	hv_set_vpreg(HV_REGISTER_CRASH_CTL,
+	       (HV_CRASH_CTL_CRASH_NOTIFY | HV_CRASH_CTL_CRASH_NOTIFY_MSG));
+}
+EXPORT_SYMBOL_GPL(hyperv_report_panic_msg);

arch/arm64/hyperv/mshyperv.c

@@ -23,6 +23,8 @@
 
 static void (*vmbus_handler)(void);
 static void (*hv_stimer0_handler)(void);
+static void (*hv_kexec_handler)(void);
+static void (*hv_crash_handler)(struct pt_regs *regs);
 
 static int vmbus_irq;
 static long __percpu *vmbus_evt;
@@ -131,3 +133,27 @@ void hv_remove_stimer0_irq(int irq)
 	}
 }
 EXPORT_SYMBOL_GPL(hv_remove_stimer0_irq);
+
+void hv_setup_kexec_handler(void (*handler)(void))
+{
+	hv_kexec_handler = handler;
+}
+EXPORT_SYMBOL_GPL(hv_setup_kexec_handler);
+
+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);

arch/arm64/include/asm/mshyperv.h

@@ -149,6 +149,8 @@ static inline int hv_get_vector(void)
 	return vmbus_interrupt;
 }
 
+#define hv_get_crash_ctl(val) \
+		(val = hv_get_vpreg(HV_REGISTER_CRASH_CTL))
 
 /* SMCCC hypercall parameters */
 #define HV_SMCCC_FUNC_NUMBER	1