arm64: hyperv: Add panic handler

Add a function to inform Hyper-V about a guest panic.

This code is built only when CONFIG_HYPERV is enabled.

Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Sunil Muthuswamy <sunilmut@microsoft.com>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/1628092359-61351-3-git-send-email-mikelley@microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>

diff --git a/arch/arm64/hyperv/hv_core.c b/arch/arm64/hyperv/hv_core.c
index 4c5dc0f..b54c347 100644 (file)
--- a/arch/arm64/hyperv/hv_core.c
+++ b/arch/arm64/hyperv/hv_core.c
@@ -127,3 +127,55 @@ u64 hv_get_vpreg(u32 msr)
        return output.as64.low;
 }
 EXPORT_SYMBOL_GPL(hv_get_vpreg);
+
+/*
+ * 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 hv_kmsg_dump() 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, the PC,
+        * and the SP.
+        */
+       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->sp);
+       hv_set_vpreg(HV_REGISTER_CRASH_P4, 0);
+
+       /*
+        * 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);