[PATCH v4 18/18] KVM: arm64: Dump nVHE hypervisor stack on panic

[Kalesh Singh <kaleshsingh@google.com>]

On hyp_panic(), unwind and dump the nVHE hypervisor stack trace.
In protected nVHE mode, hypervisor stacktraces are only produced
if CONFIG_PROTECTED_NVHE_STACKTRACE is enabled.

Example backtrace:

[  126.862960] kvm [371]: nVHE hyp panic at: [<ffff8000090a51d0>] __kvm_nvhe_recursive_death+0x10/0x34!
[  126.869920] kvm [371]: Protected nVHE HYP call trace:
[  126.870528] kvm [371]:  [<ffff8000090a5570>] __kvm_nvhe_hyp_panic+0xac/0xf8
[  126.871342] kvm [371]:  [<ffff8000090a55cc>] __kvm_nvhe_hyp_panic_bad_stack+0x10/0x10
[  126.872174] kvm [371]:  [<ffff8000090a51e4>] __kvm_nvhe_recursive_death+0x24/0x34
[  126.872971] kvm [371]:  [<ffff8000090a51e4>] __kvm_nvhe_recursive_death+0x24/0x34
. . .
[  126.927314] kvm [371]:  [<ffff8000090a51e4>] __kvm_nvhe_recursive_death+0x24/0x34
[  126.927727] kvm [371]:  [<ffff8000090a51e4>] __kvm_nvhe_recursive_death+0x24/0x34
[  126.928137] kvm [371]:  [<ffff8000090a4de4>] __kvm_nvhe___kvm_vcpu_run+0x30/0x40c
[  126.928561] kvm [371]:  [<ffff8000090a7b64>] __kvm_nvhe_handle___kvm_vcpu_run+0x30/0x48
[  126.928984] kvm [371]:  [<ffff8000090a78b8>] __kvm_nvhe_handle_trap+0xc4/0x128
[  126.929385] kvm [371]:  [<ffff8000090a6864>] __kvm_nvhe___host_exit+0x64/0x64
[  126.929804] kvm [371]: ---- End of Protected nVHE HYP call trace ----

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
---
 arch/arm64/kvm/handle_exit.c     | 4 ++++
 arch/arm64/kvm/hyp/nvhe/switch.c | 5 +++++
 2 files changed, 9 insertions(+)

diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index f66c0142b335..ef8b57953aa2 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -17,6 +17,7 @@
 #include <asm/kvm_emulate.h>
 #include <asm/kvm_mmu.h>
 #include <asm/debug-monitors.h>
+#include <asm/stacktrace/nvhe.h>
 #include <asm/traps.h>
 
 #include <kvm/arm_hypercalls.h>
@@ -353,6 +354,9 @@ void __noreturn __cold nvhe_hyp_panic_handler(u64 esr, u64 spsr,
 				(void *)panic_addr);
 	}
 
+	/* Dump the nVHE hypervisor backtrace */
+	kvm_nvhe_dump_backtrace(hyp_offset);
+
 	/*
 	 * Hyp has panicked and we're going to handle that by panicking the
 	 * kernel. The kernel offset will be revealed in the panic so we're
diff --git a/arch/arm64/kvm/hyp/nvhe/switch.c b/arch/arm64/kvm/hyp/nvhe/switch.c
index 6db801db8f27..a50cfd39dedb 100644
--- a/arch/arm64/kvm/hyp/nvhe/switch.c
+++ b/arch/arm64/kvm/hyp/nvhe/switch.c
@@ -25,6 +25,7 @@
 #include <asm/fpsimd.h>
 #include <asm/debug-monitors.h>
 #include <asm/processor.h>
+#include <asm/stacktrace/nvhe.h>
 
 #include <nvhe/fixed_config.h>
 #include <nvhe/mem_protect.h>
@@ -375,6 +376,10 @@ asmlinkage void __noreturn hyp_panic(void)
 		__sysreg_restore_state_nvhe(host_ctxt);
 	}
 
+	/* Prepare to dump kvm nvhe hyp stacktrace */
+	kvm_nvhe_prepare_backtrace((unsigned long)__builtin_frame_address(0),
+				   _THIS_IP_);
+
 	__hyp_do_panic(host_ctxt, spsr, elr, par);
 	unreachable();
 }
-- 
2.37.0.170.g444d1eabd0-goog