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Date:   Thu, 14 Jul 2022 23:10:20 -0700
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Subject: [PATCH v4 11/18] KVM: arm64: Stub implementation of non-protected
 nVHE HYP stack unwinder
From:   Kalesh Singh <kaleshsingh@google.com>
To:     maz@kernel.org, mark.rutland@arm.com, broonie@kernel.org,
        madvenka@linux.microsoft.com
Cc:     will@kernel.org, qperret@google.com, tabba@google.com,
        kaleshsingh@google.com, james.morse@arm.com,
        alexandru.elisei@arm.com, suzuki.poulose@arm.com,
        catalin.marinas@arm.com, andreyknvl@gmail.com,
        russell.king@oracle.com, vincenzo.frascino@arm.com,
        mhiramat@kernel.org, ast@kernel.org, drjones@redhat.com,
        wangkefeng.wang@huawei.com, elver@google.com, keirf@google.com,
        yuzenghui@huawei.com, ardb@kernel.org, oupton@google.com,
        linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu,
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Precedence: bulk

Add stub implementations of non-protected nVHE stack unwinder, for
building. These are implemented later in this series.

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
---
 arch/arm64/include/asm/stacktrace/nvhe.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/arch/arm64/include/asm/stacktrace/nvhe.h b/arch/arm64/include/asm/stacktrace/nvhe.h
index 1eac4e57f2ae..36cf7858ddd8 100644
--- a/arch/arm64/include/asm/stacktrace/nvhe.h
+++ b/arch/arm64/include/asm/stacktrace/nvhe.h
@@ -8,6 +8,12 @@
  *      the HYP memory. The stack is unwinded in EL2 and dumped to a shared
  *      buffer where the host can read and print the stacktrace.
  *
+ *   2) Non-protected nVHE mode - the host can directly access the
+ *      HYP stack pages and unwind the HYP stack in EL1. This saves having
+ *      to allocate shared buffers for the host to read the unwinded
+ *      stacktrace.
+ *
+ *
  * Copyright (C) 2022 Google LLC
  */
 #ifndef __ASM_STACKTRACE_NVHE_H
@@ -53,5 +59,21 @@ static int notrace unwind_next(struct unwind_state *state)
 NOKPROBE_SYMBOL(unwind_next);
 #endif	/* CONFIG_PROTECTED_NVHE_STACKTRACE */
 
+/*
+ * Non-protected nVHE HYP stack unwinder
+ */
+#else	/* !__KVM_NVHE_HYPERVISOR__ */
+static inline bool on_overflow_stack(unsigned long sp, unsigned long size,
+				     struct stack_info *info)
+{
+	return false;
+}
+
+static int notrace unwind_next(struct unwind_state *state)
+{
+	return 0;
+}
+NOKPROBE_SYMBOL(unwind_next);
+
 #endif	/* __KVM_NVHE_HYPERVISOR__ */
 #endif	/* __ASM_STACKTRACE_NVHE_H */
-- 
2.37.0.170.g444d1eabd0-goog