linux-kernel - [PATCH v5 11/17] KVM: arm64: Stub implementation of non-protected nVHE HYP stack unwinder

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Date:   Wed, 20 Jul 2022 22:57:22 -0700
From:   Kalesh Singh <kaleshsingh@...gle.com>
To:     maz@...nel.org, mark.rutland@....com, broonie@...nel.org,
        madvenka@...ux.microsoft.com, tabba@...gle.com
Cc:     will@...nel.org, qperret@...gle.com, kaleshsingh@...gle.com,
        james.morse@....com, alexandru.elisei@....com,
        suzuki.poulose@....com, catalin.marinas@....com,
        andreyknvl@...il.com, vincenzo.frascino@....com,
        mhiramat@...nel.org, ast@...nel.org, drjones@...hat.com,
        wangkefeng.wang@...wei.com, elver@...gle.com, keirf@...gle.com,
        yuzenghui@...wei.com, ardb@...nel.org, oupton@...gle.com,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org, android-mm@...gle.com,
        kernel-team@...roid.com
Subject: [PATCH v5 11/17] KVM: arm64: Stub implementation of non-protected
 nVHE HYP stack unwinder

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

Signed-off-by: Kalesh Singh <kaleshsingh@...gle.com>
---

Changes in v5:
  - Mark unwind_next() as inline, per Marc
  - Comment !__KVM_NVHE_HYPERVISOR__ unwinder path, per Marc

 arch/arm64/include/asm/stacktrace/nvhe.h | 26 ++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/arch/arm64/include/asm/stacktrace/nvhe.h b/arch/arm64/include/asm/stacktrace/nvhe.h
index 80d71932afff..3078501f8e22 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
@@ -55,5 +61,25 @@ static inline int notrace unwind_next(struct unwind_state *state)
 NOKPROBE_SYMBOL(unwind_next);
 #endif	/* CONFIG_PROTECTED_NVHE_STACKTRACE */
 
+#else	/* !__KVM_NVHE_HYPERVISOR__ */
+/*
+ * Conventional (non-protected) nVHE HYP stack unwinder
+ *
+ * In non-protected mode, the unwinding is done from kernel proper context
+ * (by the host in EL1).
+ */
+
+static inline bool on_overflow_stack(unsigned long sp, unsigned long size,
+				     struct stack_info *info)
+{
+	return false;
+}
+
+static inline 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