linux-kernel - [PATCH v4 09/18] KVM: arm64: Allocate shared pKVM hyp stacktrace buffers

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Date:   Thu, 14 Jul 2022 23:10:18 -0700
From:   Kalesh Singh <kaleshsingh@...gle.com>
To:     maz@...nel.org, mark.rutland@....com, broonie@...nel.org,
        madvenka@...ux.microsoft.com
Cc:     will@...nel.org, qperret@...gle.com, tabba@...gle.com,
        kaleshsingh@...gle.com, james.morse@....com,
        alexandru.elisei@....com, suzuki.poulose@....com,
        catalin.marinas@....com, andreyknvl@...il.com,
        russell.king@...cle.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 v4 09/18] KVM: arm64: Allocate shared pKVM hyp stacktrace buffers

In protected nVHE mode the host cannot directly access
hypervisor memory, so we will dump the hypervisor stacktrace
to a shared buffer with the host.

The minimum size do the buffer required, assuming the min frame
size of [x29, x30] (2 * sizeof(long)), is half the combined size of
the hypervisor and overflow stacks plus an additional entry to
delimit the end of the stacktrace.

The stacktrace buffers are used later in the seried to dump the
nVHE hypervisor stacktrace when using protected-mode.

Signed-off-by: Kalesh Singh <kaleshsingh@...gle.com>
---
 arch/arm64/include/asm/memory.h      | 7 +++++++
 arch/arm64/kvm/hyp/nvhe/stacktrace.c | 4 ++++
 2 files changed, 11 insertions(+)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 0af70d9abede..28a4893d4b84 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -113,6 +113,13 @@
 
 #define OVERFLOW_STACK_SIZE	SZ_4K
 
+/*
+ * With the minimum frame size of [x29, x30], exactly half the combined
+ * sizes of the hyp and overflow stacks is needed to save the unwinded
+ * stacktrace; plus an additional entry to delimit the end.
+ */
+#define NVHE_STACKTRACE_SIZE	((OVERFLOW_STACK_SIZE + PAGE_SIZE) / 2 + sizeof(long))
+
 /*
  * Alignment of kernel segments (e.g. .text, .data).
  *
diff --git a/arch/arm64/kvm/hyp/nvhe/stacktrace.c b/arch/arm64/kvm/hyp/nvhe/stacktrace.c
index a3d5b34e1249..69e65b457f1c 100644
--- a/arch/arm64/kvm/hyp/nvhe/stacktrace.c
+++ b/arch/arm64/kvm/hyp/nvhe/stacktrace.c
@@ -9,3 +9,7 @@
 
 DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], overflow_stack)
 	__aligned(16);
+
+#ifdef CONFIG_PROTECTED_NVHE_STACKTRACE
+DEFINE_PER_CPU(unsigned long [NVHE_STACKTRACE_SIZE/sizeof(long)], pkvm_stacktrace);
+#endif /* CONFIG_PROTECTED_NVHE_STACKTRACE */
-- 
2.37.0.170.g444d1eabd0-goog