[PATCH 03/14] KVM: arm64: Add support for creating and checking a logging buffer inside hyp/nVHE

[George-Aurelian Popescu <georgepope@google.com>]

From: George Popescu <georgepope@google.com>

Share a buffer between the kernel and the hyp/nVHE code by using the
macros from kvm_debug_buffer.h.

The buffer is composed of a writing index and a statically allocated
array. The writing index counts how many elements have been written inside
the buffer and should be set to zero whenever the code goes back to
EL2 with the clear_kvm_debug_buffer macro.

To avoid consistency problems the buffer is defined per_cpu and is designed
to be read-only from the kernel perspective.

Check if there is any logging data from hyp/nVHE code.

Every time when the state returns back to the kernel after an hvc call,
the __kvm_arm_check_debug_buffer macro checks if there is any data inside
one of the predefined buffers.

Signed-off-by: George Popescu <georgepope@google.com>
---
 arch/arm64/include/asm/kvm_debug_buffer.h | 34 +++++++++++++++++++++++
 arch/arm64/include/asm/kvm_host.h         |  6 ++++
 arch/arm64/kvm/hyp/hyp-entry.S            |  2 +-
 3 files changed, 41 insertions(+), 1 deletion(-)
 create mode 100644 arch/arm64/include/asm/kvm_debug_buffer.h

diff --git a/arch/arm64/include/asm/kvm_debug_buffer.h b/arch/arm64/include/asm/kvm_debug_buffer.h
new file mode 100644
index 000000000000..30c9b0b1a7bf
--- /dev/null
+++ b/arch/arm64/include/asm/kvm_debug_buffer.h
@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright 2020 Google LLC
+ * Author: George Popescu <georgepope@google.com>
+ */
+#ifndef __ASSEMBLY__
+
+#include <linux/percpu-defs.h>
+#include <asm/kvm_asm.h>
+
+#ifdef __KVM_NVHE_HYPERVISOR__
+#define DEFINE_KVM_DEBUG_BUFFER(type_name, buff_name, size)             \
+	DEFINE_PER_CPU(type_name, buff_name)[(size)];	                \
+	DEFINE_PER_CPU(unsigned long, buff_name##_wr_ind) = 0
+
+#define DECLARE_KVM_DEBUG_BUFFER(type_name, buff_name, size)            \
+	DECLARE_PER_CPU(type_name, buff_name)[(size)];                  \
+	DECLARE_PER_CPU(unsigned long, buff_name##_wr_ind)
+
+#else
+
+#define DECLARE_KVM_DEBUG_BUFFER(type_name, buff_name, size)            \
+	DECLARE_PER_CPU(type_name, kvm_nvhe_sym(buff_name))[(size)];    \
+	DECLARE_PER_CPU(unsigned long, kvm_nvhe_sym(buff_name##_wr_ind))
+#endif //__KVM_NVHE_HYPERVISOR__
+
+#else
+
+.macro clear_kvm_debug_buffer sym tmp1, tmp2, tmp3
+	mov \tmp1, 0
+	hyp_str_this_cpu \sym, \tmp1, \tmp2, \tmp3
+.endm
+
+#endif // __ASSEMBLY__
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 905c2b87e05a..adc8957e9321 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -494,6 +494,10 @@ u64 __kvm_call_hyp(void *hypfn, ...);
 		__kvm_call_hyp(kvm_ksym_ref_nvhe(f), ##__VA_ARGS__);	\
 	})
 
+#define __kvm_arm_check_debug_buffer()					\
+{									\
+}
+
 /*
  * The couple of isb() below are there to guarantee the same behaviour
  * on VHE as on !VHE, where the eret to EL1 acts as a context
@@ -506,6 +510,7 @@ u64 __kvm_call_hyp(void *hypfn, ...);
 			isb();						\
 		} else {						\
 			kvm_call_hyp_nvhe(f, ##__VA_ARGS__);		\
+			__kvm_arm_check_debug_buffer();			\
 		}							\
 	} while(0)
 
@@ -518,6 +523,7 @@ u64 __kvm_call_hyp(void *hypfn, ...);
 			isb();						\
 		} else {						\
 			ret = kvm_call_hyp_nvhe_ret(f, ##__VA_ARGS__);	\
+			__kvm_arm_check_debug_buffer();			\
 		}							\
 									\
 		ret;							\
diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
index 46b4dab933d0..8df0082b9ccf 100644
--- a/arch/arm64/kvm/hyp/hyp-entry.S
+++ b/arch/arm64/kvm/hyp/hyp-entry.S
@@ -68,7 +68,7 @@ el1_sync:				// Guest trapped into EL2
 	cbnz	x1, el1_hvc_guest	// called HVC
 
 	/* Here, we're pretty sure the host called HVC. */
-	ldp	x0, x1, [sp], #16
+	ldp	x0, x1,	[sp], #16
 
 	/* Check for a stub HVC call */
 	cmp	x0, #HVC_STUB_HCALL_NR
-- 
2.28.0.618.gf4bc123cb7-goog