[PATCH 04/14] KVM: arm64: Add support for buffer usage

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

From: George Popescu <georgepope@google.com>

Use init_kvm_debug_buffer macro to init a pointer to the kvm_debug_buffer
and a pointer to the write_index. It is needed a hyp/nVHE version and a
kernel version because there are required different functions to extract
the per_cpu data.

Iterate through the buffer using the for_each_kvm_debug_buffer_slot. The
parameters are the buffer's name, the buffer's type, a pointer of
the type of the buffer, which is used to iterate through it,
an (unsigned long *) to compute the write index and an
unsigned long iterator.

Get the buffer's next empty slot using the kvm_debug_buffer_next_slot function,
the required parameters are a pointer to the buffer start, a pointer to
the writing index, the stored type size and the allocated size of the
buffer. This function has a meaning only inside hyp/nVHE, because it
shouldn't be possible to write inside the buffer from the kernel.

Signed-off-by: George Popescu <georgepope@google.com>
---
 arch/arm64/include/asm/kvm_debug_buffer.h | 31 +++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_debug_buffer.h b/arch/arm64/include/asm/kvm_debug_buffer.h
index 30c9b0b1a7bf..e451c11a77a7 100644
--- a/arch/arm64/include/asm/kvm_debug_buffer.h
+++ b/arch/arm64/include/asm/kvm_debug_buffer.h
@@ -17,10 +17,37 @@
 	DECLARE_PER_CPU(type_name, buff_name)[(size)];                  \
 	DECLARE_PER_CPU(unsigned long, buff_name##_wr_ind)
 
+static inline void *kvm_debug_buffer_next_slot(void *buff, unsigned long *buff_ind,
+			unsigned int struct_size, unsigned long buff_size)
+{
+	void *res = NULL;
+
+	if (*buff_ind < buff_size) {
+		res = buff + (*buff_ind * struct_size);
+		*buff_ind = *buff_ind + 1;
+	}
+	return res;
+}
+
+#define init_kvm_debug_buffer(buff_name, buff_type, buff_pointer, write_ind)		\
+	do {										\
+		buff = (buff_type *) __hyp_this_cpu_ptr(buff_name);			\
+		buff_ind = (unsigned long *) __hyp_this_cpu_ptr(buff_name##_wr_ind);	\
+	} while (0)
+
 #else
 
-#define DECLARE_KVM_DEBUG_BUFFER(type_name, buff_name, size)            \
-	DECLARE_PER_CPU(type_name, kvm_nvhe_sym(buff_name))[(size)];    \
+#define init_kvm_debug_buffer(buff_name, buff_type, buff_pointer, write_ind)		\
+	do {										\
+		buff_pointer = (buff_type *) this_cpu_ptr_nvhe(buff_name);		\
+		write_ind = (unsigned long *) this_cpu_ptr_nvhe(buff_name##_wr_ind);	\
+	} while (0)
+
+#define for_each_kvm_debug_buffer_slot(slot, write_ind, it)				\
+	for ((it) = 0; (it) < *(write_ind); ++(it), ++(slot))
+
+#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__
 
-- 
2.28.0.618.gf4bc123cb7-goog