[PATCH v3 6/9] xen/riscv: introduce functionality to work with cpu info

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

struct pcpu_info is introduced to store pcpu related information.
At the moment, it is only processor_id but in the fututre it will be
guest cpu information and some temporary variables which will be
used during save/restore of vcpu registers.

set_processor_id() and get_processor_id() are introduced to set and
get processor id which is stored in pcpu_info.

__cpuid_to_hartid_map[NR_CPUS] is introduced to store the mapping
between Xen logical CPU and hartid ( physical CPU id ) and auxiliary
macros cpuid_to_hartid_map() for convience access to __cpuid_to_hartid_map[].

smp_processor_id() is defined properly as it is enough to information to
define it now instead of seting it to "dummy" 0.

Also, tp registers is initialized to point to pcpu_info[0];
set_processor_id is set to 0 as Xen is running on logical cpu 0 and
save physical CPU id for current logical CPU id in __cpuid_to_hartid_map[].

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
Changes in V3:
 - new patch.
---
 xen/arch/riscv/Makefile                |  2 ++
 xen/arch/riscv/include/asm/processor.h | 35 ++++++++++++++++++++++++--
 xen/arch/riscv/include/asm/smp.h       | 10 ++++++++
 xen/arch/riscv/setup.c                 | 13 ++++++++++
 xen/arch/riscv/smp.c                   |  4 +++
 xen/arch/riscv/smpboot.c               | 12 +++++++++
 6 files changed, 74 insertions(+), 2 deletions(-)
 create mode 100644 xen/arch/riscv/smp.c
 create mode 100644 xen/arch/riscv/smpboot.c

diff --git a/xen/arch/riscv/Makefile b/xen/arch/riscv/Makefile
index 81b77b13d6..334fd24547 100644
--- a/xen/arch/riscv/Makefile
+++ b/xen/arch/riscv/Makefile
@@ -4,6 +4,8 @@ obj-y += mm.o
 obj-$(CONFIG_RISCV_64) += riscv64/
 obj-y += sbi.o
 obj-y += setup.o
+obj-y += smp.o
+obj-y += smpboot.o
 obj-y += stubs.o
 obj-y += traps.o
 obj-y += vm_event.o
diff --git a/xen/arch/riscv/include/asm/processor.h 
b/xen/arch/riscv/include/asm/processor.h
index 3ae164c265..4c3e45fd17 100644
--- a/xen/arch/riscv/include/asm/processor.h
+++ b/xen/arch/riscv/include/asm/processor.h
@@ -12,8 +12,39 @@
 
 #ifndef __ASSEMBLY__
 
-/* TODO: need to be implemeted */
-#define smp_processor_id() 0
+#include <xen/bug.h>
+#include <xen/types.h>
+
+register struct pcpu_info *tp asm ("tp");
+
+struct pcpu_info {
+    unsigned int processor_id;
+};
+
+/* tp points to one of these */
+extern struct pcpu_info pcpu_info[NR_CPUS];
+
+#define get_processor_id()      (tp->processor_id)
+#define set_processor_id(id)    do { \
+    tp->processor_id = id;           \
+} while(0)
+
+static inline unsigned int smp_processor_id(void)
+{
+    unsigned int id;
+
+    id = get_processor_id();
+
+    /*
+     * Technically the hartid can be greater than what a uint can hold.
+     * If such a system were to exist, we will need to change
+     * the smp_processor_id() API to be unsigned long instead of
+     * unsigned int.
+     */
+    BUG_ON(id > UINT_MAX);
+
+    return id;
+}
 
 /* On stack VCPU state */
 struct cpu_user_regs
diff --git a/xen/arch/riscv/include/asm/smp.h b/xen/arch/riscv/include/asm/smp.h
index b1ea91b1eb..3fff27a8a5 100644
--- a/xen/arch/riscv/include/asm/smp.h
+++ b/xen/arch/riscv/include/asm/smp.h
@@ -5,6 +5,8 @@
 #include <xen/cpumask.h>
 #include <xen/percpu.h>
 
+#define INVALID_HARTID UINT_MAX
+
 DECLARE_PER_CPU(cpumask_var_t, cpu_sibling_mask);
 DECLARE_PER_CPU(cpumask_var_t, cpu_core_mask);
 
@@ -14,6 +16,14 @@ DECLARE_PER_CPU(cpumask_var_t, cpu_core_mask);
  */
 #define park_offline_cpus false
 
+void smp_setup_processor_id(unsigned long boot_cpu_hartid);
+
+/*
+ * Mapping between linux logical cpu index and hartid.
+ */
+extern unsigned long __cpuid_to_hartid_map[NR_CPUS];
+#define cpuid_to_hartid_map(cpu) __cpuid_to_hartid_map[cpu]
+
 #endif
 
 /*
diff --git a/xen/arch/riscv/setup.c b/xen/arch/riscv/setup.c
index 13f0e8c77d..37b234360c 100644
--- a/xen/arch/riscv/setup.c
+++ b/xen/arch/riscv/setup.c
@@ -40,6 +40,19 @@ void __init noreturn start_xen(unsigned long bootcpu_id,
 {
     remove_identity_mapping();
 
+    /*
+     * tp register contains an address of physical cpu information.
+     * So write physical CPU info of boot cpu to tp register
+     * It will be used later by get_processor_id() to get process_id ( look at
+     * <asm/processor.h> ):
+     *   #define get_processor_id()    (tp->processor_id)
+     */
+    asm volatile ("mv tp, %0" : : "r"((unsigned long)&pcpu_info[0]));
+
+    set_processor_id(0);
+
+    smp_setup_processor_id(bootcpu_id);
+
     trap_init();
 
 #ifdef CONFIG_SELF_TESTS
diff --git a/xen/arch/riscv/smp.c b/xen/arch/riscv/smp.c
new file mode 100644
index 0000000000..006a062ad7
--- /dev/null
+++ b/xen/arch/riscv/smp.c
@@ -0,0 +1,4 @@
+#include <xen/smp.h>
+
+/* tp points to one of these per cpu */
+struct pcpu_info pcpu_info[NR_CPUS];
\ No newline at end of file
diff --git a/xen/arch/riscv/smpboot.c b/xen/arch/riscv/smpboot.c
new file mode 100644
index 0000000000..a90401ffd4
--- /dev/null
+++ b/xen/arch/riscv/smpboot.c
@@ -0,0 +1,12 @@
+#include <xen/init.h>
+#include <xen/sections.h>
+#include <xen/smp.h>
+
+unsigned long __cpuid_to_hartid_map[NR_CPUS] __ro_after_init = {
+    [0 ... NR_CPUS-1] = INVALID_HARTID
+};
+
+void __init smp_setup_processor_id(unsigned long boot_cpu_hartid)
+{
+    cpuid_to_hartid_map(0) = boot_cpu_hartid;
+}
-- 
2.45.2