[PATCH v4 4/7] xen/riscv: introduce functionality to work with CPU info

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

Introduce struct pcpu_info to store pCPU-related information.
Initially, it includes only processor_id, but it will be extended
to include guest CPU information and temporary variables for
saving/restoring vCPU registers.

Add set_processor_id() and get_processor_id() functions to set
and retrieve the processor_id stored in pcpu_info.

Introduce cpuid_to_hartid_map[NR_CPUS] to map Xen logical CPUs to
hart IDs (physical CPU IDs). Add auxiliary macros cpuid_to_hartid()
for convenient access to this mapping.

Define smp_processor_id() to provide accurate information,
replacing the previous "dummy" value of 0.

Initialize tp registers to point to pcpu_info[0].
Set processor_id to 0 for logical CPU 0 and store the physical CPU ID
for the current logical CPU in cpuid_to_hartid_map[].

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
Changes in V4:
 - wrap id with () inside set_processor_id().
 - code style fixes
 - update BUG_ON(id > NR_CPUS) in smp_processor_id() and drop the comment
   above BUG_ON().
 - s/__cpuid_to_hartid_map/cpuid_to_hartid_map
 - s/cpuid_to_hartid_map/cpuid_to_harti ( here cpuid_to_hartid_map is the name
   of the macros ).
 - update the commit message above the code of TP register initialization in
   start_xen().
 - s/smp_setup_processor_id/smp_setup_bootcpu_id
 - update the commit message.
 - cleanup headers which are included in <asm/processor.h>
---
Changes in V3:
 - new patch.
---
 xen/arch/riscv/Makefile                |  2 ++
 xen/arch/riscv/include/asm/processor.h | 28 ++++++++++++++++++++++++--
 xen/arch/riscv/include/asm/smp.h       | 10 +++++++++
 xen/arch/riscv/setup.c                 | 14 +++++++++++++
 xen/arch/riscv/smp.c                   |  4 ++++
 xen/arch/riscv/smpboot.c               | 12 +++++++++++
 6 files changed, 68 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..fd4e9b4a37 100644
--- a/xen/arch/riscv/include/asm/processor.h
+++ b/xen/arch/riscv/include/asm/processor.h
@@ -12,8 +12,32 @@
 
 #ifndef __ASSEMBLY__
 
-/* TODO: need to be implemeted */
-#define smp_processor_id() 0
+#include <xen/bug.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();
+
+    BUG_ON(id > NR_CPUS);
+
+    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..9f49d2bc8b 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_set_bootcpu_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(cpu) cpuid_to_hartid_map[cpu]
+
 #endif
 
 /*
diff --git a/xen/arch/riscv/setup.c b/xen/arch/riscv/setup.c
index 13f0e8c77d..c9446e6038 100644
--- a/xen/arch/riscv/setup.c
+++ b/xen/arch/riscv/setup.c
@@ -8,6 +8,7 @@
 #include <public/version.h>
 
 #include <asm/early_printk.h>
+#include <asm/smp.h>
 #include <asm/traps.h>
 
 void arch_get_xen_caps(xen_capabilities_info_t *info)
@@ -40,6 +41,19 @@ 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() ( 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_set_bootcpu_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..779d955e3a
--- /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];
diff --git a/xen/arch/riscv/smpboot.c b/xen/arch/riscv/smpboot.c
new file mode 100644
index 0000000000..6690522a52
--- /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_set_bootcpu_id(unsigned long boot_cpu_hartid)
+{
+    cpuid_to_hartid(0) = boot_cpu_hartid;
+}
-- 
2.45.2