Re: [RFC PATCH 2/5] RISC-V: Use Linux logical cpu number instead of hartid

[Atish Patra <atish.patra@wdc.com>]

On 8/15/18 9:24 PM, Anup Patel wrote:
> On Thu, Aug 16, 2018 at 5:26 AM, Atish Patra <atish.patra@wdc.com> wrote:
>> Setup the cpu_logical_map during boot. Moreover, every SBI call
>> and PLIC context are based on the physical hartid. Use the logical
>> cpu to hartid mapping to pass correct hartid to respective functions.
>>
>> Signed-off-by: Atish Patra <atish.patra@wdc.com>
>> ---
>>   arch/riscv/include/asm/tlbflush.h | 17 +++++++++++++----
>>   arch/riscv/kernel/cpu.c           |  4 +++-
>>   arch/riscv/kernel/setup.c         | 10 ++++++++++
>>   arch/riscv/kernel/smp.c           | 24 +++++++++++++++---------
>>   arch/riscv/kernel/smpboot.c       | 30 ++++++++++++++++++------------
>>   drivers/clocksource/riscv_timer.c | 12 ++++++++----
>>   drivers/irqchip/irq-sifive-plic.c | 11 +++++++----
>>   7 files changed, 74 insertions(+), 34 deletions(-)
>>
>> diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h
>> index 85c2d8ba..ecfd9b0e 100644
>> --- a/arch/riscv/include/asm/tlbflush.h
>> +++ b/arch/riscv/include/asm/tlbflush.h
>> @@ -16,6 +16,7 @@
>>   #define _ASM_RISCV_TLBFLUSH_H
>>
>>   #include <linux/mm_types.h>
>> +#include <asm/smp.h>
>>
>>   /*
>>    * Flush entire local TLB.  'sfence.vma' implicitly fences with the instruction
>> @@ -49,13 +50,21 @@ static inline void flush_tlb_range(struct vm_area_struct *vma,
>>
>>   #include <asm/sbi.h>
>>
>> -#define flush_tlb_all() sbi_remote_sfence_vma(NULL, 0, -1)
>> +static inline void remote_sfence_vma(struct cpumask *cmask, unsigned long start,
>> +                                    unsigned long size)
>> +{
>> +       struct cpumask hmask;
>> +
>> +       cpuid_to_hartid_mask(cmask, &hmask);
>> +       sbi_remote_sfence_vma(hmask.bits, start, size);
>> +}
>> +
>> +#define flush_tlb_all() remote_sfence_vma(NULL, 0, -1)
>>   #define flush_tlb_page(vma, addr) flush_tlb_range(vma, addr, 0)
>>   #define flush_tlb_range(vma, start, end) \
>> -       sbi_remote_sfence_vma(mm_cpumask((vma)->vm_mm)->bits, \
>> -                             start, (end) - (start))
>> +       remote_sfence_vma(mm_cpumask((vma)->vm_mm), start, (end) - (start))
>>   #define flush_tlb_mm(mm) \
>> -       sbi_remote_sfence_vma(mm_cpumask(mm)->bits, 0, -1)
>> +       remote_sfence_vma(mm_cpumask(mm), 0, -1)
>>
>>   #endif /* CONFIG_SMP */
>>
>> diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
>> index ca6c81e5..f8a18ace 100644
>> --- a/arch/riscv/kernel/cpu.c
>> +++ b/arch/riscv/kernel/cpu.c
>> @@ -14,6 +14,7 @@
>>   #include <linux/init.h>
>>   #include <linux/seq_file.h>
>>   #include <linux/of.h>
>> +#include <asm/smp.h>
>>
>>   /* Return -1 if not a valid hart */
>>   int riscv_of_processor_hart(struct device_node *node)
>> @@ -79,7 +80,8 @@ static void c_stop(struct seq_file *m, void *v)
>>   static int c_show(struct seq_file *m, void *v)
>>   {
>>          unsigned long hart_id = (unsigned long)v - 1;
>> -       struct device_node *node = of_get_cpu_node(hart_id, NULL);
>> +       struct device_node *node = of_get_cpu_node(cpu_logical_map(hart_id),
>> +                                                  NULL);
> 
> The hart_id is misleading name here. It should be cpu_id. Please replace
> all instances of hart_id with cpu_id and where hard ID is to be displayed
> use cpu_logical_map(cpu_id).
> 
Correct. Thanks for catching it. I will fix it in v2.


>>          const char *compat, *isa, *mmu;
>>
>>          seq_printf(m, "hart\t: %lu\n", hart_id);
>> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
>> index e21ed481..97b586f8 100644
>> --- a/arch/riscv/kernel/setup.c
>> +++ b/arch/riscv/kernel/setup.c
>> @@ -84,6 +84,16 @@ atomic_t hart_lottery;
>>
>>   u64 __cpu_logical_map[NR_CPUS];
>>
>> +void __init smp_setup_processor_id(void)
>> +{
>> +       int cpu = smp_processor_id();
>> +
>> +       cpu_logical_map(0) = cpu;
> 
> I think this should be:
> cpu_logical_map(cpu) = hart_id;
> 
> Here hart_id for boot CPU will be value of a0 register passed at boot-time.
> 
I will change the variable name to hart_id. The assembly code in head.S 
have already stored hart id in thread info structure. So 
smp_processor_id() and hart id would be the same.


Regards,
Atish
>> +
>> +       /* Change the boot cpu ID in thread_info */
>> +       current->thread_info.cpu = 0;
>> +}
>> +
>>   #ifdef CONFIG_BLK_DEV_INITRD
>>   static void __init setup_initrd(void)
>>   {
>> diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
>> index d55379ee..4ab70480 100644
>> --- a/arch/riscv/kernel/smp.c
>> +++ b/arch/riscv/kernel/smp.c
>> @@ -97,14 +97,18 @@ void riscv_software_interrupt(void)
>>   static void
>>   send_ipi_message(const struct cpumask *to_whom, enum ipi_message_type operation)
>>   {
>> -       int i;
>> +       int cpuid, hartid;
>> +       struct cpumask hartid_mask;
>>
>> +       cpumask_clear(&hartid_mask);
>>          mb();
>> -       for_each_cpu(i, to_whom)
>> -               set_bit(operation, &ipi_data[i].bits);
>> -
>> +       for_each_cpu(cpuid, to_whom) {
>> +               set_bit(operation, &ipi_data[cpuid].bits);
>> +               hartid = cpu_logical_map(cpuid);
>> +               cpumask_set_cpu(hartid, &hartid_mask);
>> +       }
>>          mb();
>> -       sbi_send_ipi(cpumask_bits(to_whom));
>> +       sbi_send_ipi(cpumask_bits(&hartid_mask));
>>   }
>>
>>   void arch_send_call_function_ipi_mask(struct cpumask *mask)
>> @@ -146,7 +150,7 @@ void smp_send_reschedule(int cpu)
>>   void flush_icache_mm(struct mm_struct *mm, bool local)
>>   {
>>          unsigned int cpu;
>> -       cpumask_t others, *mask;
>> +       cpumask_t others, hmask, *mask;
>>
>>          preempt_disable();
>>
>> @@ -164,9 +168,11 @@ void flush_icache_mm(struct mm_struct *mm, bool local)
>>           */
>>          cpumask_andnot(&others, mm_cpumask(mm), cpumask_of(cpu));
>>          local |= cpumask_empty(&others);
>> -       if (mm != current->active_mm || !local)
>> -               sbi_remote_fence_i(others.bits);
>> -       else {
>> +       if (mm != current->active_mm || !local) {
>> +               cpumask_clear(&hmask);
>> +               cpuid_to_hartid_mask(&others, &hmask);
>> +               sbi_remote_fence_i(hmask.bits);
>> +       } else {
>>                  /*
>>                   * It's assumed that at least one strongly ordered operation is
>>                   * performed on this hart between setting a hart's cpumask bit
>> diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
>> index 56abab6a..6ab2bb1b 100644
>> --- a/arch/riscv/kernel/smpboot.c
>> +++ b/arch/riscv/kernel/smpboot.c
>> @@ -50,27 +50,33 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
>>   void __init setup_smp(void)
>>   {
>>          struct device_node *dn = NULL;
>> -       int hart, im_okay_therefore_i_am = 0;
>> +       int hart, found_boot_cpu = 0;
>> +       int cpuid = 1;
>>
>>          while ((dn = of_find_node_by_type(dn, "cpu"))) {
>>                  hart = riscv_of_processor_hart(dn);
>> -               if (hart >= 0) {
>> -                       set_cpu_possible(hart, true);
>> -                       set_cpu_present(hart, true);
>> -                       if (hart == smp_processor_id()) {
>> -                               BUG_ON(im_okay_therefore_i_am);
>> -                               im_okay_therefore_i_am = 1;
>> -                       }
>> +
>> +               if (hart < 0)
>> +                       continue;
>> +               if (hart == cpu_logical_map(0)) {
>> +                       BUG_ON(found_boot_cpu);
>> +                       found_boot_cpu = 1;
>> +                       continue;
>>                  }
>> +
>> +               cpu_logical_map(cpuid) = hart;
>> +               set_cpu_possible(cpuid, true);
>> +               set_cpu_present(cpuid, true);
>> +               cpuid++;
>>          }
>>
>> -       BUG_ON(!im_okay_therefore_i_am);
>> +       BUG_ON(!found_boot_cpu);
>>   }
>>
>>   int __cpu_up(unsigned int cpu, struct task_struct *tidle)
>>   {
>> +       int hartid = cpu_logical_map(cpu);
>>          tidle->thread_info.cpu = cpu;
>> -
>>          /*
>>           * On RISC-V systems, all harts boot on their own accord.  Our _start
>>           * selects the first hart to boot the kernel and causes the remainder
>> @@ -79,8 +85,8 @@ int __cpu_up(unsigned int cpu, struct task_struct *tidle)
>>           * the spinning harts that they can continue the boot process.
>>           */
>>          smp_mb();
>> -       __cpu_up_stack_pointer[cpu] = task_stack_page(tidle) + THREAD_SIZE;
>> -       __cpu_up_task_pointer[cpu] = tidle;
>> +       __cpu_up_stack_pointer[hartid] = task_stack_page(tidle) + THREAD_SIZE;
>> +       __cpu_up_task_pointer[hartid] = tidle;
>>
>>          while (!cpu_online(cpu))
>>                  cpu_relax();
>> diff --git a/drivers/clocksource/riscv_timer.c b/drivers/clocksource/riscv_timer.c
>> index 4e8b347e..f1f205e5 100644
>> --- a/drivers/clocksource/riscv_timer.c
>> +++ b/drivers/clocksource/riscv_timer.c
>> @@ -8,6 +8,7 @@
>>   #include <linux/cpu.h>
>>   #include <linux/delay.h>
>>   #include <linux/irq.h>
>> +#include <asm/smp.h>
>>   #include <asm/sbi.h>
>>
>>   /*
>> @@ -84,13 +85,16 @@ void riscv_timer_interrupt(void)
>>
>>   static int __init riscv_timer_init_dt(struct device_node *n)
>>   {
>> -       int cpu_id = riscv_of_processor_hart(n), error;
>> +       int cpuid, hartid, error;
>>          struct clocksource *cs;
>>
>> -       if (cpu_id != smp_processor_id())
>> +       hartid = riscv_of_processor_hart(n);
>> +       cpuid = riscv_hartid_to_cpuid(hartid);
>> +
>> +       if (cpuid != smp_processor_id())
>>                  return 0;
>>
>> -       cs = per_cpu_ptr(&riscv_clocksource, cpu_id);
>> +       cs = per_cpu_ptr(&riscv_clocksource, cpuid);
>>          clocksource_register_hz(cs, riscv_timebase);
>>
>>          error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING,
>> @@ -98,7 +102,7 @@ static int __init riscv_timer_init_dt(struct device_node *n)
>>                           riscv_timer_starting_cpu, riscv_timer_dying_cpu);
>>          if (error)
>>                  pr_err("RISCV timer register failed [%d] for cpu = [%d]\n",
>> -                      error, cpu_id);
>> +                      error, cpuid);
>>          return error;
>>   }
>>
>> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
>> index 298685e5..2eb2e78c 100644
>> --- a/drivers/irqchip/irq-sifive-plic.c
>> +++ b/drivers/irqchip/irq-sifive-plic.c
>> @@ -15,6 +15,7 @@
>>   #include <linux/of_irq.h>
>>   #include <linux/platform_device.h>
>>   #include <linux/spinlock.h>
>> +#include <asm/smp.h>
>>
>>   /*
>>    * This driver implements a version of the RISC-V PLIC with the actual layout
>> @@ -93,10 +94,11 @@ static inline void plic_toggle(int ctxid, int hwirq, int enable)
>>   static inline void plic_irq_toggle(struct irq_data *d, int enable)
>>   {
>>          int cpu;
>> +       struct plic_handler *handler;
>>
>>          writel(enable, plic_regs + PRIORITY_BASE + d->hwirq * PRIORITY_PER_ID);
>>          for_each_cpu(cpu, irq_data_get_affinity_mask(d)) {
>> -               struct plic_handler *handler = per_cpu_ptr(&plic_handlers, cpu);
>> +               handler = per_cpu_ptr(&plic_handlers, cpu);
>>
>>                  if (handler->present)
>>                          plic_toggle(handler->ctxid, d->hwirq, enable);
>> @@ -217,7 +219,7 @@ static int __init plic_init(struct device_node *node,
>>                  struct of_phandle_args parent;
>>                  struct plic_handler *handler;
>>                  irq_hw_number_t hwirq;
>> -               int cpu;
>> +               int cpu, hartid;
>>
>>                  if (of_irq_parse_one(node, i, &parent)) {
>>                          pr_err("failed to parse parent for context %d.\n", i);
>> @@ -228,12 +230,13 @@ static int __init plic_init(struct device_node *node,
>>                  if (parent.args[0] == -1)
>>                          continue;
>>
>> -               cpu = plic_find_hart_id(parent.np);
>> -               if (cpu < 0) {
>> +               hartid = plic_find_hart_id(parent.np);
>> +               if (hartid < 0) {
>>                          pr_warn("failed to parse hart ID for context %d.\n", i);
>>                          continue;
>>                  }
>>
>> +               cpu = riscv_hartid_to_cpuid(hartid);
>>                  handler = per_cpu_ptr(&plic_handlers, cpu);
>>                  handler->present = true;
>>                  handler->ctxid = i;
>> --
>> 2.7.4
>>
> 
> Regards,
> Anup
>