Re: [PATCH] target/loongarch: Use physical cpu id about CSR CPUID for sysemu

Thu, 24 Oct 2024 05:07:51 -0700 



On 2024/10/23 上午9:22, maobibo wrote:



On 2024/10/23 上午2:54, Richard Henderson wrote:

On 10/22/24 05:42, Bibo Mao wrote:

For user tcg, there is no physical cpu id provided and logic cpuid
is used. For system emulation, physical cpu id is provided, initial
value of register CSR CPUID can be set from physical cpu id.

Signed-off-by: Bibo Mao <maob...@loongson.cn>
---
  hw/intc/loongarch_ipi.c           | 3 ++-
  target/loongarch/cpu.c            | 7 ++++++-
  target/loongarch/tcg/csr_helper.c | 4 ----
  3 files changed, 8 insertions(+), 6 deletions(-)



Since cpu_index is arbitrary and assigned by hw/loongarch/virt.c 
anyway, why do these two values differ?  Surely arch_id is already 
unique per cpu?

arch_id comes from cpu topo and cpu_index comes from vcpu object created 
order. There are two places where cpu_index may differ from arch_id, 
such as command "-smp 2,maxcpus=16,sockets=4,cores=4,threads=1".



1. If one cpu is hot-added with command "device_add 
la464-loongarch-cpu,socket-id=1,core-id=0,thread-id=0,id=cpu-4". The 
value of cpu_index is 2, however its arch_id is 4.


2. The other condition is not decided now how to generate arch_id, for

the command "-smp 2,maxcpus=36,sockets=6,cores=6,threads=1". It is not 
decided what it max number about one socket, it may be 6, also it may be 
8 which is component of 2.

After second thought, cpu_index can be set again by machines, it can be 
cpuslot index of possible_cpus coming from possible_cpu_arch_ids(). For 
the general arch_id calculation method:

   archid = socket_id * ms->smp.threads * ms->smp.cores  +
            core_id * ms->smp.threads + thread_id
Then arch_id will be the same with cpu_index.


Generic arch_id calculation method is enough, will modify it in furture 
if HW platform defines separate method.


Will refresh the patch in next round.

Regards
Bibo Mao


arch_id comes from cpu topo, it should be unique per cpu.

Regards
Bibo Mao




r~




diff --git a/hw/intc/loongarch_ipi.c b/hw/intc/loongarch_ipi.c
index 2ae1a42c46..78b6fce81b 100644
--- a/hw/intc/loongarch_ipi.c
+++ b/hw/intc/loongarch_ipi.c

@@ -42,7 +42,8 @@ static CPUState *loongarch_cpu_by_arch_id(int64_t 
arch_id)

      CPUArchId *archid;
      archid = find_cpu_by_archid(machine, arch_id);
-    if (archid) {
+    /* For offlined cpus, archid->cpu may be NULL */
+    if (archid && archid->cpu) {
          return CPU(archid->cpu);
      }
diff --git a/target/loongarch/cpu.c b/target/loongarch/cpu.c
index 7212fb5f8f..d4659e8d45 100644
--- a/target/loongarch/cpu.c
+++ b/target/loongarch/cpu.c
@@ -510,8 +510,10 @@ static void loongarch_max_initfn(Object *obj)
  static void loongarch_cpu_reset_hold(Object *obj, ResetType type)
  {
      CPUState *cs = CPU(obj);
+    LoongArchCPU *cpu = LOONGARCH_CPU(obj);
      LoongArchCPUClass *lacc = LOONGARCH_CPU_GET_CLASS(obj);
      CPULoongArchState *env = cpu_env(cs);
+    int n;
      if (lacc->parent_phases.hold) {
          lacc->parent_phases.hold(obj, type);

@@ -522,7 +524,6 @@ static void loongarch_cpu_reset_hold(Object *obj, 
ResetType type)

  #endif
      env->fcsr0 = 0x0;
-    int n;
      /* Set csr registers value after reset, see the manual 6.4. */
      env->CSR_CRMD = FIELD_DP64(env->CSR_CRMD, CSR_CRMD, PLV, 0);
      env->CSR_CRMD = FIELD_DP64(env->CSR_CRMD, CSR_CRMD, IE, 0);

@@ -543,7 +544,11 @@ static void loongarch_cpu_reset_hold(Object 
*obj, ResetType type)

      env->CSR_ESTAT = env->CSR_ESTAT & (~MAKE_64BIT_MASK(0, 2));

      env->CSR_RVACFG = FIELD_DP64(env->CSR_RVACFG, CSR_RVACFG, 
RBITS, 0);

+#ifndef CONFIG_USER_ONLY
+    env->CSR_CPUID = cpu->phy_id;
+#else
      env->CSR_CPUID = cs->cpu_index;
+#endif
      env->CSR_TCFG = FIELD_DP64(env->CSR_TCFG, CSR_TCFG, EN, 0);
      env->CSR_LLBCTL = FIELD_DP64(env->CSR_LLBCTL, CSR_LLBCTL, KLO, 0);

      env->CSR_TLBRERA = FIELD_DP64(env->CSR_TLBRERA, CSR_TLBRERA, 
ISTLBR, 0);
diff --git a/target/loongarch/tcg/csr_helper.c 
b/target/loongarch/tcg/csr_helper.c

index 15f94caefa..2aeca2343d 100644
--- a/target/loongarch/tcg/csr_helper.c
+++ b/target/loongarch/tcg/csr_helper.c
@@ -37,10 +37,6 @@ target_ulong helper_csrrd_pgd(CPULoongArchState *env)
  target_ulong helper_csrrd_cpuid(CPULoongArchState *env)
  {
-    LoongArchCPU *lac = env_archcpu(env);
-
-    env->CSR_CPUID = CPU(lac)->cpu_index;
-
      return env->CSR_CPUID;
  }

base-commit: cc5adbbd50d81555b8eb73602ec16fde40b55be4



























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