[Qemu-devel] [RFC 08/17] ppc: Rewrite ppc_get_compat_smt_threads()

[David Gibson]

To continue consolidation of compatibility mode information, this rewrites
the ppc_get_compat_smt_threads() function using the table of compatiblity
modes in target-ppc/compat.c.

It's not a direct replacement, the new ppc_compat_max_threads() function
has simpler semantics - it just returns the number of threads the cpu
model has, taking into account any compatiblity mode it is in.

This no longer takes into account kvmppc_smt_threads() as the previous
version did.  That check wasn't useful because we check elsewhere that
CPUs aren't instantiated with more threads than kvm allows (or if we didn't
things will already be broken and this won't make it any worse).

Signed-off-by: David Gibson <address@hidden>
---
 hw/ppc/spapr.c              |  8 ++++----
 target-ppc/compat.c         | 18 ++++++++++++++++++
 target-ppc/cpu.h            |  2 +-
 target-ppc/translate_init.c | 20 --------------------
 4 files changed, 23 insertions(+), 25 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 276cefa..6c78889 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -207,6 +207,7 @@ static int spapr_fixup_cpu_dt(void *fdt, sPAPRMachineState 
*spapr)
         PowerPCCPU *cpu = POWERPC_CPU(cs);
         DeviceClass *dc = DEVICE_GET_CLASS(cs);
         int index = ppc_get_vcpu_dt_id(cpu);
+        int compat_smt = MIN(smp_threads, ppc_compat_max_threads(cpu));
 
         if ((index % smt) != 0) {
             continue;
@@ -241,8 +242,7 @@ static int spapr_fixup_cpu_dt(void *fdt, sPAPRMachineState 
*spapr)
             return ret;
         }
 
-        ret = spapr_fixup_cpu_smt_dt(fdt, offset, cpu,
-                                     ppc_get_compat_smt_threads(cpu));
+        ret = spapr_fixup_cpu_smt_dt(fdt, offset, cpu, compat_smt);
         if (ret < 0) {
             return ret;
         }
@@ -408,6 +408,7 @@ static void spapr_populate_cpu_dt(CPUState *cs, void *fdt, 
int offset,
     size_t page_sizes_prop_size;
     uint32_t vcpus_per_socket = smp_threads * smp_cores;
     uint32_t pft_size_prop[] = {0, cpu_to_be32(spapr->htab_shift)};
+    int compat_smt = MIN(smp_threads, ppc_compat_max_threads(cpu));
     sPAPRDRConnector *drc;
     sPAPRDRConnectorClass *drck;
     int drc_index;
@@ -495,8 +496,7 @@ static void spapr_populate_cpu_dt(CPUState *cs, void *fdt, 
int offset,
 
     _FDT(spapr_fixup_cpu_numa_dt(fdt, offset, cs));
 
-    _FDT(spapr_fixup_cpu_smt_dt(fdt, offset, cpu,
-                                ppc_get_compat_smt_threads(cpu)));
+    _FDT(spapr_fixup_cpu_smt_dt(fdt, offset, cpu, compat_smt));
 }
 
 static void spapr_populate_cpus_dt_node(void *fdt, sPAPRMachineState *spapr)
diff --git a/target-ppc/compat.c b/target-ppc/compat.c
index f3fd9c6..66529a6 100644
--- a/target-ppc/compat.c
+++ b/target-ppc/compat.c
@@ -28,6 +28,7 @@
 typedef struct {
     uint32_t pvr;
     uint64_t pcr;
+    int max_threads;
 } CompatInfo;
 
 static const CompatInfo compat_table[] = {
@@ -35,18 +36,22 @@ static const CompatInfo compat_table[] = {
         .pvr = CPU_POWERPC_LOGICAL_2_05,
         .pcr = PCR_COMPAT_2_07 | PCR_COMPAT_2_06 | PCR_COMPAT_2_05
                | PCR_TM_DIS | PCR_VSX_DIS,
+        .max_threads = 2,
     },
     { /* POWER7, ISA2.06 */
         .pvr = CPU_POWERPC_LOGICAL_2_06,
         .pcr = PCR_COMPAT_2_07 | PCR_COMPAT_2_06 | PCR_TM_DIS,
+        .max_threads = 4,
     },
     {
         .pvr = CPU_POWERPC_LOGICAL_2_06_PLUS,
         .pcr = PCR_COMPAT_2_07 | PCR_COMPAT_2_06 | PCR_TM_DIS,
+        .max_threads = 4,
     },
     { /* POWER8, ISA2.07 */
         .pvr = CPU_POWERPC_LOGICAL_2_07,
         .pcr = PCR_COMPAT_2_07,
+        .max_threads = 8,
     },
 };
 
@@ -89,3 +94,16 @@ void ppc_set_compat(PowerPCCPU *cpu, uint32_t compat_pvr, 
Error **errp)
         }
     }
 }
+
+int ppc_compat_max_threads(PowerPCCPU *cpu)
+{
+    const CompatInfo *compat = compat_by_pvr(cpu->compat_pvr);
+    int n_threads = CPU(cpu)->nr_threads;
+
+    if (cpu->compat_pvr) {
+        g_assert(compat);
+        n_threads = MIN(n_threads, compat->max_threads);
+    }
+
+    return n_threads;
+}
diff --git a/target-ppc/cpu.h b/target-ppc/cpu.h
index 15d5e4b..cfda7b2 100644
--- a/target-ppc/cpu.h
+++ b/target-ppc/cpu.h
@@ -1241,7 +1241,6 @@ void ppc_store_sdr1 (CPUPPCState *env, target_ulong 
value);
 void ppc_store_msr (CPUPPCState *env, target_ulong value);
 
 void ppc_cpu_list (FILE *f, fprintf_function cpu_fprintf);
-int ppc_get_compat_smt_threads(PowerPCCPU *cpu);
 #if defined(TARGET_PPC64)
 #endif
 
@@ -1316,6 +1315,7 @@ static inline int cpu_mmu_index (CPUPPCState *env, bool 
ifetch)
 /* Compatibility modes */
 #if defined(TARGET_PPC64)
 void ppc_set_compat(PowerPCCPU *cpu, uint32_t compat_pvr, Error **errp);
+int ppc_compat_max_threads(PowerPCCPU *cpu);
 #endif /* defined(TARGET_PPC64) */
 
 #include "exec/cpu-all.h"
diff --git a/target-ppc/translate_init.c b/target-ppc/translate_init.c
index a70eafb..ba48242 100644
--- a/target-ppc/translate_init.c
+++ b/target-ppc/translate_init.c
@@ -9952,26 +9952,6 @@ static void ppc_cpu_unrealizefn(DeviceState *dev, Error 
**errp)
     }
 }
 
-int ppc_get_compat_smt_threads(PowerPCCPU *cpu)
-{
-    CPUState *cs = CPU(cpu);
-    int ret = MIN(cs->nr_threads, kvmppc_smt_threads());
-
-    switch (cpu->compat_pvr) {
-    case CPU_POWERPC_LOGICAL_2_05:
-        ret = MIN(ret, 2);
-        break;
-    case CPU_POWERPC_LOGICAL_2_06:
-        ret = MIN(ret, 4);
-        break;
-    case CPU_POWERPC_LOGICAL_2_07:
-        ret = MIN(ret, 8);
-        break;
-    }
-
-    return ret;
-}
-
 static gint ppc_cpu_compare_class_pvr(gconstpointer a, gconstpointer b)
 {
     ObjectClass *oc = (ObjectClass *)a;
-- 
2.7.4