[Qemu-devel] [PATCH v2 18/19] target-ppc: Enhance the CPU node labels for the guest device tree for pseries.

[Prerna Saxena <prerna@linux.vnet.ibm.com>]

Hi David,
Thanks for the review feedback. I have incorporated your changes in v2 of
the patch, which follows herewith.

Regards,
Prerna

Subject: [PATCH v2] Target-ppc : Enhance the CPU node labels for the guest
 device tree for pseries.

In absence of a -CPU parameter in the qemu command line, the nodes of
KVM-enabled guest device tree look like this :

/proc/device-tree/cpus/HOST@0/...
/proc/device-tree/cpus/HOST@4/...

This patch replaces this obscure 'HOST' label with a more descriptive label.
This is gathered by first identifying the PVR of the host, and then determining
the host CPU alias which corresponds to the model indicated by this PVR.

Sample Final outcome for an KVM-enabled pseries guest running on POWER7:
/proc/device-tree/cpus/PowerPC,POWER7@0/...
/proc/device-tree/cpus/PowerPC,POWER7@4/...

This also helps userspace tools like ppc64_cpu, which expect the device tree
to be in this format.

Signed-off-by: Prerna Saxena <prerna@linux.vnet.ibm.com>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
---
 hw/ppc/spapr.c              | 18 +++++++++++++++---
 target-ppc/cpu-qom.h        |  1 +
 target-ppc/translate_init.c | 28 ++++++++++++++++++++++++++++
 3 files changed, 44 insertions(+), 3 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index fe34291..ddf263a 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -79,6 +79,7 @@
 
 #define HTAB_SIZE(spapr)        (1ULL << ((spapr)->htab_shift))
 
+#define PPC_DEVTREE_STR         "PowerPC,"
 sPAPREnvironment *spapr;
 
 int spapr_allocate_irq(int hint, bool lsi)
@@ -295,9 +296,12 @@ static void *spapr_create_fdt_skel(const char *cpu_model,
     _FDT((fdt_property_cell(fdt, "#address-cells", 0x1)));
     _FDT((fdt_property_cell(fdt, "#size-cells", 0x0)));
 
-    modelname = g_strdup(cpu_model);
+    /* device tree nodes must look like this :
+     * PowerPC,CPU_ALIAS@0
+     */
+    modelname = g_strdup_printf(PPC_DEVTREE_STR "%s", cpu_model);
 
-    for (i = 0; i < strlen(modelname); i++) {
+    for (i = strlen(PPC_DEVTREE_STR); i < strlen(modelname); i++) {
         modelname[i] = toupper(modelname[i]);
     }
 
@@ -735,7 +739,7 @@ static void ppc_spapr_init(QEMUMachineInitArgs *args)
     MemoryRegion *sysmem = get_system_memory();
     MemoryRegion *ram = g_new(MemoryRegion, 1);
     hwaddr rma_alloc_size;
-    uint32_t initrd_base = 0;
+    uint32_t initrd_base = 0, pvr = 0;
     long kernel_size = 0, initrd_size = 0;
     long load_limit, rtas_limit, fw_size;
     char *filename;
@@ -959,6 +963,14 @@ static void ppc_spapr_init(QEMUMachineInitArgs *args)
 
     spapr->entry_point = 0x100;
 
+#ifdef CONFIG_KVM
+    /* Ensure that cpu_model is correctly reflected for a KVM guest */
+    if (kvm_enabled() && !strcmp(cpu_model, "host")) {
+        asm ("mfpvr %0"
+            : "=r"(pvr));
+        cpu_model = ppc_cpu_alias_by_pvr(pvr);
+    }
+#endif
     /* Prepare the device tree */
     spapr->fdt_skel = spapr_create_fdt_skel(cpu_model,
                                             initrd_base, initrd_size,
diff --git a/target-ppc/cpu-qom.h b/target-ppc/cpu-qom.h
index 84ba105..90dd1dd 100644
--- a/target-ppc/cpu-qom.h
+++ b/target-ppc/cpu-qom.h
@@ -99,6 +99,7 @@ static inline PowerPCCPU *ppc_env_get_cpu(CPUPPCState *env)
 #define ENV_OFFSET offsetof(PowerPCCPU, env)
 
 PowerPCCPUClass *ppc_cpu_class_by_pvr(uint32_t pvr);
+const char *ppc_cpu_alias_by_pvr(uint32_t pvr);
 
 void ppc_cpu_do_interrupt(CPUState *cpu);
 void ppc_cpu_dump_state(CPUState *cpu, FILE *f, fprintf_function cpu_fprintf,
diff --git a/target-ppc/translate_init.c b/target-ppc/translate_init.c
index 50e0ee5..21a7f6f 100644
--- a/target-ppc/translate_init.c
+++ b/target-ppc/translate_init.c
@@ -7913,6 +7913,34 @@ PowerPCCPUClass *ppc_cpu_class_by_pvr(uint32_t pvr)
     return pcc;
 }
 
+const char *ppc_cpu_alias_by_pvr(uint32_t pvr)
+{
+    int i;
+    const char *cpu_alias;
+    char *offset, *model;
+
+    cpu_alias  = object_class_get_name(OBJECT_CLASS
+                            (ppc_cpu_class_by_pvr(pvr)));
+
+    /* Replace the full class name in cpu_alias with the CPU alias
+     * Eg, POWER7_V2.3-POWERPC64-CPU can simply be called
+     * POWER7
+     */
+
+    offset = strstr(cpu_alias, "-" TYPE_POWERPC_CPU);
+    if (offset) {
+        model = g_strndup(cpu_alias, offset - cpu_alias);
+        for (i = 0; ppc_cpu_aliases[i].model != NULL; i++) {
+            if (strcmp(ppc_cpu_aliases[i].model, model) == 0) {
+                g_free(model);
+                return ppc_cpu_aliases[i].alias;
+            }
+        }
+        g_free(model);
+    }
+    return NULL;
+}
+
 static gint ppc_cpu_compare_class_name(gconstpointer a, gconstpointer b)
 {
     ObjectClass *oc = (ObjectClass *)a;
-- 
1.7.11.7



-- 
Prerna Saxena

Linux Technology Centre,
IBM Systems and Technology Lab,
Bangalore, India