Re: [Qemu-devel] [PATCH] Introduce machine specific default memory size

[Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>]

Markus Armbruster <armbru@redhat.com> writes:

> Nikunj A Dadhania <nikunj@linux.vnet.ibm.com> writes:
>
>> diff --git a/vl.c b/vl.c
>> index eb89d62..dd56754 100644
>> --- a/vl.c
>> +++ b/vl.c
>> @@ -4053,6 +4053,18 @@ int main(int argc, char **argv, char **envp)
>>          exit(1);
>>      }
>>  
>> +    if (machine_class->default_ram_size && ram_size < machine_class->default_ram_size) {
>> +        fprintf(stderr, "qemu: %s guest ram size defaulting to %ld MB\n",
>> +                machine_class->name,
>> +                machine_class->default_ram_size / (1024 * 1024));
>
> If the user explicitly asks for something, we either provide it
> silently, or we error out.  This does neither.  Why?

In case the user has provided memory not enough to boot the machine, I
could error out. My idea was to have a sane default which is provided by
the machine.

Initially, I had just "ram_size == default_ram_size", but then it was
allowing "-m 128M" to go through. And the VM would not boot. 

This can as well be converted to an error report and fail here to boot
the VM.

>
>> +        ram_size = machine_class->default_ram_size;
>> +
>> +        /* if maxram size is not provided in options use machine default */
>> +        if (maxram_size == default_ram_size) {
>> +            maxram_size = machine_class->default_ram_size;
>> +        }
>> +    }
>> +
>>      /* store value for the future use */
>>      qemu_opt_set_number(qemu_find_opts_singleton("memory"), "size", ram_size);
>
> Does not apply to master, please name your prerequisite patches or
> rebase.


Rebased patch:


    Introduce machine specific default memory size
    
    Qemu default memory of 128MB is not enough to boot sPAPR
    guest. Introduce a member in the machine class to override the default
    memory size enforced by qemu.
    
    Signed-off-by: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 23cde20..f6b1137 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1738,6 +1738,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
     mc->max_cpus = MAX_CPUS;
     mc->no_parallel = 1;
     mc->default_boot_order = NULL;
+    mc->default_ram_size = SPAPR_DEFAULT_RAM_SIZE;
     mc->kvm_type = spapr_kvm_type;
     mc->has_dynamic_sysbus = true;
 
diff --git a/include/hw/boards.h b/include/hw/boards.h
index 3ddc449..b2b4698 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -108,6 +108,7 @@ struct MachineClass {
     const char *default_display;
     GlobalProperty *compat_props;
     const char *hw_version;
+    ram_addr_t default_ram_size;
 
     HotplugHandler *(*get_hotplug_handler)(MachineState *machine,
                                            DeviceState *dev);
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index 716bff4..d401dd0 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -444,6 +444,9 @@ int spapr_rtas_device_tree_setup(void *fdt, hwaddr rtas_addr,
 #define SPAPR_VIO_BASE_LIOBN    0x00000000
 #define SPAPR_PCI_BASE_LIOBN    0x80000000
 
+/* Default to 1GB guest ram_size */
+#define SPAPR_DEFAULT_RAM_SIZE  (1ULL << 30)
+
 #define RTAS_ERROR_LOG_MAX      2048
 
 typedef struct sPAPRTCETable sPAPRTCETable;
diff --git a/vl.c b/vl.c
index 801d487..4519ccc 100644
--- a/vl.c
+++ b/vl.c
@@ -2684,6 +2684,18 @@ static void set_memory_options(uint64_t *ram_slots, ram_addr_t *maxram_size)
         exit(EXIT_FAILURE);
     }
 
+    if (machine_class->default_ram_size && ram_size < machine_class->default_ram_size) {
+        fprintf(stderr, "qemu: %s guest ram size defaulting to %ld MB\n",
+                machine_class->name,
+                machine_class->default_ram_size / (1024 * 1024));
+        ram_size = machine_class->default_ram_size;
+
+        /* if maxram size is not provided in options use machine default */
+        if (maxram_size == default_ram_size) {
+            maxram_size = machine_class->default_ram_size;
+        }
+    }
+
     /* store value for the future use */
     qemu_opt_set_number(opts, "size", ram_size, &error_abort);
     *maxram_size = ram_size;