Re: [Qemu-devel] [PATCH 3/9] cpu/topology: add uncommon arch support for smp machine properties

[Like Xu <like.xu@linux.intel.com>]

On 2019/4/8 20:54, Igor Mammedov wrote:
> On Fri, 29 Mar 2019 16:48:39 +0800
> Like Xu <like.xu@linux.intel.com> wrote:
> 
> here should be a commit message explaining what patch does
> in more detail.
> 
> 
>> Signed-off-by: Like Xu <like.xu@linux.intel.com>
> 
> Generic note, try not call qdev_get_machine() every time
> you replace smp_cpus or other variables. It's often possible
> to pass MachineState via call chain with trivial fixups.

Hi Igor,

I have some doubts on this comments after some attempts.

I'm not sure if this idea could apply to all qdev_get_machine()
usages in tree or just for this smp-touch-only patch.

It takes a lot of efforts on hooks overrides when we
undo calls to qdev_get_machine() with modification of incoming parameters.

The implementation of qdev_get_machine() couldn't be simpler more
and it doesn't seem to bring much overhead compared with parameter stack.

> 
>> ---
>>   hw/alpha/dp264.c     | 1 +
>>   hw/hppa/machine.c    | 4 ++++
>>   hw/mips/boston.c     | 1 +
>>   hw/mips/mips_malta.c | 9 +++++++++
>>   hw/sparc/sun4m.c     | 2 ++
>>   hw/sparc64/sun4u.c   | 2 ++
>>   hw/xtensa/sim.c      | 1 +
>>   hw/xtensa/xtfpga.c   | 1 +
>>   8 files changed, 21 insertions(+)
>>
>> diff --git a/hw/alpha/dp264.c b/hw/alpha/dp264.c
>> index 0347eb8..ee5d432 100644
>> --- a/hw/alpha/dp264.c
>> +++ b/hw/alpha/dp264.c
>> @@ -63,6 +63,7 @@ static void clipper_init(MachineState *machine)
>>       char *palcode_filename;
>>       uint64_t palcode_entry, palcode_low, palcode_high;
>>       uint64_t kernel_entry, kernel_low, kernel_high;
>> +    unsigned int smp_cpus = machine->topo.smp_cpus;
>>   
>>       /* Create up to 4 cpus.  */
>>       memset(cpus, 0, sizeof(cpus));
>> diff --git a/hw/hppa/machine.c b/hw/hppa/machine.c
>> index d1b1d3c..f652891 100644
>> --- a/hw/hppa/machine.c
>> +++ b/hw/hppa/machine.c
>> @@ -16,6 +16,7 @@
>>   #include "hw/ide.h"
>>   #include "hw/timer/i8254.h"
>>   #include "hw/char/serial.h"
>> +#include "hw/boards.h"
>>   #include "hppa_sys.h"
>>   #include "qemu/units.h"
>>   #include "qapi/error.h"
>> @@ -72,6 +73,7 @@ static void machine_hppa_init(MachineState *machine)
>>       MemoryRegion *ram_region;
>>       MemoryRegion *cpu_region;
>>       long i;
>> +    unsigned int smp_cpus = machine->topo.smp_cpus;
> I'd prefer to replace smp_cpus with machine->topo.smp_cpus
> directly at places it's used, as it makes affected sites
> more visible in the patch.
> And use local smp_cpus only in places where using machine->topo.smp_cpus
> makes core less readable.
> (but it's just personal preference so I don't insist on it)
> 
>>   
>>       ram_size = machine->ram_size;
>>   
>> @@ -242,7 +244,9 @@ static void machine_hppa_init(MachineState *machine)
>>   
>>   static void hppa_machine_reset(void)
>>   {
>> +    MachineState *ms = MACHINE(qdev_get_machine());
>>       int i;
>> +    unsigned int smp_cpus = ms->topo.smp_cpus;
> 
> ***)
> It would be better to pass MachineState as argument to
> hppa_machine_reset(), a patch to so should go before this one.
> 
> Quick look shows only 3 overrides (hppa, pc, pnv) and one caller,
> so I'd rather fix it than calling qdev_get_machine() unnecessarily
> 
>>   
>>       qemu_devices_reset();
>>   
>> diff --git a/hw/mips/boston.c b/hw/mips/boston.c
>> index e5bab3c..7752c10 100644
>> --- a/hw/mips/boston.c
>> +++ b/hw/mips/boston.c
>> @@ -434,6 +434,7 @@ static void boston_mach_init(MachineState *machine)
>>       DriveInfo *hd[6];
>>       Chardev *chr;
>>       int fw_size, fit_err;
>> +    unsigned int smp_cpus = machine->topo.smp_cpus;
>>       bool is_64b;
>>   
>>       if ((machine->ram_size % GiB) ||
>> diff --git a/hw/mips/mips_malta.c b/hw/mips/mips_malta.c
>> index 439665a..d595375 100644
>> --- a/hw/mips/mips_malta.c
>> +++ b/hw/mips/mips_malta.c
>> @@ -1095,6 +1095,8 @@ static int64_t load_kernel (void)
>>   
>>   static void malta_mips_config(MIPSCPU *cpu)
>>   {
>> +    MachineState *ms = MACHINE(qdev_get_machine());
>> +    unsigned int smp_cpus = ms->topo.smp_cpus;
>>       CPUMIPSState *env = &cpu->env;
>>       CPUState *cs = CPU(cpu);
> this one also called from reset, so the same [***] applies here too.
> 
>>   
>> @@ -1127,9 +1129,11 @@ static void main_cpu_reset(void *opaque)
>>   static void create_cpu_without_cps(const char *cpu_type,
>>                                      qemu_irq *cbus_irq, qemu_irq *i8259_irq)
>>   {
>> +    MachineState *ms = MACHINE(qdev_get_machine());
> caller has an access to MachineState so pass it down call chain all the way
> 
>>       CPUMIPSState *env;
>>       MIPSCPU *cpu;
>>       int i;
>> +    unsigned int smp_cpus = ms->topo.smp_cpus;
>>   
>>       for (i = 0; i < smp_cpus; i++) {
>>           cpu = MIPS_CPU(cpu_create(cpu_type));
>> @@ -1149,7 +1153,9 @@ static void create_cpu_without_cps(const char *cpu_type,
>>   static void create_cps(MaltaState *s, const char *cpu_type,
>>                          qemu_irq *cbus_irq, qemu_irq *i8259_irq)
>>   {
>> +    MachineState *ms = MACHINE(qdev_get_machine());
> ditto
> 
>>       Error *err = NULL;
>> +    unsigned int smp_cpus = ms->topo.smp_cpus;
>>   
>>       s->cps = MIPS_CPS(object_new(TYPE_MIPS_CPS));
>>       qdev_set_parent_bus(DEVICE(s->cps), sysbus_get_default());
>> @@ -1171,6 +1177,9 @@ static void create_cps(MaltaState *s, const char *cpu_type,
>>   static void mips_create_cpu(MaltaState *s, const char *cpu_type,
>>                               qemu_irq *cbus_irq, qemu_irq *i8259_irq)
>>   {
>> +    MachineState *ms = MACHINE(qdev_get_machine());
> ditto
> 
>> +    unsigned int smp_cpus = ms->topo.smp_cpus;
>> +
>>       if ((smp_cpus > 1) && cpu_supports_cps_smp(cpu_type)) {
>>           create_cps(s, cpu_type, cbus_irq, i8259_irq);
>>       } else {
>> diff --git a/hw/sparc/sun4m.c b/hw/sparc/sun4m.c
>> index ca1e382..2321cfb 100644
>> --- a/hw/sparc/sun4m.c
>> +++ b/hw/sparc/sun4m.c
>> @@ -853,6 +853,8 @@ static void sun4m_hw_init(const struct sun4m_hwdef *hwdef,
>>       unsigned int num_vsimms;
>>       DeviceState *dev;
>>       SysBusDevice *s;
>> +    unsigned int smp_cpus = machine->topo.smp_cpus;
>> +    unsigned int max_cpus = machine->topo.max_cpus;
>>   
>>       /* init CPUs */
>>       for(i = 0; i < smp_cpus; i++) {
>> diff --git a/hw/sparc64/sun4u.c b/hw/sparc64/sun4u.c
>> index 399f2d7..d089c4d 100644
>> --- a/hw/sparc64/sun4u.c
>> +++ b/hw/sparc64/sun4u.c
>> @@ -546,6 +546,8 @@ static void sun4uv_init(MemoryRegion *address_space_mem,
>>       NICInfo *nd;
>>       MACAddr macaddr;
>>       bool onboard_nic;
>> +    unsigned int smp_cpus = machine->topo.smp_cpus;
>> +    unsigned int max_cpus = machine->topo.max_cpus;
>>   
>>       /* init CPUs */
>>       cpu = sparc64_cpu_devinit(machine->cpu_type, hwdef->prom_addr);
>> diff --git a/hw/xtensa/sim.c b/hw/xtensa/sim.c
>> index 12c7437..cc0396b 100644
>> --- a/hw/xtensa/sim.c
>> +++ b/hw/xtensa/sim.c
>> @@ -59,6 +59,7 @@ static void xtensa_sim_init(MachineState *machine)
>>       ram_addr_t ram_size = machine->ram_size;
>>       const char *kernel_filename = machine->kernel_filename;
>>       int n;
>> +    unsigned int smp_cpus = machine->topo.smp_cpus;
>>   
>>       for (n = 0; n < smp_cpus; n++) {
>>           cpu = XTENSA_CPU(cpu_create(machine->cpu_type));
>> diff --git a/hw/xtensa/xtfpga.c b/hw/xtensa/xtfpga.c
>> index e05ef75..f71a15e 100644
>> --- a/hw/xtensa/xtfpga.c
>> +++ b/hw/xtensa/xtfpga.c
>> @@ -238,6 +238,7 @@ static void xtfpga_init(const XtfpgaBoardDesc *board, MachineState *machine)
>>       const unsigned system_io_size = 224 * MiB;
>>       uint32_t freq = 10000000;
>>       int n;
>> +    unsigned int smp_cpus = machine->topo.smp_cpus;
>>   
>>       if (smp_cpus > 1) {
>>           mx_pic = xtensa_mx_pic_init(31);
> 
>