Re: [Qemu-devel] [PATCH 3/4] pc: Add 2.9 machine-types

[Laszlo Ersek <lersek@redhat.com>]

On 01/04/17 15:20, Eduardo Habkost wrote:
> On Wed, Jan 04, 2017 at 03:01:07PM +0100, Laszlo Ersek wrote:
>> On 12/27/16 20:21, Eduardo Habkost wrote:
>>> Cc: "Michael S. Tsirkin" <mst@redhat.com>
>>> Cc: Laszlo Ersek <lersek@redhat.com>
>>> Cc: Igor Mammedov <imammedo@redhat.com>
>>> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
>>> ---
>>>  include/hw/i386/pc.h |  1 +
>>>  hw/i386/pc_piix.c    | 15 ++++++++++++---
>>>  hw/i386/pc_q35.c     | 13 +++++++++++--
>>>  3 files changed, 24 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
>>> index b22e699..ceeacca 100644
>>> --- a/include/hw/i386/pc.h
>>> +++ b/include/hw/i386/pc.h
>>> @@ -375,6 +375,7 @@ int e820_get_num_entries(void);
>>>  bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);
>>>  
>>>  #define PC_COMPAT_2_8 \
>>> +    HW_COMPAT_2_8
>>>  
>>>  #define PC_COMPAT_2_7 \
>>>      HW_COMPAT_2_7 \
>>
>> Here I would recommend two things:
>> - introduce an empty PC_COMPAT_2_9 macro
>> - in the PC_COMPAT_2_8 macro being modified, add a trailing backslash
>>   after HW_COMPAT_2_8
>>
>> Both of these aim at keeping up the current pattern; namely, for the
>> most recent machine type, a PC_COMPAT macro should exist (even if empty
>> / unused),
> 
> Why? An empty and unused macro would only confuse people reading
> the code. The empty PC_COMPAT_2_8 macro was added to the 2.8 tree
> by mistake in commit 14c985cffa6c.

* First, the mistake was not in commit 14c985cffa6cb -- I see that "git
blame" fingers that commit, but if you actually show the commit, it
added the macro with a non-empty replacement text:

+#define PC_COMPAT_2_8 \
+    {\
+        .driver   = TYPE_X86_CPU,\
+        .property = "l3-cache",\
+        .value    = "off",\
+    },
+
+

Instead, the mistake was (apparently) in commit 152fcbecad37, where
PC_COMPAT_2_8 was "emptied", but preserved.

* Second, you do realize periodic contributors / reviewers like me
cannot be expected to do a good job writing / reviewing patches if
existing practice in the tree cannot be trusted as example.

If a standalone (empty) PC_COMPAT_2_9 macro is wrong / confusing (which
I agree it could be), then the empty PC_COMPAT_2_8 macro was wrong /
confusing just the same, and the reviewers of 152fcbecad37 should have
arguably caught it at that time.

Anyway, my R-b stands, with whichever updates you prefer from my
suggestions.

Thanks
Laszlo

> 
>>            plus each PC_COMPAT macro should be extensible by plain
>> appending (hence the final trailing backslash).
> 
> Good idea.
> 
>>
>> Functionally the above hunk is good of course, so I'll leave it to you
>> whether you actually want to address my comments.
>>
>> The rest looks fine; I should be able to rebase my broadcast SMI (v5)
>> stuff to this.
>>
>> Changed or unchanged:
>>
>> Reviewed-by: Laszlo Ersek <lersek@redhat.com>
> 
> Thanks!
> 
>>
>> Thanks
>> Laszlo
>>
>>> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
>>> index 5e1adbe..9f102aa 100644
>>> --- a/hw/i386/pc_piix.c
>>> +++ b/hw/i386/pc_piix.c
>>> @@ -437,13 +437,24 @@ static void pc_i440fx_machine_options(MachineClass *m)
>>>      m->default_display = "std";
>>>  }
>>>  
>>> -static void pc_i440fx_2_8_machine_options(MachineClass *m)
>>> +static void pc_i440fx_2_9_machine_options(MachineClass *m)
>>>  {
>>>      pc_i440fx_machine_options(m);
>>>      m->alias = "pc";
>>>      m->is_default = 1;
>>>  }
>>>  
>>> +DEFINE_I440FX_MACHINE(v2_9, "pc-i440fx-2.9", NULL,
>>> +                      pc_i440fx_2_9_machine_options);
>>> +
>>> +static void pc_i440fx_2_8_machine_options(MachineClass *m)
>>> +{
>>> +    pc_i440fx_2_9_machine_options(m);
>>> +    m->is_default = 0;
>>> +    m->alias = NULL;
>>> +    SET_MACHINE_COMPAT(m, PC_COMPAT_2_8);
>>> +}
>>> +
>>>  DEFINE_I440FX_MACHINE(v2_8, "pc-i440fx-2.8", NULL,
>>>                        pc_i440fx_2_8_machine_options);
>>>  
>>> @@ -451,8 +462,6 @@ DEFINE_I440FX_MACHINE(v2_8, "pc-i440fx-2.8", NULL,
>>>  static void pc_i440fx_2_7_machine_options(MachineClass *m)
>>>  {
>>>      pc_i440fx_2_8_machine_options(m);
>>> -    m->is_default = 0;
>>> -    m->alias = NULL;
>>>      SET_MACHINE_COMPAT(m, PC_COMPAT_2_7);
>>>  }
>>>  
>>> diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
>>> index d042fe0..dd792a8 100644
>>> --- a/hw/i386/pc_q35.c
>>> +++ b/hw/i386/pc_q35.c
>>> @@ -301,19 +301,28 @@ static void pc_q35_machine_options(MachineClass *m)
>>>      m->max_cpus = 288;
>>>  }
>>>  
>>> -static void pc_q35_2_8_machine_options(MachineClass *m)
>>> +static void pc_q35_2_9_machine_options(MachineClass *m)
>>>  {
>>>      pc_q35_machine_options(m);
>>>      m->alias = "q35";
>>>  }
>>>  
>>> +DEFINE_Q35_MACHINE(v2_9, "pc-q35-2.9", NULL,
>>> +                   pc_q35_2_9_machine_options);
>>> +
>>> +static void pc_q35_2_8_machine_options(MachineClass *m)
>>> +{
>>> +    pc_q35_2_9_machine_options(m);
>>> +    m->alias = NULL;
>>> +    SET_MACHINE_COMPAT(m, PC_COMPAT_2_8);
>>> +}
>>> +
>>>  DEFINE_Q35_MACHINE(v2_8, "pc-q35-2.8", NULL,
>>>                     pc_q35_2_8_machine_options);
>>>  
>>>  static void pc_q35_2_7_machine_options(MachineClass *m)
>>>  {
>>>      pc_q35_2_8_machine_options(m);
>>> -    m->alias = NULL;
>>>      m->max_cpus = 255;
>>>      SET_MACHINE_COMPAT(m, PC_COMPAT_2_7);
>>>  }
>>>
>>
>