Re: [PATCH v5 8/8] hw/mem/cxl_type3: Add CXL RAS Error Injection Support.

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 23/2/23 15:27, Jonathan Cameron wrote:
> On Thu, 23 Feb 2023 08:37:46 +0100
> Markus Armbruster <armbru@redhat.com> wrote:
> 
>> Thomas Huth <thuth@redhat.com> writes:
>>
>>> On 22/02/2023 19.16, Philippe Mathieu-Daudé wrote:
>>>> +Thomas (meson) & Marc-André (conditional QAPI)
>>>
>>> + Markus
>>>   
>>>> On 22/2/23 17:49, Jonathan Cameron wrote:
>>
>> [...]
>>
>>>>>>>> Doesn't these need
>>>>>>>>
>>>>>>>>          'if': 'CONFIG_CXL_MEM_DEVICE',
>>>>>>>>
>>>>>>>> ?
>>>>>>>
>>>>>>> If I make this change I get a bunch of
>>>>>>>
>>>>>>> ./qapi/qapi-types-cxl.h:18:13: error: attempt to use poisoned "CONFIG_CXL_MEM_DEVICE"
>>>>>>>       18 | #if defined(CONFIG_CXL_MEM_DEVICE)
>>>>>>
>>>>>> Err, I meant the generic CONFIG_CXL, not CONFIG_CXL_MEM_DEVICE.
>>>>>>   
>>>>>>> It's a target specific define (I think) as built alongside PCI_EXPRESS
>>>>>>> Only CXL_ACPI is specifically included by x86 and arm64 (out of tree)
>>>>>>>
>>>>>>> To be honest though I don't fully understand the QEMU build system so the reason
>>>>>>> for the error might be wrong.
>>>>>>
>>>>>> You need to restrict to system emulation (the 'have_system' check):
>>>>>
>>>>> This doesn't help - still have
>>>>> attempt to used poisoned "CONFIG_CXL"
>>>
>>> Not sure how the QAPI generator works, but target specific config switches can only be used in target specific json files there, so that's machine-target.json and misc-target.json currently, as far as I know. Not sure how the QAPI generator distinguishes between common and target specific code, though ... just by the "-target" suffix? Maybe Markus or Marc-André can comment on that.
>>
>> Whenever you use a poisoned macro in a conditional, all the code
>> generated for this .json file (we call it a "QAPI schema module")
>> becomes target-dependent.  The QAPI code generator itself is blissfully
>> unaware of this.
>>
>> Since target-dependent code needs to be compiled differently, the build
>> process needs to be know which modules are target-dependent.  We do this
>> in one of the stupidest ways that could possibly work: a module is
>> target-dependent if its name ends with "-target".  There are just two
>> right now: qapi/machine-target.json and qapi/misc-target.json.
>>
>> The logic resides in qapi/meson.build.  Look for
>>
>>      if module.endswith('-target')
> 
> Thanks for all the pointers.
>>
>> Questions?
> 
> Is it sensible to make the cxl stuff all target dependent and do the following?
> I like that we can get rid of the stubs if we do this but I'm sure there are
> disadvantages. Only alternative I can currently see is continue to have
> stubs and not make the qmp commands conditional on them doing anything useful.

I still don't understand what is the target-dependent part of CXL.

IIUC CXL depends on PCIe which isn't target dependent.