Re: [PATCH v5 07/10] libxl: Only map legacy PCI IRQs if they are supported

[Oleksandr Andrushchenko <Oleksandr_Andrushchenko@xxxxxxxx>]

Hi, Roger!

On 25.10.21 16:22, Roger Pau Monné wrote:
> On Fri, Oct 08, 2021 at 08:55:32AM +0300, Oleksandr Andrushchenko wrote:
>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
>>
>> Arm's PCI passthrough implementation doesn't support legacy interrupts,
>> but MSI/MSI-X. This can be the case for other platforms too.
>> For that reason introduce a new CONFIG_PCI_SUPP_LEGACY_IRQ and add
>> it to the CFLAGS and compile the relevant code in the toolstack only if
>> applicable.
>>
>> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
>> Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>> Reviewed-by: Rahul Singh <rahul.singh@xxxxxxx>
>> Tested-by: Rahul Singh <rahul.singh@xxxxxxx>
>> ---
>> Cc: Ian Jackson <iwj@xxxxxxxxxxxxxx>
>> Cc: Juergen Gross <jgross@xxxxxxxx>
>>
>> Since v1:
>>   - Minimized #idefery by introducing pci_supp_legacy_irq function
>>     for relevant checks
>> ---
>>   tools/libs/light/Makefile    |  4 ++++
>>   tools/libs/light/libxl_pci.c | 13 +++++++++++++
>>   2 files changed, 17 insertions(+)
>>
>> diff --git a/tools/libs/light/Makefile b/tools/libs/light/Makefile
>> index 7d8c51d49242..bd3f6be2a183 100644
>> --- a/tools/libs/light/Makefile
>> +++ b/tools/libs/light/Makefile
>> @@ -46,6 +46,10 @@ CFLAGS += -Wno-format-zero-length -Wmissing-declarations \
>>      -Wno-declaration-after-statement -Wformat-nonliteral
>>   CFLAGS += -I.
>>   
>> +ifeq ($(CONFIG_X86),y)
>> +CFLAGS += -DCONFIG_PCI_SUPP_LEGACY_IRQ
>> +endif
> TBH, since CONFIG_PCI_SUPP_LEGACY_IRQ is used in a single place in the
> source I would consider just using CONFIG_X86, as I think it would be
> clear enough that some arches support legacy interrupt while others
> don't. Not sure it's worth going through the obfuscation of defining a
> separate one.
The idea behind not using CONFIG_X86 is to be arch agnostic,
so CONFIG_PCI_SUPP_LEGACY_IRQ makes more sense with this
respect
>> +
>>   SRCS-$(CONFIG_X86) += libxl_cpuid.c
>>   SRCS-$(CONFIG_X86) += libxl_x86.c
>>   SRCS-$(CONFIG_X86) += libxl_psr.c
>> diff --git a/tools/libs/light/libxl_pci.c b/tools/libs/light/libxl_pci.c
>> index 59f3686fc85e..4c2d7aeefbb2 100644
>> --- a/tools/libs/light/libxl_pci.c
>> +++ b/tools/libs/light/libxl_pci.c
>> @@ -1364,6 +1364,15 @@ static void pci_add_timeout(libxl__egc *egc, 
>> libxl__ev_time *ev,
>>       pci_add_dm_done(egc, pas, rc);
>>   }
>>   
>> +static bool pci_supp_legacy_irq(void)
> A naming more inline with the PCI specification (since we insisted on
> using ECAM instead of MCFG) would be intx, ie: pci_supports_intx.
This will require a follow up patch if we all agree this change is needed.
@Jan, are you ok with the rename?
>
> Thanks, Roger.
Thank you,
Oleksandr