Re: [PATCH v2 08/11] libxl: Only map legacy PCI IRQs if they are supported

[Oleksandr Andrushchenko <Oleksandr_Andrushchenko@epam.com>]

On 25.09.21 03:06, Stefano Stabellini wrote:
> On Thu, 23 Sep 2021, Oleksandr Andrushchenko wrote:
>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>
>> 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@epam.com>
>> Cc: Ian Jackson <iwj@xenproject.org>
>> Cc: Juergen Gross <jgross@suse.com>
>>
>> ---
>> 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
> This patch is a lot better than the previous version, thanks!
>
> I think the usage of pci_supp_legacy_irq below is good and we can't do
> better than that.
>
> I wonder if there is a better way than the above to export
> CONFIG_PCI_SUPP_LEGACY_IRQ. Suggestions?

I see nothing bad doing it this way, maybe Ian or Juergen can tell

if this is acceptable?

>
>
>>   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)
>> +{
>> +#ifdef CONFIG_PCI_SUPP_LEGACY_IRQ
>> +    return true;
>> +#else
>> +    return false;
>> +#endif
>> +}
>> +
>>   static void pci_add_dm_done(libxl__egc *egc,
>>                               pci_add_state *pas,
>>                               int rc)
>> @@ -1434,6 +1443,8 @@ static void pci_add_dm_done(libxl__egc *egc,
>>           }
>>       }
>>       fclose(f);
>> +    if (!pci_supp_legacy_irq())
>> +        goto out_no_irq;
>>       sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/irq", pci->domain,
>>                                   pci->bus, pci->dev, pci->func);
>>       f = fopen(sysfs_path, "r");
>> @@ -1983,6 +1994,8 @@ static void do_pci_remove(libxl__egc *egc, pci_remove_state *prs)
>>           }
>>           fclose(f);
>>   skip1:
>> +        if (!pci_supp_legacy_irq())
>> +            goto skip_irq;
>>           sysfs_path = GCSPRINTF(SYSFS_PCI_DEV"/"PCI_BDF"/irq", pci->domain,
>>                                  pci->bus, pci->dev, pci->func);
>>           f = fopen(sysfs_path, "r");
>> -- 
>> 2.25.1
>>