Re: [Qemu-devel] [PATCH] pci: fix compilation warnings

[Marcel Apfelbaum <marcel@redhat.com>]

On 03/28/2016 11:43 AM, Stefan Weil wrote:
> Am 28.03.2016 um 09:23 schrieb Marcel Apfelbaum:
>> Fix 'error: shift exponent -1 is negative' warning
>> by adding a corresponding assert.
>>
>> Reported-by: Peter Maydell <peter.maydell@linaro.org>
>> Signed-off-by: Markus Armbruster <armbru@redhat.com>
>> Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
>> ---
>>   hw/pci/pci.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
>> index e67664d..a1d41aa 100644
>> --- a/hw/pci/pci.c
>> +++ b/hw/pci/pci.c
>> @@ -163,11 +163,15 @@ int pci_bar(PCIDevice *d, int reg)
>>
>>   static inline int pci_irq_state(PCIDevice *d, int irq_num)
>>   {
>> +    assert(irq_num >= 0);
>> +
>>   	return (d->irq_state >> irq_num) & 0x1;
>>   }
>>
>>   static inline void pci_set_irq_state(PCIDevice *d, int irq_num, int level)
>>   {
>> +    assert(irq_num >= 0);
>> +
>>   	d->irq_state &= ~(0x1 << irq_num);
>>   	d->irq_state |= level << irq_num;
>>   }
>
> Do we use negative values for irq_num anywhere?

Hi Stefan,

I didn't see any irq_nu assignments to a negative value but there are
some cases where it can be negative due to arithmetical operations like:

    hw/pci-host/bonito.c:651:    int internal_irq = irq_num - BONITO_IRQ_BASE;

On other cases we look for negative value:

    hw/ppc/ppc4xx_devs.c:171:    if (irq_num < 0 || irq_num > 3)
or
    hw/ppc/ppc4xx_pci.c:263:    if (irq_num < 0)


> If not, using an unsigned irq_num might be a better solution.

All of the above are manageable, of course, but we are close to
hard freeze (tomorrow) and the scope of this patch is much smaller (fix a compilation warning)

I think is definitely worth looking into it, but maybe as part of QEMU 2.7.

Thanks,
Marcel
>
> Stefan
>