Re: [Xen-devel] [PATCH v2 01/11] vt-d: fix the IOMMU flush issue

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 26.04.16 at 04:18, <quan.xu@xxxxxxxxx> wrote:
> On April 25, 2016 5:22 PM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>> >>> On 18.04.16 at 16:00, <quan.xu@xxxxxxxxx> wrote:
>> > --- a/xen/drivers/passthrough/vtd/iommu.c
>> > +++ b/xen/drivers/passthrough/vtd/iommu.c
>> > @@ -558,14 +558,16 @@ static void iommu_flush_all(void)
>> >      }
>> >  }
>> >
>> > -static void __intel_iommu_iotlb_flush(struct domain *d, unsigned long gfn,
>> > -        int dma_old_pte_present, unsigned int page_count)
>> > +static int iommu_flush_iotlb(struct domain *d, unsigned long gfn,
>> > +                             int dma_old_pte_present,
>> > +                             unsigned int page_count)
>> >  {
>> >      struct hvm_iommu *hd = domain_hvm_iommu(d);
>> >      struct acpi_drhd_unit *drhd;
>> >      struct iommu *iommu;
>> >      int flush_dev_iotlb;
>> >      int iommu_domid;
>> > +    int rc = 0;
>> 
>> Pointless initializer.
> 
> I am afraid not.
> In case I don't initialize 'rc', the compiler prints out  " error: 'rc' may 
> be used uninitialized in this function [-Werror=maybe-uninitialized]".

Looking at the patch again I can't see why that would be the case.
Are you certain this isn't a result of subsequent patches, IOW did
you try this with just this one patch applied? rc gets initialized in
both the if() and the else branches, and there's no label allowing
that initialization to be bypassed...

Jan


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