Re: [Xen-devel] [PATCH v3 1/4] amd-iommu: add flush iommu_ops

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.12.18 at 13:58, <Paul.Durrant@xxxxxxxxxx> wrote:
>> From: Paul Durrant
>> Sent: 05 December 2018 12:57
>> 
>> > From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>> > Sent: 05 December 2018 11:46
>> >
>> > >>> On 05.12.18 at 12:29, <paul.durrant@xxxxxxxxxx> wrote:
>> > > --- a/xen/drivers/passthrough/amd/iommu_map.c
>> > > +++ b/xen/drivers/passthrough/amd/iommu_map.c
>> > > @@ -634,6 +634,56 @@ int amd_iommu_unmap_page(struct domain *d, dfn_t
>> > dfn)
>> > >      spin_unlock(&hd->arch.mapping_lock);
>> > >
>> > >      amd_iommu_flush_pages(d, dfn_x(dfn), 0);
>> > > +    return 0;
>> > > +}
>> > > +
>> > > +static unsigned long flush_count(unsigned long dfn, unsigned int
>> > page_count,
>> > > +                                 unsigned int order)
>> > > +{
>> > > +    unsigned long start = dfn >> order;
>> > > +    unsigned long end = (dfn + page_count - 1) >> 1;
>> >
>> > Granted in my earlier reply I had a missing opening parenthesis,
>> > but the above is pretty clearly the wrong way of addressing
>> > the resulting build error.
>> 
>> Sorry, that's way too cryptic. What build error?
> 
> I agree there is a typo there, in that the '>> 1' should be '>> order'... Is 
> that what you're getting at?

In the reply to v2 I did suggest

    unsigned long start = dfn >> order;
    unsigned long end = (dfn + page_count - 1) >> order) + 1;

which of course needs to be

    unsigned long start = dfn >> order;
    unsigned long end = ((dfn + page_count - 1) >> order) + 1;

whereas I was guessing that you might have noticed the build
error with the original suggestion, but then wrongly dropped the
"order) + " part.

Jan



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