Re: [Xen-devel] [PATCH v14 3/3] iommu: add rmrr Xen command line option for extra rmrrs

[Venu Busireddy <venu.busireddy@xxxxxxxxxx>]

On Tue, Jan 24, 2017 at 01:46:44AM -0700, Jan Beulich wrote:
> >>> On 23.01.17 at 19:20, <venu.busireddy@xxxxxxxxxx> wrote:
> > +        overlap = false;
> > +        list_for_each_entry(rmrru, &acpi_rmrr_units, list)
> > +        {
> > +            if ( pfn_to_paddr(base) <= rmrru->end_address &&
> > +                 rmrru->base_address <= pfn_to_paddr(end) )
> 
> So this now looks correct as long as rmrru->base_address is
> page aligned (as required by the spec), which should be good
> enough for now (considering that we make this assumption
> elsewhere). Nevertheless it would have been nice if you had,
> following the subsequent discussion with Elena, accounted for
> spec violations here.
> 
> > +        rmrr->segment = seg;
> > +        rmrr->base_address = pfn_to_paddr(user_rmrrs[i].base_pfn);
> > +        /* Align the end_address to the end of the page */
> > +        rmrr->end_address = pfn_to_paddr(user_rmrrs[i].end_pfn) | 
> > ~PAGE_MASK_4K;
> 
> Hmm, Ive just checked - in my reply to Elena I had intentionally used
> PAGE_MASK here (and I recall correcting it from PAGE_MASK_4K).
> What has led you to use PAGE_MASK_4K here, when pfn_to_paddr()
> uses PAGE_SHIFT?

Elena suggested to use PAGE_MASK_4K because the functions in
drivers/passthrough/vtd/iommu.c (including rmrr_identity_mapping())
use the _4K. With the current assumptions, both will work.

If you would like me to change this to PAGE_MASK, I will do so before
committing. Please let me know.

> With this corrected (which can be done upon commit, but I'd first
> like to understand your reasoning):
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> And despite Kevin's ack being present here, in light of what I've
> said on the other patch - Kevin, please confirm your ack.
> 
> Jan
> 

Regards,

Venu

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