Re: [Xen-devel] [PATCH v11 2/3] Differentiate IO/mem resources tracked by ioreq server

["Yu, Zhang" <yu.c.zhang@xxxxxxxxxxxxxxx>]

On 1/22/2016 7:43 PM, Jan Beulich wrote:
> > > > On 22.01.16 at 04:20, <yu.c.zhang@xxxxxxxxxxxxxxx> wrote:
> > @@ -2601,6 +2605,16 @@ struct hvm_ioreq_server *hvm_select_ioreq_server(struct 
> > domain *d,
> >           type = (p->type == IOREQ_TYPE_PIO) ?
> >                   HVMOP_IO_RANGE_PORT : HVMOP_IO_RANGE_MEMORY;
> >           addr = p->addr;
> > +        if ( type == HVMOP_IO_RANGE_MEMORY )
> > +        {
> > +             ram_page = get_page_from_gfn(d, p->addr >> PAGE_SHIFT,
> > +                                          &p2mt, P2M_UNSHARE);
> It seems to me like I had asked before: Why P2M_UNSHARE instead
> of just P2M_QUERY? (This could surely be fixed up while committing,
> the more that I've already done some cleanup here, but I'd like to
> understand this before it goes in.)
Hah, sorry for my bad memory. :)
I did not found P2M_QUERY; only P2M_UNSHARE and P2M_ALLOC are
defined. But after reading the code in ept_get_entry(), I guess the
P2M_UNSHARE is not accurate, maybe I should use 0 here for the
p2m_query_t parameter in get_page_from_gfn()?

> > +             if ( p2mt == p2m_mmio_write_dm )
> > +                 type = HVMOP_IO_RANGE_WP_MEM;
> > +
> > +             if ( ram_page )
> > +                 put_page(ram_page);
> > +        }
> >       }
> >
> >       list_for_each_entry ( s,
> > @@ -2642,6 +2656,11 @@ struct hvm_ioreq_server *hvm_select_ioreq_server(struct 
> > domain *d,
> >               }
> >
> >               break;
> > +        case HVMOP_IO_RANGE_WP_MEM:
> > +            if ( rangeset_contains_singleton(r, PFN_DOWN(addr)) )
> > +                return s;
> Considering you've got p2m_mmio_write_dm above - can this
> validly return false here?
Well, if we have multiple ioreq servers defined, it will...
Currently, this p2m type is only used in XenGT, which has only one
ioreq server other than qemu for the vGPU. But suppose there will
be more devices using this type and more ioreq servers introduced
for them, it can return false.
> Jan
B.R.
Yu
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