Re: [Xen-devel] [v6][PATCH 2/2] xen:vtd: missing RMRR mapping while share EPT

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Friday, August 01, 2014 6:47 AM
> 
> >>> On 01.08.14 at 11:50, <tiejun.chen@xxxxxxxxx> wrote:
> > On 2014/8/1 15:21, Jan Beulich wrote:
> >>>>> On 01.08.14 at 09:10, <tiejun.chen@xxxxxxxxx> wrote:
> >>> On 2014/8/1 14:51, Jan Beulich wrote:
> >>>>>>> On 31.07.14 at 11:45, <tiejun.chen@xxxxxxxxx> wrote:
> >>>>> Additionally, I'm trying to figure out that solution. As I mentioned
> >>>>> previously, I think we can reserve all RMRR once when a guest call
> >>>>> XENMEM_machine_memory_map to create its own memory. What
> about this
> >>>>> idea? Or other better suggestions?
> >>>>
> >>>> I don't think any HVM guest would ever call this, even more so that
> >>>> the call is restricted to Dom0. The reservation needs to be done
> >>>
> >>> Thanks for your correction. Actually I'm also afraid I may not find a
> >>> correct place where I want to go indeed since I'm not familiar this
> >>> process.
> >>>
> >>>> when guest memory gets populated (and its E820 constructed).
> >>>
> >>> Could you hint me where this action is covered?
> >>
> >> Memory population happens in tools/libxc/xc_hvm_build.c:setup_guest(),
> >> the E820 for the guest gets constructed in hvmloader (just grep for
> >> [eE]820).
> >>
> >
> > Thanks for your information.
> >
> > With further looking into this, instead of XENMEM_machine_memory_map,
> I
> > think we can go XENMEM_set_memory_map path, right?
> 
> I'm not sure - this may be an additional piece to be done for
> consistency (if the domain builder doesn't already call this), but
> since hvmloader doesn't appear to call XENMEM_memory_map it
> won't do on its own I'm afraid.
> 

I think we need expose RMRR to libxc so it can avoid allocating memory pages
conflicting to RMRR ranges, and then to hvmloader so it can avoid allocating
MMIO BAR conflicting to RMRR ranges and may further reserve those ranges
from guest e820 table, regardless of whether there is a device being assigned.

Thanks
Kevin

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