Re: [Qemu-devel] [PATCH v5 5/5] nvdimm acpi: add _CRS

[Igor Mammedov]

On Thu, 3 Mar 2016 16:48:55 +0200
"Michael S. Tsirkin" <address@hidden> wrote:

> On Thu, Mar 03, 2016 at 10:05:31PM +0800, Xiao Guangrong wrote:
> > 
> > 
> > On 03/03/2016 09:29 PM, Michael S. Tsirkin wrote:  
> > >On Wed, Mar 02, 2016 at 07:50:41PM +0800, Xiao Guangrong wrote:  
> > >>As Igor suggested that we can report the BIOS patched operation region
> > >>so that OSPM could see that particular range is in use and be able to
> > >>notice conflicts if it happens some day
> > >>
> > >>Signed-off-by: Xiao Guangrong <address@hidden>  
> > >
> > >This is reserved RAM, exposing it in _CRS makes no sense to me.  
> > 
> > As more and more memory will be reserved by BIOS/QEMU, report the
> > information to OSPM and let it check the potential error is bad,
> > no? :)  
> 
> guest has enough info to detect conflicts if it wishes to.
> IIUC _CRS is not intended for RAM, it's for MMIO
> resources, if it works for RAM that's an accident.
If range isn't reserved here, then guest might assume that it's
free to use it for a PCI device since PCI0._CRS reports it
as available.
So we should either reserve range or punch a hole in PCI0._CRS.
Reserving ranges is simpler and that's what we've switched to
from manual hole punching, see PCI/CPU/Memory hotplug and other
motherboard resources.