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Date: Mon, 7 Mar 2016 14:22:38 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v5 5/5] nvdimm acpi: add _CRS
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To: Igor Mammedov <imammedo@redhat.com>
Cc: Xiao Guangrong <guangrong.xiao@linux.intel.com>, ehabkost@redhat.com, kvm@vger.kernel.org, gleb@kernel.org, mtosatti@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com, pbonzini@redhat.com, dan.j.williams@intel.com, rth@twiddle.net

On Mon, Mar 07, 2016 at 01:16:48PM +0100, Igor Mammedov wrote:
> On Thu, 3 Mar 2016 16:48:55 +0200
> "Michael S. Tsirkin" <mst@redhat.com> 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 <guangrong.xiao@linux.intel.com>  
> > > >
> > > >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.

Does it really? I thought it's guest RAM allocated by BIOS, as opposed
to PCI memory. Am I wrong?

> 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.