Re: [RFC][PATCH 04/13] tools/libxl: detect and avoid conflicts with RDM

From: "Tian, Kevin" <kevin.tian@intel.com>
To: Ian Jackson <Ian.Jackson@eu.citrix.com>,
	"Chen, Tiejun" <tiejun.chen@intel.com>
Cc: "wei.liu2@citrix.com" <wei.liu2@citrix.com>,
	"ian.campbell@citrix.com" <ian.campbell@citrix.com>,
	"andrew.cooper3@citrix.com" <andrew.cooper3@citrix.com>,
	"tim@xen.org" <tim@xen.org>,
	"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
	"stefano.stabellini@citrix.com" <stefano.stabellini@citrix.com>,
	"JBeulich@suse.com" <JBeulich@suse.com>,
	"Zhang, Yang Z" <yang.z.zhang@intel.com>
Subject: Re: [RFC][PATCH 04/13] tools/libxl: detect and avoid conflicts with RDM
Date: Wed, 15 Apr 2015 18:22:24 +0000	[thread overview]
Message-ID: <AADFC41AFE54684AB9EE6CBC0274A5D12620DF4A@SHSMSX101.ccr.corp.intel.com> (raw)
In-Reply-To: <21806.25404.276583.454770@mariner.uk.xensource.com>

> From: Ian Jackson [mailto:Ian.Jackson@eu.citrix.com]
> Sent: Wednesday, April 15, 2015 9:10 PM
> 
> Tiejun Chen writes ("[RFC][PATCH 04/13] tools/libxl: detect and avoid conflicts
> with RDM"):
> > While building a VM, HVM domain builder provides struct hvm_info_table{}
> > to help hvmloader. Currently it includes two fields to construct guest
> > e820 table by hvmloader, low_mem_pgend and high_mem_pgend. So we
> should
> > check them to fix any conflict with RAM.
> 
> I'm not really qualified to understand all of this, because I'm not an
> x86 expert - I don't even know what RDM is.  But this does all seem
> very complicated.  Can I have a second opinion from an x86 expert ?

[Patch 00/13] provides some background for necessary changes. In a nutshell,
the goal is to reserve ACPI reported reserved memory (through RMRR table,
but renamed to Reserved Device Memory (RDM) as a general user space
term here) in gfn space. There are various options to do reservation and 
handle potential conflicts, and based on long discussion people agreed that 
putting that logic centrally in libxl looks a cleaner way to go. That's why this 
patch is a bit complex being a core logic of this patch set. I'd expect other 
maintainers to also review this part carefully.

Thanks
Kevin