From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [PATCH 13/13] xen: allow more than 512 GB of RAM for 64 bit pv-domains Date: Thu, 19 Feb 2015 17:51:48 +0000 Message-ID: <54E622B4.7080701@cantab.net> References: <1424242326-26611-1-git-send-email-jgross@suse.com> <1424242326-26611-14-git-send-email-jgross@suse.com> <54E4751F.4090005@citrix.com> <54E47CD2.5000702@suse.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <54E47CD2.5000702@suse.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Juergen Gross , xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On 18/02/2015 11:51, Juergen Gross wrote: > On 02/18/2015 12:18 PM, David Vrabel wrote: >> On 18/02/15 06:52, Juergen Gross wrote: >>> >>> +if X86_64 >>> +choice >>> + prompt "Support pv-domains larger than 512GB" >>> + default XEN_512GB_NONE >>> + help >>> + Support paravirtualized domains with more than 512GB of RAM. >>> + >>> + The Xen tools and crash dump analysis tools might not support >>> + pv-domains with more than 512 GB of RAM. This option controls the >>> + default setting of the kernel to use only up to 512 GB or more. >>> + It is always possible to change the default via specifying the >>> + boot parameter "xen_512gb_limit". >>> + >>> + config XEN_512GB_NONE >>> + bool "neither dom0 nor domUs can be larger than 512GB" >>> + config XEN_512GB_DOM0 >>> + bool "dom0 can be larger than 512GB, domUs not" >>> + config XEN_512GB_DOMU >>> + bool "domUs can be larger than 512GB, dom0 not" >>> + config XEN_512GB_ALL >>> + bool "dom0 and domUs can be larger than 512GB" >>> +endchoice >>> +endif >> >> This configuration option doesn't look useful to me. Can we get rid of >> it with runtime checking. e.g., >> >> If dom0, enable >512G. >> If domU, enable >512G if requested by command line option /or/ toolstack >> indicates that it supports the linear p2m. > > How is the toolstack supposed to indicate this? I don't know. A bit in the shared info perhaps? > I'd be more than happy to get rid of that option. For Dom0 you seem to > have changed your mind (you rejected enabling >512GB as default last > year). Since for dom0 it's only crash analysis that might be impacted, removing the option is fine. Anyone using such a tool probably know what they're doing. > Doing some more tests I found the command line option is problematic: > The option seems to be evaluated only after it is needed (I did the > first tests using the config option). Can we get rid of the option > even for domU? Or do I have to pre-scan the command line for the option? I don't what people to be able to inadvertantly create domUs that cannot be saved/migrated. Can you think of another mechanism? >> And >> >> If max_pfn < 512G, populate 3-level p2m /unless/ toolstack indicates it >> supports the linear p2m. > > What about Dom0? This bit is for dom0 and domU. David