linux-kernel - Re: [Xen-devel] [PATCH 13/13] xen: allow more than 512 GB of RAM for 64 bit pv-domains

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <54E4751F.4090005@citrix.com>
Date:	Wed, 18 Feb 2015 11:18:55 +0000
From:	David Vrabel <david.vrabel@...rix.com>
To:	Juergen Gross <jgross@...e.com>, <linux-kernel@...r.kernel.org>,
	<xen-devel@...ts.xensource.com>, <konrad.wilk@...cle.com>,
	<david.vrabel@...rix.com>, <boris.ostrovsky@...cle.com>
Subject: Re: [Xen-devel] [PATCH 13/13] xen: allow more than 512 GB of RAM
 for 64 bit pv-domains

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.

And

If max_pfn < 512G, populate 3-level p2m /unless/ toolstack indicates it
supports the linear p2m.

People using crash analysis tools that need the 3-level p2m can clamp
dom0 memory with the Xen command line option.  FWIW, the tool we use
doesn't need this.

David

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/