path: root/Documentation/kernel-parameters.txt
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authorJuergen Gross <jgross@suse.com>2015-07-17 06:51:36 +0200
committerDavid Vrabel <david.vrabel@citrix.com>2015-08-20 12:24:24 +0100
commitc70727a5bc18a5a233fddc6056d1de9144d7a293 (patch)
tree98c09e90e78f0d3bb79be2592e3bed5e5c847f83 /Documentation/kernel-parameters.txt
parent70e61199559a09c62714694cd5ac3c3640c41552 (diff)
xen: allow more than 512 GB of RAM for 64 bit pv-domains
64 bit pv-domains under Xen are limited to 512 GB of RAM today. The main reason has been the 3 level p2m tree, which was replaced by the virtual mapped linear p2m list. Parallel to the p2m list which is being used by the kernel itself there is a 3 level mfn tree for usage by the Xen tools and eventually for crash dump analysis. For this tree the linear p2m list can serve as a replacement, too. As the kernel can't know whether the tools are capable of dealing with the p2m list instead of the mfn tree, the limit of 512 GB can't be dropped in all cases. This patch replaces the hard limit by a kernel parameter which tells the kernel to obey the 512 GB limit or not. The default is selected by a configuration parameter which specifies whether the 512 GB limit should be active per default for domUs (domain save/restore/migration and crash dump analysis are affected). Memory above the domain limit is returned to the hypervisor instead of being identity mapped, which was wrong anyway. The kernel configuration parameter to specify the maximum size of a domain can be deleted, as it is not relevant any more. Signed-off-by: Juergen Gross <jgross@suse.com> Acked-by: Konrad Rzeszutek Wilk <Konrad.wilk@oracle.com> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Diffstat (limited to 'Documentation/kernel-parameters.txt')
1 files changed, 7 insertions, 0 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 1d6f0459cd7b..47f7b985f833 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -4078,6 +4078,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
plus one apbt timer for broadcast timer.
x86_intel_mid_timer=apbt_only | lapic_and_apbt
+ xen_512gb_limit [KNL,X86-64,XEN]
+ Restricts the kernel running paravirtualized under Xen
+ to use only up to 512 GB of RAM. The reason to do so is
+ crash analysis tools and Xen tools for doing domain
+ save/restore/migration must be enabled to handle larger
+ domains.
xen_emul_unplug= [HW,X86,XEN]
Unplug Xen emulated devices
Format: [unplug0,][unplug1]

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