[Xen-devel] [PATCH 09 of 26 V3] libxl: drop 8M slack for PV guests

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

# HG changeset patch
# User Ian Campbell <ian.campbell@xxxxxxxxxx>
# Date 1330000276 0
# Node ID 4126474b72b57433538374ece5da684f594217a1
# Parent  773115e7c26a0ef77b1a8737361b51460515997a
libxl: drop 8M slack for PV guests.

This serves no purpose. It relates to the old 8M to "account for backend
allocations" which we used to add. This leaves a bit of unpopulated space in
the Pseudo-physical address space which can be used by backends when mapping
foreign memory. However 8M is not representative of that any more and modern
kernels do not operate in this way anyway.

I suspect an argument could be made for removing this from the libxl API
altogether but instead lets just set the overhead to 0.

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

diff -r 773115e7c26a -r 4126474b72b5 tools/libxl/libxl_create.c
--- a/tools/libxl/libxl_create.c        Thu Feb 23 12:31:16 2012 +0000
+++ b/tools/libxl/libxl_create.c        Thu Feb 23 12:31:16 2012 +0000
@@ -107,7 +107,7 @@ void libxl_domain_build_info_init(libxl_
         b_info->u.hvm.xen_platform_pci = 1;
         break;
     case LIBXL_DOMAIN_TYPE_PV:
-        b_info->u.pv.slack_memkb = 8 * 1024;
+        b_info->u.pv.slack_memkb = 0;
         break;
     default:
         abort();

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