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authorIan Campbell <Ian.Campbell@citrix.com>2011-12-14 07:16:08 -0500
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2011-12-15 11:24:02 -0500
commitd3db728125c4470a2d061ac10fa7395e18237263 (patch)
treeedc316773dde8f7a7a7dfe7358d18cba1c369ab0 /arch/x86
parent99cb2ddcc617f43917e94a4147aa3ccdb2bcd77e (diff)
xen: only limit memory map to maximum reservation for domain 0.
d312ae878b6a "xen: use maximum reservation to limit amount of usable RAM" clamped the total amount of RAM to the current maximum reservation. This is correct for dom0 but is not correct for guest domains. In order to boot a guest "pre-ballooned" (e.g. with memory=1G but maxmem=2G) in order to allow for future memory expansion the guest must derive max_pfn from the e820 provided by the toolstack and not the current maximum reservation (which can reflect only the current maximum, not the guest lifetime max). The existing algorithm already behaves this correctly if we do not artificially limit the maximum number of pages for the guest case. For a guest booted with maxmem=512, memory=128 this results in: [ 0.000000] BIOS-provided physical RAM map: [ 0.000000] Xen: 0000000000000000 - 00000000000a0000 (usable) [ 0.000000] Xen: 00000000000a0000 - 0000000000100000 (reserved) -[ 0.000000] Xen: 0000000000100000 - 0000000008100000 (usable) -[ 0.000000] Xen: 0000000008100000 - 0000000020800000 (unusable) +[ 0.000000] Xen: 0000000000100000 - 0000000020800000 (usable) ... [ 0.000000] NX (Execute Disable) protection: active [ 0.000000] DMI not present or invalid. [ 0.000000] e820 update range: 0000000000000000 - 0000000000010000 (usable) ==> (reserved) [ 0.000000] e820 remove range: 00000000000a0000 - 0000000000100000 (usable) -[ 0.000000] last_pfn = 0x8100 max_arch_pfn = 0x1000000 +[ 0.000000] last_pfn = 0x20800 max_arch_pfn = 0x1000000 [ 0.000000] initial memory mapped : 0 - 027ff000 [ 0.000000] Base memory trampoline at [c009f000] 9f000 size 4096 -[ 0.000000] init_memory_mapping: 0000000000000000-0000000008100000 -[ 0.000000] 0000000000 - 0008100000 page 4k -[ 0.000000] kernel direct mapping tables up to 8100000 @ 27bb000-27ff000 +[ 0.000000] init_memory_mapping: 0000000000000000-0000000020800000 +[ 0.000000] 0000000000 - 0020800000 page 4k +[ 0.000000] kernel direct mapping tables up to 20800000 @ 26f8000-27ff000 [ 0.000000] xen: setting RW the range 27e8000 - 27ff000 [ 0.000000] 0MB HIGHMEM available. -[ 0.000000] 129MB LOWMEM available. -[ 0.000000] mapped low ram: 0 - 08100000 -[ 0.000000] low ram: 0 - 08100000 +[ 0.000000] 520MB LOWMEM available. +[ 0.000000] mapped low ram: 0 - 20800000 +[ 0.000000] low ram: 0 - 20800000 With this change "xl mem-set <domain> 512M" will successfully increase the guest RAM (by reducing the balloon). There is no change for dom0. Reported-and-Tested-by: George Shuklin <george.shuklin@gmail.com> Signed-off-by: Ian Campbell <ian.campbell@citrix.com> Cc: stable@kernel.org Reviewed-by: David Vrabel <david.vrabel@citrix.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/xen/setup.c18
1 files changed, 15 insertions, 3 deletions
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 38d0af4fefec..a54ff1aab6eb 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -173,9 +173,21 @@ static unsigned long __init xen_get_max_pages(void)
173 domid_t domid = DOMID_SELF; 173 domid_t domid = DOMID_SELF;
174 int ret; 174 int ret;
175 175
176 ret = HYPERVISOR_memory_op(XENMEM_maximum_reservation, &domid); 176 /*
177 if (ret > 0) 177 * For the initial domain we use the maximum reservation as
178 max_pages = ret; 178 * the maximum page.
179 *
180 * For guest domains the current maximum reservation reflects
181 * the current maximum rather than the static maximum. In this
182 * case the e820 map provided to us will cover the static
183 * maximum region.
184 */
185 if (xen_initial_domain()) {
186 ret = HYPERVISOR_memory_op(XENMEM_maximum_reservation, &domid);
187 if (ret > 0)
188 max_pages = ret;
189 }
190
179 return min(max_pages, MAX_DOMAIN_PAGES); 191 return min(max_pages, MAX_DOMAIN_PAGES);
180} 192}
181 193