.breaks one of my boxes (Core i3-2100), with Xen 4.1.1 (with and w/out the
23790 changset in it).
I've traced it down to the fact that I booted my dom0 without
dom0_mem=X flag with a machine that has more than 8GB. Weirdly enough
I can only reproduce this under Intel boxes.
Anyhow this patch fixes it for me.
commit e4297f5719e982d95788cd53e284a7a389eedb45
Author: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Date: Mon Sep 12 15:58:25 2011 -0400
xen/e820: if there is not dom0_mem, don't tweak extra_pages.
The patch "xen: use maximum reservation to limit amount of usable RAM"
(d312ae878b6aed3912e1acaaf5d0b2a9d08a4f11) breaks machines that
do not use 'dom0_mem=' argument with:
reserve RAM buffer: 000000133f2e2000 - 000000133fffffff
(XEN) mm.c:4976:d0 Global bit is set to kernel page fffff8117e
(XEN) domain_crash_sync called from entry.S
(XEN) Domain 0 (vcpu#0) crashed on cpu#0:
...
The reason being that the last E820 entry is created using the
'extra_pages' (which is based on how many pages have been freed).
The mentioned git commit sets the initial value of 'extra_pages'
using a hypercall which returns the number of pages (if dom0_mem
has been used) or -1 otherwise. If the later we return with
MAX_DOMAIN_PAGES as basis for calculation:
return min(max_pages, MAX_DOMAIN_PAGES);
and use it:
extra_limit = xen_get_max_pages();
if (extra_limit >= max_pfn)
extra_pages = extra_limit - max_pfn;
else
extra_pages = 0;
which means we end up with extra_pages = 128GB in PFNs (33554432)
- 8GB in PFNs (2097152, on this specific box, can be larger or smaller),
and then we add that value to the E820 making it:
Xen: 00000000ff000000 - 0000000100000000 (reserved)
Xen: 0000000100000000 - 000000133f2e2000 (usable)
which is clearly wrong. It should look as so:
Xen: 00000000ff000000 - 0000000100000000 (reserved)
Xen: 0000000100000000 - 000000027fbda000 (usable)
Naturally this problem does not present itself if dom0_mem=max:X
is used.
CC: David Vrabel <david.vrabel@xxxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index c3b8d44..0632de1 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -185,16 +185,18 @@ static unsigned long __init xen_set_identity(const struct
e820entry *list,
return identity;
}
-static unsigned long __init xen_get_max_pages(void)
+static bool __init xen_get_max_pages(unsigned long *max_pages)
{
- unsigned long max_pages = MAX_DOMAIN_PAGES;
domid_t domid = DOMID_SELF;
int ret;
ret = HYPERVISOR_memory_op(XENMEM_maximum_reservation, &domid);
- if (ret > 0)
- max_pages = ret;
- return min(max_pages, MAX_DOMAIN_PAGES);
+ /* If dom0_mem=X is not used, it will return -1. */
+ if (ret > 0) {
+ *max_pages = (unsigned long)min(ret, MAX_DOMAIN_PAGES);
+ return true;
+ }
+ return false;
}
/**
@@ -210,7 +212,7 @@ char * __init xen_memory_setup(void)
int rc;
struct xen_memory_map memmap;
unsigned long extra_pages = 0;
- unsigned long extra_limit;
+ unsigned long extra_limit = 0;
unsigned long identity_pages = 0;
int i;
int op;
@@ -305,11 +307,12 @@ char * __init xen_memory_setup(void)
sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
- extra_limit = xen_get_max_pages();
- if (extra_limit >= max_pfn)
- extra_pages = extra_limit - max_pfn;
- else
- extra_pages = 0;
+ if (xen_get_max_pages(&extra_limit)) {
+ if (extra_limit >= max_pfn)
+ extra_pages = extra_limit - max_pfn;
+ else
+ extra_pages = 0;
+ }
extra_pages += xen_return_unused_memory(xen_start_info->nr_pages,
&e820);
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