# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1245317477 -3600
# Node ID 8440fc9f7a25fe4b35f82a3123c7a4145b54b721
# Parent 1c01814f9a25d1779773b240ac6ce96d41dc1af2
x86-64: do not pass unmanageable amounts of memory to Dom0
Due to address space restrictions it is not possible to successfully
pass more than about 500Gb to a Linux Dom0 unless its kernel specifies
a non-default phys-to-machine map location via XEN_ELFNOTE_INIT_P2M.
For non-Linux Dom0 kernels I can't say whether the limit could be set
to close to 1Tb, but since passing such huge amounts of memory isn't
very useful anyway (and can be enforced via dom0_mem=3D), the patch
doesn't attempt to guess the kernel type and restricts the memory
amount in all cases.
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
---
xen/arch/x86/domain_build.c | 79 ++++++++++++++++++++++++++++++++------------
1 files changed, 59 insertions(+), 20 deletions(-)
diff -r 1c01814f9a25 -r 8440fc9f7a25 xen/arch/x86/domain_build.c
--- a/xen/arch/x86/domain_build.c Thu Jun 18 10:30:28 2009 +0100
+++ b/xen/arch/x86/domain_build.c Thu Jun 18 10:31:17 2009 +0100
@@ -146,33 +146,65 @@ static struct page_info * __init alloc_c
return page;
}
-static unsigned long __init compute_dom0_nr_pages(void)
+static unsigned long __init compute_dom0_nr_pages(
+#ifdef __x86_64__
+ unsigned long vstart, unsigned long vend, size_t sizeof_long)
+#else
+ void)
+#endif
{
unsigned long avail = avail_domheap_pages() + initial_images_nrpages();
+ unsigned long nr_pages = dom0_nrpages;
+ unsigned long min_pages = dom0_min_nrpages;
+ unsigned long max_pages = dom0_max_nrpages;
/*
* If domain 0 allocation isn't specified, reserve 1/16th of available
* memory for things like DMA buffers. This reservation is clamped to
* a maximum of 128MB.
*/
- if ( dom0_nrpages == 0 )
- {
- dom0_nrpages = avail;
- dom0_nrpages = min(dom0_nrpages / 16, 128L << (20 - PAGE_SHIFT));
- dom0_nrpages = -dom0_nrpages;
- }
+ if ( nr_pages == 0 )
+ nr_pages = -min(avail / 16, 128UL << (20 - PAGE_SHIFT));
/* Negative memory specification means "all memory - specified amount". */
- if ( dom0_nrpages < 0 ) dom0_nrpages += avail;
- if ( dom0_min_nrpages < 0 ) dom0_min_nrpages += avail;
- if ( dom0_max_nrpages < 0 ) dom0_max_nrpages += avail;
+ if ( (long)nr_pages < 0 ) nr_pages += avail;
+ if ( (long)min_pages < 0 ) min_pages += avail;
+ if ( (long)max_pages < 0 ) max_pages += avail;
/* Clamp dom0 memory according to min/max limits and available memory. */
- dom0_nrpages = max(dom0_nrpages, dom0_min_nrpages);
- dom0_nrpages = min(dom0_nrpages, dom0_max_nrpages);
- dom0_nrpages = min(dom0_nrpages, (long)avail);
-
- return dom0_nrpages;
+ nr_pages = max(nr_pages, min_pages);
+ nr_pages = min(nr_pages, max_pages);
+ nr_pages = min(nr_pages, avail);
+
+#ifdef __x86_64__
+ if ( vstart && dom0_nrpages <= 0 &&
+ (dom0_min_nrpages <= 0 || nr_pages > min_pages) )
+ {
+ /*
+ * Legacy Linux kernels (i.e. such without a XEN_ELFNOTE_INIT_P2M
+ * note) require that there is enough virtual space beyond the initial
+ * allocation to set up their initial page tables. This space is
+ * roughly the same size as the p2m table, so make sure the initial
+ * allocation doesn't consume more than about half the space that's
+ * available between params.virt_base and the address space end.
+ */
+ unsigned long end = vend + nr_pages * sizeof_long;
+
+ if ( end > vstart )
+ end += end - vstart;
+ if ( end <= vstart ||
+ (sizeof_long < sizeof(end) && end > (1UL << (8 * sizeof_long))) )
+ {
+ end = sizeof_long >= sizeof(end) ? 0 : 1UL << (8 * sizeof_long);
+ nr_pages = (end - vend) / (2 * sizeof_long);
+ if ( dom0_min_nrpages > 0 && nr_pages < min_pages )
+ nr_pages = min_pages;
+ printk("Dom0 memory clipped to %lu pages\n", nr_pages);
+ }
+ }
+#endif
+
+ return nr_pages;
}
static void __init process_dom0_ioports_disable(void)
@@ -282,8 +314,6 @@ int __init construct_dom0(
d->max_pages = ~0U;
- nr_pages = compute_dom0_nr_pages();
-
if ( (rc = bzimage_parse(image_base, &image_start, &image_len)) != 0 )
return rc;
@@ -342,9 +372,18 @@ int __init construct_dom0(
d->arch.is_32bit_pv = d->arch.has_32bit_shinfo = 1;
v->vcpu_info = (void *)&d->shared_info->compat.vcpu_info[0];
- if ( nr_pages != (unsigned int)nr_pages )
- nr_pages = UINT_MAX;
- }
+ nr_pages = compute_dom0_nr_pages(parms.virt_base,
+ round_pgup(parms.virt_kend) + round_pgup(initrd_len),
+ sizeof(unsigned int));
+ }
+ else if (parms.p2m_base != UNSET_ADDR)
+ nr_pages = compute_dom0_nr_pages(0, 0, 0);
+ else
+ nr_pages = compute_dom0_nr_pages(parms.virt_base,
+ round_pgup(parms.virt_kend) + round_pgup(initrd_len),
+ sizeof(unsigned long));
+#else
+ nr_pages = compute_dom0_nr_pages();
#endif
if ( parms.pae == PAEKERN_extended_cr3 )
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