Commit 633d6f17 authored by Juergen Gross's avatar Juergen Gross Committed by David Vrabel
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x86/xen: prepare p2m list for memory hotplug

Commit 054954eb

 ("xen: switch to linear
virtual mapped sparse p2m list") introduced a regression regarding to
memory hotplug for a pv-domain: as the virtual space for the p2m list
is allocated for the to be expected memory size of the domain only,
hotplugged memory above that size will not be usable by the domain.

Correct this by using a configurable size for the p2m list in case of
memory hotplug enabled (default supported memory size is 512 GB for
64 bit domains and 4 GB for 32 bit domains).
Signed-off-by: default avatarJuergen Gross <>
Cc: <> # 3.19+
Reviewed-by: default avatarDaniel Kiper <>
Signed-off-by: default avatarDavid Vrabel <>
parent af6fc858
......@@ -91,6 +91,12 @@ EXPORT_SYMBOL_GPL(xen_p2m_size);
unsigned long xen_max_p2m_pfn __read_mostly;
#define P2M_LIMIT 0
static DEFINE_SPINLOCK(p2m_update_lock);
static unsigned long *p2m_mid_missing_mfn;
......@@ -385,9 +391,11 @@ static void __init xen_rebuild_p2m_list(unsigned long *p2m)
void __init xen_vmalloc_p2m_tree(void)
static struct vm_struct vm;
unsigned long p2m_limit;
p2m_limit = (phys_addr_t)P2M_LIMIT * 1024 * 1024 * 1024 / PAGE_SIZE;
vm.flags = VM_ALLOC;
vm.size = ALIGN(sizeof(unsigned long) * xen_max_p2m_pfn,
vm.size = ALIGN(sizeof(unsigned long) * max(xen_max_p2m_pfn, p2m_limit),
vm_area_register_early(&vm, PMD_SIZE * PMDS_PER_MID_PAGE);
pr_notice("p2m virtual area at %p, size is %lx\n", vm.addr, vm.size);
......@@ -55,6 +55,23 @@ config XEN_BALLOON_MEMORY_HOTPLUG
In that case step 3 should be omitted.
int "Hotplugged memory limit (in GiB) for a PV guest"
default 512 if X86_64
default 4 if X86_32
range 0 64 if X86_32
depends on XEN_HAVE_PVMMU
Maxmium amount of memory (in GiB) that a PV guest can be
expanded to when using memory hotplug.
A PV guest can have more memory than this limit if is
started with a larger maximum.
This value is used to allocate enough space in internal
tables needed for physical memory administration.
bool "Scrub pages before returning them to system"
depends on XEN_BALLOON
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