On 03/09/2015 10:10 AM, David Vrabel wrote:
Memory hotplug doesn't work with PV guests because:a) The p2m cannot be expanded to cover the new sections. b) add_memory() builds page tables for the new sections which means the new pages must have valid p2m entries (or a BUG occurs).
Is this due to recent p2m rework? -boris
So, in PV guests, clamp the target to the current (== maximum) number of pages and do not try to hotplug any memory. Signed-off-by: David Vrabel <david.vra...@citrix.com> --- Cc: Daniel Kiper <daniel.ki...@oracle.com> --- drivers/xen/balloon.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c index 0b52d92..4158196 100644 --- a/drivers/xen/balloon.c +++ b/drivers/xen/balloon.c @@ -225,6 +225,19 @@ static enum bp_state reserve_additional_memory(long credit) u64 hotplug_start_paddr; unsigned long balloon_hotplug = credit;+ /*+ * Memory hotplug doesn't work with PV guests because: + * + * a) The p2m cannot be expanded to cover the new sections. + * + * b) add_memory() builds page tables for the new sections + * which means they must be fully populated in advance. + */ + if (xen_pv_domain()) { + balloon_stats.target_pages = balloon_stats.current_pages; + return BP_DONE; + } + hotplug_start_paddr = PFN_PHYS(SECTION_ALIGN_UP(max_pfn)); balloon_hotplug = round_up(balloon_hotplug, PAGES_PER_SECTION); nid = memory_add_physaddr_to_nid(hotplug_start_paddr);
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