[PATCH v9 28/46] x86, mm: Add pointer about Xen mmu requirement for alloc_low_pages

[Yinghai Lu]

From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

Add link for more information
	279b706 x86,xen: introduce x86_init.mapping.pagetable_reserve

-v2: updated to commets from hpa to include commit name.

Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 arch/x86/mm/init.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index daff14c..a8e6d07 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -25,6 +25,15 @@ unsigned long __meminitdata pgt_buf_top;
 
 static unsigned long min_pfn_mapped;
 
+/*
+ * Pages returned are already directly mapped.
+ *
+ * Changing that is likely to break Xen, see commit:
+ *
+ *    279b706 x86,xen: introduce x86_init.mapping.pagetable_reserve
+ *
+ * for detailed information.
+ */
 __ref void *alloc_low_pages(unsigned int num)
 {
 	unsigned long pfn;
-- 
1.7.7

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