linux-kernel - [PATCH] mm: don't defer struct page initialization for Xen pv guests

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Date:   Fri, 16 Feb 2018 14:37:26 +0100
From:   Juergen Gross <jgross@...e.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        xen-devel@...ts.xenproject.org
Cc:     akpm@...ux-foundation.org, mhocko@...e.com,
        Juergen Gross <jgross@...e.com>, stable@...r.kernel.org
Subject: [PATCH] mm: don't defer struct page initialization for Xen pv guests

Commit f7f99100d8d95dbcf09e0216a143211e79418b9f ("mm: stop zeroing
memory during allocation in vmemmap") broke Xen pv domains in some
configurations, as the "Pinned" information in struct page of early
page tables could get lost.

Avoid this problem by not deferring struct page initialization when
running as Xen pv guest.

Cc: <stable@...r.kernel.org> #4.15
Signed-off-by: Juergen Gross <jgross@...e.com>
---
 mm/page_alloc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 81e18ceef579..681d504b9a40 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -347,6 +347,9 @@ static inline bool update_defer_init(pg_data_t *pgdat,
 	/* Always populate low zones for address-constrained allocations */
 	if (zone_end < pgdat_end_pfn(pgdat))
 		return true;
+	/* Xen PV domains need page structures early */
+	if (xen_pv_domain())
+		return true;
 	(*nr_initialised)++;
 	if ((*nr_initialised > pgdat->static_init_pgcnt) &&
 	    (pfn & (PAGES_PER_SECTION - 1)) == 0) {
-- 
2.13.6