linux-kernel - [PATCH] xen: Don't try to call xen_alloc_p2m

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Date:   Wed, 23 Aug 2017 18:27:04 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     jgross@...e.com
Cc:     xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: [PATCH] xen: Don't try to call xen_alloc_p2m_entry() on autotranslating guests

Commit aba831a69632 ("xen: remove tests for pvh mode in pure pv paths")
removed XENFEAT_auto_translated_physmap test in xen_alloc_p2m_entry()
since it is assumed that the routine is never called by non-PV guests.

However, alloc_xenballooned_pages() may make this call on a PVH guest.
Prevent this from happening by adding XENFEAT_auto_translated_physmap
check there.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Fixes: aba831a69632 ("xen: remove tests for pvh mode in pure pv paths")
---
 drivers/xen/balloon.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index ab60925..f77e499 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -664,9 +664,11 @@ int alloc_xenballooned_pages(int nr_pages, struct page **pages)
 			 */
 			BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
 
-			ret = xen_alloc_p2m_entry(page_to_pfn(page));
-			if (ret < 0)
-				goto out_undo;
+			if (!xen_feature(XENFEAT_auto_translated_physmap)) {
+				ret = xen_alloc_p2m_entry(page_to_pfn(page));
+				if (ret < 0)
+					goto out_undo;
+			}
 #endif
 		} else {
 			ret = add_ballooned_pages(nr_pages - pgno);
-- 
1.8.3.1