linux-kernel - [PATCH 3.16 080/125] x86/xen: use vmap() to map grant table pages in PVH guests

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Date:	Wed,  3 Sep 2014 15:07:17 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, David Vrabel <david.vrabel@...rix.com>,
	Mukesh Rathor <mukesh.rathor@...cle.com>
Subject: [PATCH 3.16 080/125] x86/xen: use vmap() to map grant table pages in PVH guests

3.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Vrabel <david.vrabel@...rix.com>

commit 7d951f3ccb0308c95bf76d5eef9886dea35a7013 upstream.

Commit b7dd0e350e0b (x86/xen: safely map and unmap grant frames when
in atomic context) causes PVH guests to crash in
arch_gnttab_map_shared() when they attempted to map the pages for the
grant table.

This use of a PV-specific function during the PVH grant table setup is
non-obvious and not needed.  The standard vmap() function does the
right thing.

Signed-off-by: David Vrabel <david.vrabel@...rix.com>
Reported-by: Mukesh Rathor <mukesh.rathor@...cle.com>
Tested-by: Mukesh Rathor <mukesh.rathor@...cle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/xen/grant-table.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

--- a/arch/x86/xen/grant-table.c
+++ b/arch/x86/xen/grant-table.c
@@ -168,6 +168,7 @@ static int __init xlated_setup_gnttab_pa
 {
 	struct page **pages;
 	xen_pfn_t *pfns;
+	void *vaddr;
 	int rc;
 	unsigned int i;
 	unsigned long nr_grant_frames = gnttab_max_grant_frames();
@@ -193,21 +194,20 @@ static int __init xlated_setup_gnttab_pa
 	for (i = 0; i < nr_grant_frames; i++)
 		pfns[i] = page_to_pfn(pages[i]);
 
-	rc = arch_gnttab_map_shared(pfns, nr_grant_frames, nr_grant_frames,
-				    &xen_auto_xlat_grant_frames.vaddr);
-
-	if (rc) {
+	vaddr = vmap(pages, nr_grant_frames, 0, PAGE_KERNEL);
+	if (!vaddr) {
 		pr_warn("%s Couldn't map %ld pfns rc:%d\n", __func__,
 			nr_grant_frames, rc);
 		free_xenballooned_pages(nr_grant_frames, pages);
 		kfree(pages);
 		kfree(pfns);
-		return rc;
+		return -ENOMEM;
 	}
 	kfree(pages);
 
 	xen_auto_xlat_grant_frames.pfn = pfns;
 	xen_auto_xlat_grant_frames.count = nr_grant_frames;
+	xen_auto_xlat_grant_frames.vaddr = vaddr;
 
 	return 0;
 }


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