From 60901df3aed230d4565dca003f11b6a95fbf30d9 Mon Sep 17 00:00:00 2001 From: Ross Lagerwall Date: Thu, 17 Mar 2016 16:51:59 +0000 Subject: [PATCH] xen: Fix page <-> pfn conversion on 32 bit systems Commit 1084b1988d22dc165c9dbbc2b0e057f9248ac4db (xen: Add Xen specific page definition) caused a regression in 4.4. The xen functions to convert between pages and pfns fail due to an overflow on systems where a physical address may not fit in an unsigned long (e.g. x86 32 bit PAE systems). Rework the conversion to avoid overflow. This should also result in simpler object code. This bug manifested itself as disk corruption with Linux 4.4 when using blkfront in a Xen HVM x86 32 bit guest with more than 4 GiB of memory. Signed-off-by: Ross Lagerwall Cc: # 4.4+ Signed-off-by: David Vrabel --- include/xen/page.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/xen/page.h b/include/xen/page.h index 96294ac93755..9dc46cb8a0fd 100644 --- a/include/xen/page.h +++ b/include/xen/page.h @@ -15,9 +15,9 @@ */ #define xen_pfn_to_page(xen_pfn) \ - ((pfn_to_page(((unsigned long)(xen_pfn) << XEN_PAGE_SHIFT) >> PAGE_SHIFT))) + (pfn_to_page((unsigned long)(xen_pfn) >> (PAGE_SHIFT - XEN_PAGE_SHIFT))) #define page_to_xen_pfn(page) \ - (((page_to_pfn(page)) << PAGE_SHIFT) >> XEN_PAGE_SHIFT) + ((page_to_pfn(page)) << (PAGE_SHIFT - XEN_PAGE_SHIFT)) #define XEN_PFN_PER_PAGE (PAGE_SIZE / XEN_PAGE_SIZE) -- 2.30.2