Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Christian Borntraeger , Juergen Gross , David Vrabel Subject: [PATCH 3.19 175/175] x86/xen/p2m: Replace ACCESS_ONCE with READ_ONCE Date: Tue, 3 Mar 2015 22:15:53 -0800 Message-Id: <20150304061054.891018690@linuxfoundation.org> In-Reply-To: <20150304061026.134125919@linuxfoundation.org> References: <20150304061026.134125919@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Christian Borntraeger commit 1760f1eb7ec485197bd3a8a9c13e4160bb740275 upstream. ACCESS_ONCE does not work reliably on non-scalar types. For example gcc 4.6 and 4.7 might remove the volatile tag for such accesses during the SRA (scalar replacement of aggregates) step (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145) Change the p2m code to replace ACCESS_ONCE with READ_ONCE. Signed-off-by: Christian Borntraeger Reviewed-by: Juergen Gross Acked-by: David Vrabel Signed-off-by: Greg Kroah-Hartman --- arch/x86/xen/p2m.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/arch/x86/xen/p2m.c +++ b/arch/x86/xen/p2m.c @@ -554,7 +554,7 @@ static bool alloc_p2m(unsigned long pfn) mid_mfn = NULL; } - p2m_pfn = pte_pfn(ACCESS_ONCE(*ptep)); + p2m_pfn = pte_pfn(READ_ONCE(*ptep)); if (p2m_pfn == PFN_DOWN(__pa(p2m_identity)) || p2m_pfn == PFN_DOWN(__pa(p2m_missing))) { /* p2m leaf page is missing */