From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from co1ehsobe004.messaging.microsoft.com ([216.32.180.187]:49572 "EHLO co1outboundpool.messaging.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753361Ab3HWXHy (ORCPT ); Fri, 23 Aug 2013 19:07:54 -0400 Message-ID: <5217EB44.3020302@amd.com> Date: Fri, 23 Aug 2013 18:07:48 -0500 From: Aravind Gopalakrishnan MIME-Version: 1.0 To: Borislav Petkov CC: , , , , , , , , Subject: Re: [PATCH 1/1] AMD64_EDAC: Fix incorrect wrap arounds due to left shift beyond 32 bits. References: <1376958472-2150-1-git-send-email-Aravind.Gopalakrishnan@amd.com> <1376958472-2150-2-git-send-email-Aravind.Gopalakrishnan@amd.com> <20130823213725.GC15521@pd.tnic> In-Reply-To: <20130823213725.GC15521@pd.tnic> Content-Type: text/plain; charset="UTF-8"; format=flowed Sender: linux-pci-owner@vger.kernel.org List-ID: On 8/23/2013 4:37 PM, Borislav Petkov wrote: > On Mon, Aug 19, 2013 at 07:27:52PM -0500, Aravind Gopalakrishnan wrote: >> Link to the bug report: >> http://marc.info/?l=linux-edac&m=137692201732220&w=2 >> >> dct_base and dct_limit obtain 32 bit register values when they read their >> respective pci config space registers. A left shift beyond 32 bits will >> cause them to wrap around. Similar case for chan_addr as can be seen from >> the bug report. In the patch, we rectify this by casting chan_addr to u64 >> and by comparing dct_base and dct_limit against (sys_addr >> 27) >> >> Tested on F15h, M30h with ECC turned on and works fine. >> >> Signed-off-by: Aravind Gopalakrishnan >> >> diff --git a/drivers/edac/amd64_edac.c b/drivers/edac/amd64_edac.c >> index b86228c..eb4793e 100644 >> --- a/drivers/edac/amd64_edac.c >> +++ b/drivers/edac/amd64_edac.c >> @@ -1558,11 +1558,12 @@ static int f15_m30h_match_to_this_node(struct amd64_pvt *pvt, unsigned range, >> } >> >> /* Verify sys_addr is within DCT Range. */ >> - dct_base = (dct_sel_baseaddr(pvt) << 27); >> - dct_limit = (((dct_cont_limit_reg >> 11) & 0x1FFF) << 27) | 0x7FFFFFF; >> + dct_base = dct_sel_baseaddr(pvt); > This can't be correct. > > So the original patch takes the shifted dct_base while your change > doesn't anymore... > >> + dct_limit = (dct_cont_limit_reg >> 11) & 0x1FFF; >> >> if (!(dct_cont_base_reg & BIT(0)) && >> - !(dct_base <= sys_addr && dct_limit >= sys_addr)) >> + !(dct_base <= (sys_addr >> 27) && >> + dct_limit >= (sys_addr >> 27))) > ... and while this comparison shifts sys_addr to use the proper bits, > the code does this assignment later: > > chan_offset = dct_base; > > Now, chan_offset has the << 27 version of dct_base which makes the following > calculation wrong: > > chan_addr = sys_addr - chan_offset; Oops. my apologies. > because sys_addr is the full 64-bit, unshifted value. > > The right thing to do would be to do: > > chan_offset = dct_base << 27; > > Or am I missing something? > No, you are right. I am re-sending the patch. Thanks, -Aravind.