From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: [PATCH] MTRR: clear DramModEn bit of sys_cfg MSR Date: Tue, 05 Apr 2011 19:12:39 +0100 Message-ID: References: <4D9B50D2.8040900@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4D9B50D2.8040900@amd.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Wei Huang Cc: "'xen-devel@lists.xensource.com'" List-Id: xen-devel@lists.xenproject.org Looks good, thanks! -- Keir On 05/04/2011 18:26, "Wei Huang" wrote: > Sorry for the indention issue... I agree that it is better to move > check-and_fixup code to init_amd() function. See the new patch. > > My understanding is that RdMem and WrMem are never going to become 1: > BIOS are supposed to set sys_cfg[DramModEn] bit to 0 before OS takes > over. As a result, RdMem and WrMem are read as 0 in fixed MTRRs. Unless > Xen turn these bits to 1 (which I don't see from the code), > k8_enable_fixed_iorrs() is useless. My 2nd patch removes > k8_enable_fixed_iorrs(). If you have concern, we don't have to apply > this patch. But I don't think we shouldn't move it to amd.c. > k8_enable_fixed_iorrs() is unrelated in that file. > > Thanks, > -Wei > > On 04/05/2011 06:51 AM, Keir Fraser wrote: >> On 04/04/2011 23:23, "Wei Huang" wrote: >> >>> Some buggy BIOS might set sys_cfg DramModEn bit to 1, which can cause >>> unexpected behavior on AMD platforms. This patch clears DramModEn bit. >>> The patch was derived from upstream kernel patch (see >>> https://patchwork.kernel.org/patch/11425/). >> This patch also removes k8_enable_fixed_iorrs(), and it's not clear why. >> That would at least belong in a separate patch, but I would think we don't >> want to delete that code anyway. >> >> The indentation is wrong (spaces in a file that is hard-tab-indented). And >> the printk is probably unnecessary -- at most you should print it once >> rather than potentially for every core brought up. >> >> But further, I don't see why you need to hang off {get,set}_fixed_ranges at >> all. Why not do this check-and-fixup in cpu/amd.c:init_amd()? It's a handy >> early-cpu-bringup amd-specific function which is rather designed ofr this >> kind of purpose. The k8_enable_fixed_iorrs() work could better be done in >> the same place, too (perhaps move it in a separate patch?). >> >> -- Keir >> >>> Signed-off-by: Wei Huang >>> >>> >>> >>> >>> _______________________________________________ >>> Xen-devel mailing list >>> Xen-devel@lists.xensource.com >>> http://lists.xensource.com/xen-devel >> >> >