From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752601AbeEKHda (ORCPT ); Fri, 11 May 2018 03:33:30 -0400 Received: from mx2.suse.de ([195.135.220.15]:54314 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752174AbeEKHd3 (ORCPT ); Fri, 11 May 2018 03:33:29 -0400 Subject: Re: [Xen-devel] [PATCH v2 1/3] xen/pvh: enable and set default MTRR type To: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , Andrew Cooper Cc: xen-devel@lists.xenproject.org, Boris Ostrovsky , linux-kernel@vger.kernel.org References: <20180509102129.14832-1-roger.pau@citrix.com> <20180509102129.14832-2-roger.pau@citrix.com> <20180509113016.tavac64ba5fu3tob@MacBook-Pro-de-Roger.local> <20180509151139.nytwuepervqjkcat@MacBook-Pro-de-Roger.local> From: Juergen Gross Message-ID: Date: Fri, 11 May 2018 09:33:27 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180509151139.nytwuepervqjkcat@MacBook-Pro-de-Roger.local> Content-Type: text/plain; charset=utf-8 Content-Language: de-DE Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/05/18 17:11, Roger Pau Monné wrote: > On Wed, May 09, 2018 at 12:30:16PM +0100, Roger Pau Monné wrote: >> On Wed, May 09, 2018 at 11:56:40AM +0100, Andrew Cooper wrote: >>> On 09/05/18 11:21, Roger Pau Monne wrote: >>> I'm not sure that setting the default MTRR type is going to be a >>> clever idea in hindsight when we come to doing PCI Passthrough support. >> >> Setting the default type to WB is also set by hvmloader, it's just >> that hvmloader also sets some of the fixed and variable ranges to UC >> in order to cover the iomem areas. >> >> The expectations when doing pci-passthrough is that the guest will >> always use paging and PAT in order to set the appropriate cache >> attributes, or else the guest itself will have to program the UC MTRR >> ranges, I admit that's not very nice however. >> >> What about enabling the default MTRR type and setting it to WB in the >> toolstack for PVH? IMO doing it Xen itself would be wrong. > > I have the following patch to set the default MTRR type, but I think > if we go down this road then we will also have to set UC MTRRs for > MMIO areas, which again seems fine to me. I like this route much better. Juergen > > ---8<--- > diff --git a/tools/libxc/xc_dom_x86.c b/tools/libxc/xc_dom_x86.c > index e33a28847d..3cb1a1720f 100644 > --- a/tools/libxc/xc_dom_x86.c > +++ b/tools/libxc/xc_dom_x86.c > @@ -938,6 +938,8 @@ static int vcpu_hvm(struct xc_dom_image *dom) > HVM_SAVE_TYPE(HEADER) header; > struct hvm_save_descriptor cpu_d; > HVM_SAVE_TYPE(CPU) cpu; > + struct hvm_save_descriptor mtrr_d; > + HVM_SAVE_TYPE(MTRR) mtrr; > struct hvm_save_descriptor end_d; > HVM_SAVE_TYPE(END) end; > } bsp_ctx; > @@ -1014,6 +1016,15 @@ static int vcpu_hvm(struct xc_dom_image *dom) > if ( dom->start_info_seg.pfn ) > bsp_ctx.cpu.rbx = dom->start_info_seg.pfn << PAGE_SHIFT; > > + /* Set the MTRR. */ > + bsp_ctx.mtrr_d.typecode = HVM_SAVE_CODE(MTRR); > + bsp_ctx.mtrr_d.instance = 0; > + bsp_ctx.mtrr_d.length = HVM_SAVE_LENGTH(MTRR); > + /* XXX: maybe this should be a firmware option instead? */ > + if ( !dom->device_model ) > + /* Enable MTRR (bit 11) and set the default type to WB (6). */ > + bsp_ctx.mtrr.msr_mtrr_def_type = (1u << 11) | 6; > + > /* Set the end descriptor. */ > bsp_ctx.end_d.typecode = HVM_SAVE_CODE(END); > bsp_ctx.end_d.instance = 0; > >