From patchwork Wed May 11 10:16:45 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Vrabel X-Patchwork-Id: 9067261 Return-Path: X-Original-To: patchwork-xen-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 8F0FBBF29F for ; Wed, 11 May 2016 10:19:18 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 69BD8201C7 for ; Wed, 11 May 2016 10:19:17 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9725C20145 for ; Wed, 11 May 2016 10:19:15 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.84_2) (envelope-from ) id 1b0RCM-0007kF-E0; Wed, 11 May 2016 10:16:58 +0000 Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xenproject.org with esmtp (Exim 4.84_2) (envelope-from ) id 1b0RCK-0007k9-Hb for xen-devel@lists.xen.org; Wed, 11 May 2016 10:16:56 +0000 Received: from [85.158.137.68] by server-5.bemta-3.messagelabs.com id 41/E1-03651-79603375; Wed, 11 May 2016 10:16:55 +0000 X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFlrOIsWRWlGSWpSXmKPExsXitHRDpO50NuN wg+nnJCyWfFzM4sDocXT3b6YAxijWzLyk/IoE1ox7S6cxFTxRqbjQPoelgfGYXBcjJ4eEgL/E 93vzGLsYOTiEBewkHn7IAgmLCLhIvJ+5l6mLkYtDSKCTVWL++59MIAlmgQKJphvLwGw2AR2Jx 0tmsIPYvAKaEs0NJ1lAbBYBVYnv62awgdiiAsESdy48Z4OoEZQ4OfMJWA2ngIbE0TaIvcxAve t36UOMl5fY/nYOM4gtJKAi8XHtKlaIM7klbp+eyjyBkX8WkkmzELpnIelewMi8ilGjOLWoLLV I19BcL6koMz2jJDcxM0fX0MBYLze1uDgxPTUnMalYLzk/dxMjMAAZgGAH48vTnocYJTmYlER5 +18ahQvxJeWnVGYkFmfEF5XmpBYfYpTh4FCS4C1mNQ4XEixKTU+tSMvMAcYCTFqCg0dJhPcEC 1Cat7ggMbc4Mx0idYpRUUqcNxekTwAkkVGaB9cGi79LjLJSwryMQIcI8RSkFuVmlqDKv2IU52 BUEuZNBJnCk5lXAjf9FdBiJqDF1deNQBaXJCKkpBoY16Y1bGwwj9mrfWdVQOXOqtLPu4r/PZs zI4tXnIl5t9iMhpsaBzJ1OO9YsbdrvfAQrim4dV3Xakrxz10JeRFzDxt4W7O9N91zlG+zi8D+ rjuFnEzB8/mdQ4Xf9Gleb+Ur/3qihydSVvtoSBsvY9XxF9PtFLu1XjuFnhFf+0cuyNmmb+OiO GclluKMREMt5qLiRAAM9CqUugIAAA== X-Env-Sender: prvs=932dcd7bd=david.vrabel@citrix.com X-Msg-Ref: server-2.tower-31.messagelabs.com!1462961812!39541243!1 X-Originating-IP: [66.165.176.89] X-SpamReason: No, hits=0.0 required=7.0 tests=sa_preprocessor: VHJ1c3RlZCBJUDogNjYuMTY1LjE3Ni44OSA9PiAyMDMwMDc=\n, received_headers: No Received headers X-StarScan-Received: X-StarScan-Version: 8.34; banners=-,-,- X-VirusChecked: Checked Received: (qmail 60165 invoked from network); 11 May 2016 10:16:54 -0000 Received: from smtp.citrix.com (HELO SMTP.CITRIX.COM) (66.165.176.89) by server-2.tower-31.messagelabs.com with RC4-SHA encrypted SMTP; 11 May 2016 10:16:54 -0000 X-IronPort-AV: E=Sophos;i="5.24,608,1454976000"; d="scan'208";a="353112893" To: Juergen Gross , Jan Beulich References: <572FC2F9.3060200@riseup.net> <57307DD402000078000E9622@prv-mh.provo.novell.com> <5730A447.3010505@riseup.net> <5730CE7E02000078000E9A8A@prv-mh.provo.novell.com> <5730BD86.6080407@riseup.net> <5730C5A4.9040008@oracle.com> <5730C73E.8030007@riseup.net> <5730D994.6050100@oracle.com> <5731A87502000078000E9D8C@prv-mh.provo.novell.com> <5731E4A5.30906@oracle.com> <5732050602000078000EA230@prv-mh.provo.novell.com> <5731FBEA.4010202@suse.com> <57321BFA02000078000EA3C2@suse.com> <573201AE.1010306@suse.com> <57320DD3.3030805@oracle.com> <5732C7D0.4050907@suse.com> <5732EEBF02000078000EA613@suse.com> <5732D893.7000503@suse.com> From: David Vrabel Message-ID: <5733068D.5050604@citrix.com> Date: Wed, 11 May 2016 11:16:45 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Icedove/38.5.0 MIME-Version: 1.0 In-Reply-To: <5732D893.7000503@suse.com> X-DLP: MIA2 Cc: Kevin Moraga , Boris Ostrovsky , xen-devel@lists.xen.org Subject: Re: [Xen-devel] crash on boot with 4.6.1 on fedora 24 X-BeenThere: xen-devel@lists.xen.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xen.org Sender: "Xen-devel" X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On 11/05/16 08:00, Juergen Gross wrote: > On 11/05/16 08:35, Jan Beulich wrote: >>>>> On 11.05.16 at 07:49, wrote: >>> On 10/05/16 18:35, Boris Ostrovsky wrote: >>>> On 05/10/2016 11:43 AM, Juergen Gross wrote: >>>>> On 10/05/16 17:35, Jan Beulich wrote: >>>>>>>>> On 10.05.16 at 17:19, wrote: >>>>>>> On 10/05/16 15:57, Jan Beulich wrote: >>>>>>>>>>> On 10.05.16 at 15:39, wrote: >>>>>>>>> I didn't finish unwrapping the stack yesterday. Here it is: >>>>>>>>> >>>>>>>>> setup_arch -> dmi_scan_machine -> dmi_walk_early -> early_ioremap >>>>>>>> Ah, that makes sense. Yet why would early_ioremap() involve an >>>>>>>> M2P lookup? As said, MMIO addresses shouldn't be subject to such >>>>>>>> lookups. >>>>>>> early_ioremap()-> >>>>>>> __early_ioremap()-> >>>>>>> __early_set_fixmap()-> >>>>>>> set_pte()-> >>>>>>> xen_set_pte_init()-> >>>>>>> mask_rw_pte()-> >>>>>>> pte_pfn()-> >>>>>>> pte_val()-> >>>>>>> xen_pte_val()-> >>>>>>> pte_mfn_to_pfn() >>>>>> Well, I understand (also from Boris' first reply) that's how it is, >>>>>> but not why it is so. I.e. the call flow above doesn't answer my >>>>>> question. >>>>> On x86 early_ioremap() and early_memremap() share a common sub-function >>>>> __early_ioremap(). This together with pvops requires a common set_pte() >>>>> implementation leading to the mfn validation in the end. >>>> >>>> Do we make any assumptions about where DMI data lives? >>> >>> I don't think so. >>> >>> So the basic problem is the page fault due to the sparse m2p map before >>> the #PF handler is registered. >>> >>> What do you think about registering a minimal #PF handler in >>> xen_arch_setup() being capable to handle this problem? This should be >>> doable without major problems. I can do a patch. >> >> To me that would feel like working around the issue instead of >> admitting that the removal of _PAGE_IOMAP was a mistake. > > Hmm, I don't think so. > > Having a Xen specific pte flag seems to be much more intrusive than > having an early boot page fault handler consisting of just one line > being capable to mimic the default handler in just one aspect (see > attached patch - only compile tested). > > Adding David as he removed _PAGE_IOMAP in kernel 3.18. Why don't we get the RW bits correct when making the pteval when we already have the pfn, instead trying to fix it up afterwards. Something like this: @@ -1577,7 +1593,7 @@ static pte_t __init mask_rw_pte(pte_t *ptep, pte_t pte) * page tables for mapping the p2m list, too, and page tables MUST be * mapped read-only. */ - pfn = pte_pfn(pte); + pfn = pte_mfn(pte); if (pfn >= xen_start_info->first_p2m_pfn && pfn < xen_start_info->first_p2m_pfn + xen_start_info->nr_p2m_frames) pte = __pte_ma(pte_val_ma(pte) & ~_PAGE_RW); @@ -1602,11 +1618,10 @@ static pte_t __init mask_rw_pte(pte_t *ptep, pte_t pte) */ static void __init xen_set_pte_init(pte_t *ptep, pte_t pte) { +#ifdef CONFIG_X86_32 if (pte_mfn(pte) != INVALID_P2M_ENTRY) pte = mask_rw_pte(ptep, pte); - else - pte = __pte_ma(0); - +#endif native_set_pte(ptep, pte); } @@ -2407,6 +2422,7 @@ static void __init xen_post_allocator_init(void) pv_mmu_ops.alloc_pud = xen_alloc_pud; pv_mmu_ops.release_pud = xen_release_pud; #endif + pv_mmu_ops.make_pte = xen_make_pte; #ifdef CONFIG_X86_64 pv_mmu_ops.write_cr3 = &xen_write_cr3; @@ -2455,7 +2471,7 @@ static const struct pv_mmu_ops xen_mmu_ops __initconst = { .pte_val = PV_CALLEE_SAVE(xen_pte_val), .pgd_val = PV_CALLEE_SAVE(xen_pgd_val), - .make_pte = PV_CALLEE_SAVE(xen_make_pte), + .make_pte = PV_CALLEE_SAVE(xen_make_pte_init), .make_pgd = PV_CALLEE_SAVE(xen_make_pgd), #ifdef CONFIG_X86_PAE diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c index 478a2de..d187368 100644 --- a/arch/x86/xen/mmu.c +++ b/arch/x86/xen/mmu.c @@ -430,6 +430,22 @@ __visible pte_t xen_make_pte(pteval_t pte) } PV_CALLEE_SAVE_REGS_THUNK(xen_make_pte); +__visible __init pte_t xen_make_pte_init(pteval_t pte) +{ + unsigned long pfn = pte_mfn(pte); + +#ifdef CONFIG_X86_64 + pte = mask_rw_pte(pte); +#endif + pte = pte_pfn_to_mfn(pte); + + if (pte_mfn(pte) == INVALID_P2M_ENTRY) + pte = __pte_ma(0); + + return native_make_pte(pte); +} +PV_CALLEE_SAVE_REGS_THUNK(xen_make_pte); + __visible pgd_t xen_make_pgd(pgdval_t pgd) { pgd = pte_pfn_to_mfn(pgd); @@ -1562,7 +1578,7 @@ static pte_t __init mask_rw_pte(pte_t *ptep, pte_t pte) return pte; } #else /* CONFIG_X86_64 */ -static pte_t __init mask_rw_pte(pte_t *ptep, pte_t pte) +static pte_t __init mask_rw_pte(pte_t pte) { unsigned long pfn;