From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D3A4EC6778D for ; Wed, 12 Sep 2018 15:13:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 805BC20880 for ; Wed, 12 Sep 2018 15:13:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 805BC20880 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727984AbeILUSh (ORCPT ); Wed, 12 Sep 2018 16:18:37 -0400 Received: from mga12.intel.com ([192.55.52.136]:33077 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726640AbeILUSh (ORCPT ); Wed, 12 Sep 2018 16:18:37 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 12 Sep 2018 08:13:40 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.53,365,1531810800"; d="scan'208";a="88146928" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.20]) by fmsmga004.fm.intel.com with ESMTP; 12 Sep 2018 08:09:39 -0700 Date: Wed, 12 Sep 2018 08:09:39 -0700 From: Sean Christopherson To: Will Deacon Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, cpandya@codeaurora.org, toshi.kani@hpe.com, tglx@linutronix.de, mhocko@suse.com, akpm@linux-foundation.org Subject: Re: [PATCH 4/5] lib/ioremap: Ensure phys_addr actually corresponds to a physical address Message-ID: <20180912150939.GA30274@linux.intel.com> References: <1536747974-25875-1-git-send-email-will.deacon@arm.com> <1536747974-25875-5-git-send-email-will.deacon@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1536747974-25875-5-git-send-email-will.deacon@arm.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 12, 2018 at 11:26:13AM +0100, Will Deacon wrote: > The current ioremap() code uses a phys_addr variable at each level of > page table, which is confusingly offset by subtracting the base virtual > address being mapped so that adding the current virtual address back on > when iterating through the page table entries gives back the corresponding > physical address. > > This is fairly confusing and results in all users of phys_addr having to > add the current virtual address back on. Instead, this patch just updates > phys_addr when iterating over the page table entries, ensuring that it's > always up-to-date and doesn't require explicit offsetting. > > Cc: Chintan Pandya > Cc: Toshi Kani > Cc: Thomas Gleixner > Cc: Michal Hocko > Cc: Andrew Morton > Signed-off-by: Will Deacon > --- > lib/ioremap.c | 28 ++++++++++++---------------- > 1 file changed, 12 insertions(+), 16 deletions(-) > > diff --git a/lib/ioremap.c b/lib/ioremap.c > index 6c72764af19c..fc834a59c90c 100644 > --- a/lib/ioremap.c > +++ b/lib/ioremap.c > @@ -101,19 +101,18 @@ static inline int ioremap_pmd_range(pud_t *pud, unsigned long addr, > pmd_t *pmd; > unsigned long next; > > - phys_addr -= addr; > pmd = pmd_alloc(&init_mm, pud, addr); > if (!pmd) > return -ENOMEM; > do { > next = pmd_addr_end(addr, end); > > - if (ioremap_try_huge_pmd(pmd, addr, next, phys_addr + addr, prot)) > + if (ioremap_try_huge_pmd(pmd, addr, next, phys_addr, prot)) > continue; > > - if (ioremap_pte_range(pmd, addr, next, phys_addr + addr, prot)) > + if (ioremap_pte_range(pmd, addr, next, phys_addr, prot)) > return -ENOMEM; > - } while (pmd++, addr = next, addr != end); > + } while (pmd++, addr = next, phys_addr += PMD_SIZE, addr != end); I think bumping phys_addr by PXX_SIZE is wrong if phys_addr and addr start unaligned with respect to PXX_SIZE. The addresses must be PAGE_ALIGNED, which lets ioremap_pte_range() do a simple calculation, but that doesn't hold true for the upper levels, i.e. phys_addr needs to be adjusted using an algorithm similar to pxx_addr_end(). Using a 2mb page as an example (lower 32 bits only): pxx_size = 0x00020000 pxx_mask = 0xfffe0000 addr = 0x1000 end = 0x00040000 phys_addr = 0x1000 Loop 1: addr = 0x1000 phys = 0x1000 Loop 2: addr = 0x20000 phys = 0x21000 > return 0; > } > > @@ -142,19 +141,18 @@ static inline int ioremap_pud_range(p4d_t *p4d, unsigned long addr, > pud_t *pud; > unsigned long next; > > - phys_addr -= addr; > pud = pud_alloc(&init_mm, p4d, addr); > if (!pud) > return -ENOMEM; > do { > next = pud_addr_end(addr, end); > > - if (ioremap_try_huge_pud(pud, addr, next, phys_addr + addr, prot)) > + if (ioremap_try_huge_pud(pud, addr, next, phys_addr, prot)) > continue; > > - if (ioremap_pmd_range(pud, addr, next, phys_addr + addr, prot)) > + if (ioremap_pmd_range(pud, addr, next, phys_addr, prot)) > return -ENOMEM; > - } while (pud++, addr = next, addr != end); > + } while (pud++, addr = next, phys_addr += PUD_SIZE, addr != end); > return 0; > } > > @@ -164,7 +162,6 @@ static inline int ioremap_p4d_range(pgd_t *pgd, unsigned long addr, > p4d_t *p4d; > unsigned long next; > > - phys_addr -= addr; > p4d = p4d_alloc(&init_mm, pgd, addr); > if (!p4d) > return -ENOMEM; > @@ -173,14 +170,14 @@ static inline int ioremap_p4d_range(pgd_t *pgd, unsigned long addr, > > if (ioremap_p4d_enabled() && > ((next - addr) == P4D_SIZE) && > - IS_ALIGNED(phys_addr + addr, P4D_SIZE)) { > - if (p4d_set_huge(p4d, phys_addr + addr, prot)) > + IS_ALIGNED(phys_addr, P4D_SIZE)) { > + if (p4d_set_huge(p4d, phys_addr, prot)) > continue; > } > > - if (ioremap_pud_range(p4d, addr, next, phys_addr + addr, prot)) > + if (ioremap_pud_range(p4d, addr, next, phys_addr, prot)) > return -ENOMEM; > - } while (p4d++, addr = next, addr != end); > + } while (p4d++, addr = next, phys_addr += P4D_SIZE, addr != end); > return 0; > } > > @@ -196,14 +193,13 @@ int ioremap_page_range(unsigned long addr, > BUG_ON(addr >= end); > > start = addr; > - phys_addr -= addr; > pgd = pgd_offset_k(addr); > do { > next = pgd_addr_end(addr, end); > - err = ioremap_p4d_range(pgd, addr, next, phys_addr+addr, prot); > + err = ioremap_p4d_range(pgd, addr, next, phys_addr, prot); > if (err) > break; > - } while (pgd++, addr = next, addr != end); > + } while (pgd++, addr = next, phys_addr += PGDIR_SIZE, addr != end); > > flush_cache_vmap(start, end); > > -- > 2.1.4 >