Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754453AbbGXQxa (ORCPT ); Fri, 24 Jul 2015 12:53:30 -0400 Received: from foss.arm.com ([217.140.101.70]:46214 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752391AbbGXQx2 (ORCPT ); Fri, 24 Jul 2015 12:53:28 -0400 Date: Fri, 24 Jul 2015 17:53:25 +0100 From: Will Deacon To: Yong Wu Cc: Joerg Roedel , Thierry Reding , Mark Rutland , Matthias Brugger , Robin Murphy , Daniel Kurtz , Tomasz Figa , Lucas Stach , Rob Herring , Catalin Marinas , "linux-mediatek@lists.infradead.org" , Sasha Hauer , "srv_heupstream@mediatek.com" , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "iommu@lists.linux-foundation.org" , "pebolle@tiscali.nl" , "arnd@arndb.de" , "mitchelh@codeaurora.org" , "cloud.chou@mediatek.com" , "frederic.chen@mediatek.com" Subject: Re: [PATCH v3 3/6] iommu: add ARM short descriptor page table allocator. Message-ID: <20150724165325.GC21177@arm.com> References: <1437037475-9065-1-git-send-email-yong.wu@mediatek.com> <1437037475-9065-4-git-send-email-yong.wu@mediatek.com> <20150721171101.GN31095@arm.com> <1437715466.23932.68.camel@mhfsdcap03> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1437715466.23932.68.camel@mhfsdcap03> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4897 Lines: 111 On Fri, Jul 24, 2015 at 06:24:26AM +0100, Yong Wu wrote: > On Tue, 2015-07-21 at 18:11 +0100, Will Deacon wrote: > > On Thu, Jul 16, 2015 at 10:04:32AM +0100, Yong Wu wrote: > > > +/* level 2 pagetable */ > > > +#define ARM_SHORT_PTE_TYPE_LARGE BIT(0) > > > +#define ARM_SHORT_PTE_SMALL_XN BIT(0) > > > +#define ARM_SHORT_PTE_TYPE_SMALL BIT(1) > > > +#define ARM_SHORT_PTE_B BIT(2) > > > +#define ARM_SHORT_PTE_C BIT(3) > > > +#define ARM_SHORT_PTE_SMALL_TEX0 BIT(6) > > > +#define ARM_SHORT_PTE_IMPLE BIT(9) > > > > This is AP[2] for small pages. > > Sorry, In our pagetable bit9 in PGD and PTE is PA[32] that is for the > dram size over 4G. I didn't care it is different in PTE of the standard > spec. > And I don't use the AP[2] currently, so I only delete this line in next > time. Is this related to the "special bit". What would be good is a comment next to the #define for the quirk describing *exactly* that differs in your implementation. Without that, it's very difficult to know what is intentional and what is actually broken. > > > +static arm_short_iopte > > > +__arm_short_pte_prot(struct arm_short_io_pgtable *data, int prot, bool large) > > > +{ > > > + arm_short_iopte pteprot; > > > + > > > + pteprot = ARM_SHORT_PTE_S | ARM_SHORT_PTE_nG; > > > + pteprot |= large ? ARM_SHORT_PTE_TYPE_LARGE : > > > + ARM_SHORT_PTE_TYPE_SMALL; > > > + if (prot & IOMMU_CACHE) > > > + pteprot |= ARM_SHORT_PTE_B | ARM_SHORT_PTE_C; > > > + if (prot & IOMMU_WRITE) > > > + pteprot |= large ? ARM_SHORT_PTE_LARGE_TEX0 : > > > + ARM_SHORT_PTE_SMALL_TEX0; > > > > This doesn't make any sense. TEX[2:0] is all about memory attributes, not > > permissions, so you're making the mapping write-back, write-allocate but > > that's not what the IOMMU_* values are about. > > I will delete it. Well, can you not control mapping permissions with the AP bits? The idea of the IOMMU flags are: IOMMU_CACHE : Install a normal, cacheable mapping (you've got this right) IOMMU_READ : Allow read access for the device IOMMU_WRITE : Allow write access for the device IOMMU_NOEXEC : Disallow execute access for the device so the caller to iommu_map passes in a bitmap of these, which you need to encode in the page-table entry. > > > +static int > > > +_arm_short_map(struct arm_short_io_pgtable *data, > > > + unsigned int iova, phys_addr_t paddr, > > > + arm_short_iopte pgdprot, arm_short_iopte pteprot, > > > + bool large) > > > +{ > > > + const struct iommu_gather_ops *tlb = data->iop.cfg.tlb; > > > + arm_short_iopte *pgd = data->pgd, *pte; > > > + void *cookie = data->iop.cookie, *pte_va; > > > + unsigned int ptenr = large ? 16 : 1; > > > + int i, quirk = data->iop.cfg.quirks; > > > + bool ptenew = false; > > > + > > > + pgd += ARM_SHORT_PGD_IDX(iova); > > > + > > > + if (!pteprot) { /* section or supersection */ > > > + if (quirk & IO_PGTABLE_QUIRK_SHORT_MTK) > > > + pgdprot &= ~ARM_SHORT_PGD_SECTION_XN; > > > + pte = pgd; > > > + pteprot = pgdprot; > > > + } else { /* page or largepage */ > > > + if (quirk & IO_PGTABLE_QUIRK_SHORT_MTK) { > > > + if (large) { /* special Bit */ > > > > This definitely needs a better comment! What exactly are you doing here > > and what is that quirk all about? > > I use this quirk is for MTK Special Bit as we don't have the XN bit in > pagetable. I'm still not really clear about what this is. > > > + if (!(*pgd)) { > > > + pte_va = kmem_cache_zalloc(data->ptekmem, GFP_ATOMIC); > > > + if (unlikely(!pte_va)) > > > + return -ENOMEM; > > > + ptenew = true; > > > + *pgd = virt_to_phys(pte_va) | pgdprot; > > > + kmemleak_ignore(pte_va); > > > + tlb->flush_pgtable(pgd, sizeof(*pgd), cookie); > > > > I think you need to flush this before it becomes visible to the walker. > > I have flushed pgtable here, Do you meaning flush tlb here? No. afaict, you allocate the pte table using kmem_cache_zalloc but you never flush it. However, you update the pgd to point at this table, so the walker can potentially see garbage instead of the zeroed entries. Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/