From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Murphy Subject: Re: [PATCH v5 2/3] iommu/dma: Reserve IOVA for PCIe inaccessible DMA address Date: Thu, 2 May 2019 12:27:02 +0100 Message-ID: <2f4b9492-0caf-d6e3-e727-e3c869eefb58@arm.com> References: <1556732186-21630-1-git-send-email-srinath.mannam@broadcom.com> <1556732186-21630-3-git-send-email-srinath.mannam@broadcom.com> <20190502110152.GA7313@e121166-lin.cambridge.arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190502110152.GA7313@e121166-lin.cambridge.arm.com> Content-Language: en-GB Sender: linux-kernel-owner@vger.kernel.org To: Lorenzo Pieralisi , Srinath Mannam Cc: Bjorn Helgaas , Eric Auger , Joerg Roedel , poza@codeaurora.org, Ray Jui , bcm-kernel-feedback-list@broadcom.com, linux-pci@vger.kernel.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org List-Id: iommu@lists.linux-foundation.org Hi Lorenzo, On 02/05/2019 12:01, Lorenzo Pieralisi wrote: > On Wed, May 01, 2019 at 11:06:25PM +0530, Srinath Mannam wrote: >> dma_ranges field of PCI host bridge structure has resource entries in >> sorted order of address range given through dma-ranges DT property. This >> list is the accessible DMA address range. So that this resource list will >> be processed and reserve IOVA address to the inaccessible address holes in >> the list. >> >> This method is similar to PCI IO resources address ranges reserving in >> IOMMU for each EP connected to host bridge. >> >> Signed-off-by: Srinath Mannam >> Based-on-patch-by: Oza Pawandeep >> Reviewed-by: Oza Pawandeep >> Acked-by: Robin Murphy >> --- >> drivers/iommu/dma-iommu.c | 19 +++++++++++++++++++ >> 1 file changed, 19 insertions(+) >> >> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c >> index 77aabe6..da94844 100644 >> --- a/drivers/iommu/dma-iommu.c >> +++ b/drivers/iommu/dma-iommu.c >> @@ -212,6 +212,7 @@ static void iova_reserve_pci_windows(struct pci_dev *dev, >> struct pci_host_bridge *bridge = pci_find_host_bridge(dev->bus); >> struct resource_entry *window; >> unsigned long lo, hi; >> + phys_addr_t start = 0, end; >> >> resource_list_for_each_entry(window, &bridge->windows) { >> if (resource_type(window->res) != IORESOURCE_MEM) >> @@ -221,6 +222,24 @@ static void iova_reserve_pci_windows(struct pci_dev *dev, >> hi = iova_pfn(iovad, window->res->end - window->offset); >> reserve_iova(iovad, lo, hi); >> } >> + >> + /* Get reserved DMA windows from host bridge */ >> + resource_list_for_each_entry(window, &bridge->dma_ranges) { > > If this list is not sorted it seems to me the logic in this loop is > broken and you can't rely on callers to sort it because it is not a > written requirement and it is not enforced (you know because you > wrote the code but any other developer is not supposed to guess > it). > > Can't we rewrite this loop so that it does not rely on list > entries order ? The original idea was that callers should be required to provide a sorted list, since it keeps things nice and simple... > I won't merge this series unless you sort it, no pun intended. > > Lorenzo > >> + end = window->res->start - window->offset; ...so would you consider it sufficient to add if (end < start) dev_err(...); here, plus commenting the definition of pci_host_bridge::dma_ranges that it must be sorted in ascending order? [ I guess it might even make sense to factor out the parsing and list construction from patch #3 into an of_pci core helper from the beginning, so that there's even less chance of another driver reimplementing it incorrectly in future. ] Failing that, although I do prefer the "simple by construction" approach, I'd have no objection to just sticking a list_sort() call in here instead, if you'd rather it be entirely bulletproof. Robin. >> +resv_iova: >> + if (end - start) { >> + lo = iova_pfn(iovad, start); >> + hi = iova_pfn(iovad, end); >> + reserve_iova(iovad, lo, hi); >> + } >> + start = window->res->end - window->offset + 1; >> + /* If window is last entry */ >> + if (window->node.next == &bridge->dma_ranges && >> + end != ~(dma_addr_t)0) { >> + end = ~(dma_addr_t)0; >> + goto resv_iova; >> + } >> + } >> } >> >> static int iova_reserve_iommu_regions(struct device *dev, >> -- >> 2.7.4 >> 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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 092A3C43219 for ; Thu, 2 May 2019 11:28:12 +0000 (UTC) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id CCDF22075E for ; Thu, 2 May 2019 11:28:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CCDF22075E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from mail.linux-foundation.org (localhost [127.0.0.1]) by mail.linuxfoundation.org (Postfix) with ESMTP id 9FC2730E9; Thu, 2 May 2019 11:28:11 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 25D3830DE for ; Thu, 2 May 2019 11:27:07 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from foss.arm.com (foss.arm.com [217.140.101.70]) by smtp1.linuxfoundation.org (Postfix) with ESMTP id 6D182775 for ; Thu, 2 May 2019 11:27:06 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 074E5A78; Thu, 2 May 2019 04:27:06 -0700 (PDT) Received: from [10.1.196.75] (e110467-lin.cambridge.arm.com [10.1.196.75]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2340C3F719; Thu, 2 May 2019 04:27:03 -0700 (PDT) Subject: Re: [PATCH v5 2/3] iommu/dma: Reserve IOVA for PCIe inaccessible DMA address To: Lorenzo Pieralisi , Srinath Mannam References: <1556732186-21630-1-git-send-email-srinath.mannam@broadcom.com> <1556732186-21630-3-git-send-email-srinath.mannam@broadcom.com> <20190502110152.GA7313@e121166-lin.cambridge.arm.com> From: Robin Murphy Message-ID: <2f4b9492-0caf-d6e3-e727-e3c869eefb58@arm.com> Date: Thu, 2 May 2019 12:27:02 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190502110152.GA7313@e121166-lin.cambridge.arm.com> Content-Language: en-GB Cc: poza@codeaurora.org, Ray Jui , linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, bcm-kernel-feedback-list@broadcom.com, linux-pci@vger.kernel.org, Bjorn Helgaas X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="UTF-8"; format="flowed" Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.org Message-ID: <20190502112702.PJ9tLTDZ3m14hqXLRKrJahY2yHWPVJ1quoevex2rmRQ@z> Hi Lorenzo, On 02/05/2019 12:01, Lorenzo Pieralisi wrote: > On Wed, May 01, 2019 at 11:06:25PM +0530, Srinath Mannam wrote: >> dma_ranges field of PCI host bridge structure has resource entries in >> sorted order of address range given through dma-ranges DT property. This >> list is the accessible DMA address range. So that this resource list will >> be processed and reserve IOVA address to the inaccessible address holes in >> the list. >> >> This method is similar to PCI IO resources address ranges reserving in >> IOMMU for each EP connected to host bridge. >> >> Signed-off-by: Srinath Mannam >> Based-on-patch-by: Oza Pawandeep >> Reviewed-by: Oza Pawandeep >> Acked-by: Robin Murphy >> --- >> drivers/iommu/dma-iommu.c | 19 +++++++++++++++++++ >> 1 file changed, 19 insertions(+) >> >> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c >> index 77aabe6..da94844 100644 >> --- a/drivers/iommu/dma-iommu.c >> +++ b/drivers/iommu/dma-iommu.c >> @@ -212,6 +212,7 @@ static void iova_reserve_pci_windows(struct pci_dev *dev, >> struct pci_host_bridge *bridge = pci_find_host_bridge(dev->bus); >> struct resource_entry *window; >> unsigned long lo, hi; >> + phys_addr_t start = 0, end; >> >> resource_list_for_each_entry(window, &bridge->windows) { >> if (resource_type(window->res) != IORESOURCE_MEM) >> @@ -221,6 +222,24 @@ static void iova_reserve_pci_windows(struct pci_dev *dev, >> hi = iova_pfn(iovad, window->res->end - window->offset); >> reserve_iova(iovad, lo, hi); >> } >> + >> + /* Get reserved DMA windows from host bridge */ >> + resource_list_for_each_entry(window, &bridge->dma_ranges) { > > If this list is not sorted it seems to me the logic in this loop is > broken and you can't rely on callers to sort it because it is not a > written requirement and it is not enforced (you know because you > wrote the code but any other developer is not supposed to guess > it). > > Can't we rewrite this loop so that it does not rely on list > entries order ? The original idea was that callers should be required to provide a sorted list, since it keeps things nice and simple... > I won't merge this series unless you sort it, no pun intended. > > Lorenzo > >> + end = window->res->start - window->offset; ...so would you consider it sufficient to add if (end < start) dev_err(...); here, plus commenting the definition of pci_host_bridge::dma_ranges that it must be sorted in ascending order? [ I guess it might even make sense to factor out the parsing and list construction from patch #3 into an of_pci core helper from the beginning, so that there's even less chance of another driver reimplementing it incorrectly in future. ] Failing that, although I do prefer the "simple by construction" approach, I'd have no objection to just sticking a list_sort() call in here instead, if you'd rather it be entirely bulletproof. Robin. >> +resv_iova: >> + if (end - start) { >> + lo = iova_pfn(iovad, start); >> + hi = iova_pfn(iovad, end); >> + reserve_iova(iovad, lo, hi); >> + } >> + start = window->res->end - window->offset + 1; >> + /* If window is last entry */ >> + if (window->node.next == &bridge->dma_ranges && >> + end != ~(dma_addr_t)0) { >> + end = ~(dma_addr_t)0; >> + goto resv_iova; >> + } >> + } >> } >> >> static int iova_reserve_iommu_regions(struct device *dev, >> -- >> 2.7.4 >> _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu