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Thu, 07 Jan 2021 18:09:18 +0000 (UTC) Received: by mail-pj1-x1035.google.com with SMTP id f14so1904085pju.4 for ; Thu, 07 Jan 2021 10:09:18 -0800 (PST) Received: from [10.67.48.230] ([192.19.223.252]) by smtp.googlemail.com with ESMTPSA id 73sm6854065pga.26.2021.01.07.10.09.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 07 Jan 2021 10:09:17 -0800 (PST) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 1862c76b-fb14-45aa-a0fd-001a46af272e DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:autocrypt:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=vw+3fRUkfsBW4QbvQXU0qs0vfRYiwwo/FP9gAc8ddJM=; b=YZm7VyoGVhqHtD1FsmJ/k39LqGH3CzXZDAPcNPkuO69ds5omJ3no6GgI7/xQM878yH 79dDv+LBBMHcj6uk3FYEwQ3pT8yJF7xn+BfZE+PQT60r4Lui6xikZO+W4fl4aYpmym66 5hkhMFywFQPUAJ1ygS0VFd8zxUlyCk9YnpM0oVd8fu2hkvEa/Rq/FpCp4U5avTd+Sogf TTB5LgMS/c6r+Xsk+6+e0Sbj1F+ND0+arqcCA9xYxjOF/cu8Z9lZmhmsHLVus+fkbk0p tC+tYdwsHfWipxuj11enoTlGiF/M1XGCl7Eh0SQNInPpcaJC3PTQs376g2qUfHCytPZA oyOA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:autocrypt :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=vw+3fRUkfsBW4QbvQXU0qs0vfRYiwwo/FP9gAc8ddJM=; b=rpZ6d+7q+ZkPSUNqgV/jidmer9VWLb8yunEzIWyrl/oILAqCHz7Ah5KPRB8EQSytJa YCQJshdnouWJsCXM/cEtx30vWbKCIMSVtt5AVXRrsmmFrgsmElRsLyOE1iQvO7FjKpTj gkKFIaHv7En4pRb9evODVIG8hSy0khj7c55ii035+Oo9TA+tnjkIWtMJpxbuCNG7kj+U LXSChBL1ThqynnLCGjbgTjLVrmGdniYrXrUKMGwIQsdLSzXaelTUyvO7UCeMjT6Q/J9k IbQZ5KO2Ll/629Spl91mfM+3FI69hA6S/34AWKf12SysK281JG48N8ixPeCQvA/r0pPm DZTQ== X-Gm-Message-State: AOAM531iw9pbgfVitd1GCsI3rZL0fhlep0MD4Y8Bb0aUzuvWq4t70pO6 uFgdkrY9XkjM8VRc9UseKZ4= X-Google-Smtp-Source: ABdhPJx1xoy1ym4Tw7x4gRoJsL4200DE01Znf0lWr3Vuy9ojCIaAyzQSqEaRuQMdpfdFepL4c54dig== X-Received: by 2002:a17:90a:398d:: with SMTP id z13mr10369314pjb.1.1610042958180; Thu, 07 Jan 2021 10:09:18 -0800 (PST) Subject: Re: [RFC PATCH v3 2/6] swiotlb: Add restricted DMA pool To: Konrad Rzeszutek Wilk , Claire Chang Cc: Rob Herring , mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, "list@263.net:IOMMU DRIVERS" , Joerg Roedel , joro@8bytes.org, will@kernel.org, Frank Rowand , boris.ostrovsky@oracle.com, jgross@suse.com, sstabellini@kernel.org, Christoph Hellwig , Marek Szyprowski , Robin Murphy , grant.likely@arm.com, xypron.glpk@gmx.de, Thierry Reding , mingo@kernel.org, bauerman@linux.ibm.com, peterz@infradead.org, Greg KH , Saravana Kannan , rafael.j.wysocki@intel.com, heikki.krogerus@linux.intel.com, Andy Shevchenko , rdunlap@infradead.org, dan.j.williams@intel.com, Bartosz Golaszewski , linux-devicetree , lkml , linuxppc-dev@lists.ozlabs.org, "list@263.net:IOMMU DRIVERS" , Joerg Roedel , iommu@lists.linux-foundation.org, xen-devel@lists.xenproject.org, Tomasz Figa , Nicolas Boichat References: <20210106034124.30560-1-tientzu@chromium.org> <20210106034124.30560-3-tientzu@chromium.org> <20210106185241.GA109735@localhost.localdomain> <20210107175740.GA16519@char.us.oracle.com> From: Florian Fainelli Autocrypt: addr=f.fainelli@gmail.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210107175740.GA16519@char.us.oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 1/7/21 9:57 AM, Konrad Rzeszutek Wilk wrote: > On Fri, Jan 08, 2021 at 01:39:18AM +0800, Claire Chang wrote: >> Hi Greg and Konrad, >> >> This change is intended to be non-arch specific. Any arch that lacks DMA access >> control and has devices not behind an IOMMU can make use of it. Could you share >> why you think this should be arch specific? > > The idea behind non-arch specific code is it to be generic. The devicetree > is specific to PowerPC, Sparc, and ARM, and not to x86 - hence it should > be in arch specific code. In premise the same code could be used with an ACPI enabled system with an appropriate service to identify the restricted DMA regions and unlock them. More than 1 architecture requiring this function (ARM and ARM64 are the two I can think of needing this immediately) sort of calls for making the code architecture agnostic since past 2, you need something that scales. There is already code today under kernel/dma/contiguous.c that is only activated on a CONFIG_OF=y && CONFIG_OF_RESERVED_MEM=y system, this is no different. -- Florian