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=-15.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 68A6EC433DB for ; Fri, 29 Jan 2021 09:05:28 +0000 (UTC) Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) (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 0D8D264E19 for ; Fri, 29 Jan 2021 09:05:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0D8D264E19 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id 943FA86A54; Fri, 29 Jan 2021 09:05:27 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from fraxinus.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id GIIJ8UMiPAuI; Fri, 29 Jan 2021 09:05:26 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by fraxinus.osuosl.org (Postfix) with ESMTP id 9020086A02; Fri, 29 Jan 2021 09:05:26 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 803B8C0FA7; Fri, 29 Jan 2021 09:05:26 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) by lists.linuxfoundation.org (Postfix) with ESMTP id ACB14C013A for ; Fri, 29 Jan 2021 09:05:24 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id 93BE787490 for ; Fri, 29 Jan 2021 09:05:24 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id oPwrKTlsW7o4 for ; Fri, 29 Jan 2021 09:05:23 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by hemlock.osuosl.org (Postfix) with ESMTPS id 5C2EF872F2 for ; Fri, 29 Jan 2021 09:05:23 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 04F8464E02; Fri, 29 Jan 2021 09:05:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1611911122; bh=/HEREiD9FXEQ02w0iDsYdpZV46bpzXWuTWwUnZCuy+g=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=T2Y4mkH4w077yIZlxHUVZE0D4RLQbzNe5OiDenFlQlsPGBt8ss4Zj5rDF9fgoTP6k xu/Bzo1XE71GsYZvBptwDuXs+wrULWcJy59bKBfcuSW6zcG3ZRJG1gBozI/YJrugAl MMUMZtS57yD2ctcrz9XePHff3N9cgreQyEruAzA8ACCzWDRviQd8aygMSvYmgMRvSG 44NQVC9cG3gE5XfiE0NYf8UuiODbFhBNGAYIMViLeyZGqQOYDg+cJCQNDfEsJDe6dK TV+HEKx68IBMweLIWECiO0hHiD7/CetE8nlx5WYoMeZIT1q53s9cIc6Eou5QJxr8Hl dY2QCJu/TSm3Q== Date: Fri, 29 Jan 2021 09:05:16 +0000 From: Will Deacon To: Sai Prakash Ranjan Subject: Re: [PATCH 2/3] iommu/io-pgtable-arm: Add IOMMU_LLC page protection flag Message-ID: <20210129090516.GB3998@willie-the-truck> References: <3f589e7de3f9fa93e84c83420c5270c546a0c368.1610372717.git.saiprakash.ranjan@codeaurora.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <3f589e7de3f9fa93e84c83420c5270c546a0c368.1610372717.git.saiprakash.ranjan@codeaurora.org> User-Agent: Mutt/1.10.1 (2018-07-13) Cc: isaacm@codeaurora.org, freedreno , David Airlie , linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, Akhil P Oommen , Sean Paul , Kristian H Kristensen , dri-devel@lists.freedesktop.org, Daniel Vetter , linux-arm-msm@vger.kernel.org, Robin Murphy , linux-arm-kernel@lists.infradead.org X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Mon, Jan 11, 2021 at 07:45:04PM +0530, Sai Prakash Ranjan wrote: > Add a new page protection flag IOMMU_LLC which can be used > by non-coherent masters to set cacheable memory attributes > for an outer level of cache called as last-level cache or > system cache. Initial user of this page protection flag is > the adreno gpu and then can later be used by other clients > such as video where this can be used for per-buffer based > mapping. > > Signed-off-by: Sai Prakash Ranjan > --- > drivers/iommu/io-pgtable-arm.c | 3 +++ > include/linux/iommu.h | 6 ++++++ > 2 files changed, 9 insertions(+) > > diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c > index 7439ee7fdcdb..ebe653ef601b 100644 > --- a/drivers/iommu/io-pgtable-arm.c > +++ b/drivers/iommu/io-pgtable-arm.c > @@ -415,6 +415,9 @@ static arm_lpae_iopte arm_lpae_prot_to_pte(struct arm_lpae_io_pgtable *data, > else if (prot & IOMMU_CACHE) > pte |= (ARM_LPAE_MAIR_ATTR_IDX_CACHE > << ARM_LPAE_PTE_ATTRINDX_SHIFT); > + else if (prot & IOMMU_LLC) > + pte |= (ARM_LPAE_MAIR_ATTR_IDX_INC_OCACHE > + << ARM_LPAE_PTE_ATTRINDX_SHIFT); > } > > if (prot & IOMMU_CACHE) > diff --git a/include/linux/iommu.h b/include/linux/iommu.h > index ffaa389ea128..1f82057df531 100644 > --- a/include/linux/iommu.h > +++ b/include/linux/iommu.h > @@ -31,6 +31,12 @@ > * if the IOMMU page table format is equivalent. > */ > #define IOMMU_PRIV (1 << 5) > +/* > + * Non-coherent masters can use this page protection flag to set cacheable > + * memory attributes for only a transparent outer level of cache, also known as > + * the last-level or system cache. > + */ > +#define IOMMU_LLC (1 << 6) On reflection, I'm a bit worried about exposing this because I think it will introduce a mismatched virtual alias with the CPU (we don't even have a MAIR set up for this memory type). Now, we also have that issue for the PTW, but since we always use cache maintenance (i.e. the streaming API) for publishing the page-tables to a non-coheren walker, it works out. However, if somebody expects IOMMU_LLC to be coherent with a DMA API coherent allocation, then they're potentially in for a nasty surprise due to the mismatched outer-cacheability attributes. So I can take patch (1) as a trivial rename, but unfortunately I think this needs more thought before exposing it beyond the PTW. Will _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu