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=-8.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 94E08CA9EB5 for ; Mon, 4 Nov 2019 19:20:20 +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 5963C20869 for ; Mon, 4 Nov 2019 19:20:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="mhE/Skjn" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5963C20869 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 mail.linux-foundation.org (localhost [127.0.0.1]) by mail.linuxfoundation.org (Postfix) with ESMTP id 36B48F0E; Mon, 4 Nov 2019 19:20:20 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 20CF3F04 for ; Mon, 4 Nov 2019 19:20:19 +0000 (UTC) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id AA422A9 for ; Mon, 4 Nov 2019 19:20:18 +0000 (UTC) Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7C1FE2084D; Mon, 4 Nov 2019 19:20:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572895218; bh=cDz9gfK8MWilHlMzVfKaiaO3yX6AZlcXNifxBXP/KPQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mhE/SkjnYFG/Lopp8nsY6/eoCtWw7QPgBqtTjOZnv3vl5GZ96mrg5vhmSoQGXyB6S eq1XJ5bTDlbcsckkim34gvAzLzDRisKi39u9eLEORy4KjaineI029mNNSkesgmPuD2 MoXRNwDLEQ48qQo3a3nJMZmX5UQdFSg3OuVSTd8c= Date: Mon, 4 Nov 2019 19:20:11 +0000 From: Will Deacon To: Robin Murphy Subject: Re: [PATCH v2 06/10] iommu/io-pgtable-arm: Simplify level indexing Message-ID: <20191104192010.GJ24909@willie-the-truck> References: <698173b487383735e470a28e5cca4f9db22703de.1572024120.git.robin.murphy@arm.com> <20191104181722.GF24909@willie-the-truck> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Cc: iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org 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-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.org On Mon, Nov 04, 2019 at 06:36:51PM +0000, Robin Murphy wrote: > On 04/11/2019 18:17, Will Deacon wrote: > > On Fri, Oct 25, 2019 at 07:08:35PM +0100, Robin Murphy wrote: > > > The nature of the LPAE format means that data->pg_shift is always > > > redundant with data->bits_per_level, since they represent the size of a > > > page and the number of PTEs per page respectively, and the size of a PTE > > > is constant. Thus it works out more efficient to only store the latter, > > > and derive the former via a trivial addition where necessary. > > > > > > Signed-off-by: Robin Murphy > > > --- > > > drivers/iommu/io-pgtable-arm.c | 29 +++++++++++++---------------- > > > 1 file changed, 13 insertions(+), 16 deletions(-) > > > > > > diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c > > > index 4b1483eb0ccf..15b4927ce36b 100644 > > > --- a/drivers/iommu/io-pgtable-arm.c > > > +++ b/drivers/iommu/io-pgtable-arm.c > > > @@ -36,10 +36,11 @@ > > > * in a virtual address mapped by the pagetable in d. > > > */ > > > #define ARM_LPAE_LVL_SHIFT(l,d) \ > > > - (((ARM_LPAE_MAX_LEVELS - 1 - (l)) * (d)->bits_per_level) + \ > > > - (d)->pg_shift) > > > + (((ARM_LPAE_MAX_LEVELS - (l)) * (d)->bits_per_level) + \ > > > + ilog2(sizeof(arm_lpae_iopte))) > > > -#define ARM_LPAE_GRANULE(d) (1UL << (d)->pg_shift) > > > +#define ARM_LPAE_GRANULE(d) \ > > > + (sizeof(arm_lpae_iopte) << (d)->bits_per_level) > > > #define ARM_LPAE_PGD_SIZE(d) \ > > > (sizeof(arm_lpae_iopte) << (d)->pgd_bits) > > > @@ -55,9 +56,7 @@ > > > ((1 << ((d)->bits_per_level + ARM_LPAE_PGD_IDX(l,d))) - 1)) > > > /* Calculate the block/page mapping size at level l for pagetable in d. */ > > > -#define ARM_LPAE_BLOCK_SIZE(l,d) \ > > > - (1ULL << (ilog2(sizeof(arm_lpae_iopte)) + \ > > > - ((ARM_LPAE_MAX_LEVELS - (l)) * (d)->bits_per_level))) > > > +#define ARM_LPAE_BLOCK_SIZE(l,d) (1ULL << ARM_LPAE_LVL_SHIFT(l,d)) > > > /* Page table bits */ > > > #define ARM_LPAE_PTE_TYPE_SHIFT 0 > > > @@ -175,8 +174,7 @@ struct arm_lpae_io_pgtable { > > > int pgd_bits; > > > int start_level; > > > - unsigned long pg_shift; > > > - unsigned long bits_per_level; > > > + int bits_per_level; > > > void *pgd; > > > }; > > > @@ -206,7 +204,7 @@ static phys_addr_t iopte_to_paddr(arm_lpae_iopte pte, > > > { > > > u64 paddr = pte & ARM_LPAE_PTE_ADDR_MASK; > > > - if (data->pg_shift < 16) > > > + if (data->bits_per_level < 13) /* i.e. 64K granule */ > > > > nit, but: > > > > if (ARM_LPAE_GRANULE(data) < SZ_64K) > > > > might be clearer and avoid the need for a comment? > > Unfortunately GCC doesn't treat the two as directly equivalent (presumably > due to boundary conditions) so will emit the additional faff to actually > compute and compare the intermediate value every time, rather than just > trivially testing the shift. I figured the minor I$/register pressure win > was worth the small price of a comment. Bet ya can't measure the difference ;) I'd prefer the readable version in the absence of numbers. Will _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu 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=-8.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 E496ACA9EB5 for ; Mon, 4 Nov 2019 19:20:24 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 BF0B020869 for ; Mon, 4 Nov 2019 19:20:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="BRYXrZYZ"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="mhE/Skjn" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BF0B020869 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=DGHucamTh6rAkWAGP/UJz3B8uQYYRiSa0GNc6jPLCuM=; b=BRYXrZYZU9ASg8 D0ABOrclWy526rM6NLFQ0FjYLBFI8bou2dw51SjvJbDQ4luNmc584TQ8nSMWYpBa4azozjur2iWrW 2BC5Xxn/e86WL4+iKrVTKnxSYcgQz7NEPR3KaSRr4TuZGJuhvJI6zv3hH1r958o4oV50LIlJ4TAkD x0aWHRaMV3OwkoYi06y2dPSoLJyqyoanKRLPXiuXy57aw87Ox4f8daUImOoXfoDGRGJ1Sw+r5hwe2 ACepTZQ52AtuwAhCM08PYYbLXOEgfkLt8neHXJtIkT7JNxTTR1B+GW5E7o4RQWeWrIycNReDMXLXP G3jPkbLV7bjFav28+otg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iRhtl-00069v-M3; Mon, 04 Nov 2019 19:20:21 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1iRhti-00069R-UV for linux-arm-kernel@lists.infradead.org; Mon, 04 Nov 2019 19:20:20 +0000 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7C1FE2084D; Mon, 4 Nov 2019 19:20:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572895218; bh=cDz9gfK8MWilHlMzVfKaiaO3yX6AZlcXNifxBXP/KPQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mhE/SkjnYFG/Lopp8nsY6/eoCtWw7QPgBqtTjOZnv3vl5GZ96mrg5vhmSoQGXyB6S eq1XJ5bTDlbcsckkim34gvAzLzDRisKi39u9eLEORy4KjaineI029mNNSkesgmPuD2 MoXRNwDLEQ48qQo3a3nJMZmX5UQdFSg3OuVSTd8c= Date: Mon, 4 Nov 2019 19:20:11 +0000 From: Will Deacon To: Robin Murphy Subject: Re: [PATCH v2 06/10] iommu/io-pgtable-arm: Simplify level indexing Message-ID: <20191104192010.GJ24909@willie-the-truck> References: <698173b487383735e470a28e5cca4f9db22703de.1572024120.git.robin.murphy@arm.com> <20191104181722.GF24909@willie-the-truck> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191104_112019_024236_ADD6DB39 X-CRM114-Status: GOOD ( 23.75 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: iommu@lists.linux-foundation.org, jcrouse@codeaurora.org, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Nov 04, 2019 at 06:36:51PM +0000, Robin Murphy wrote: > On 04/11/2019 18:17, Will Deacon wrote: > > On Fri, Oct 25, 2019 at 07:08:35PM +0100, Robin Murphy wrote: > > > The nature of the LPAE format means that data->pg_shift is always > > > redundant with data->bits_per_level, since they represent the size of a > > > page and the number of PTEs per page respectively, and the size of a PTE > > > is constant. Thus it works out more efficient to only store the latter, > > > and derive the former via a trivial addition where necessary. > > > > > > Signed-off-by: Robin Murphy > > > --- > > > drivers/iommu/io-pgtable-arm.c | 29 +++++++++++++---------------- > > > 1 file changed, 13 insertions(+), 16 deletions(-) > > > > > > diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c > > > index 4b1483eb0ccf..15b4927ce36b 100644 > > > --- a/drivers/iommu/io-pgtable-arm.c > > > +++ b/drivers/iommu/io-pgtable-arm.c > > > @@ -36,10 +36,11 @@ > > > * in a virtual address mapped by the pagetable in d. > > > */ > > > #define ARM_LPAE_LVL_SHIFT(l,d) \ > > > - (((ARM_LPAE_MAX_LEVELS - 1 - (l)) * (d)->bits_per_level) + \ > > > - (d)->pg_shift) > > > + (((ARM_LPAE_MAX_LEVELS - (l)) * (d)->bits_per_level) + \ > > > + ilog2(sizeof(arm_lpae_iopte))) > > > -#define ARM_LPAE_GRANULE(d) (1UL << (d)->pg_shift) > > > +#define ARM_LPAE_GRANULE(d) \ > > > + (sizeof(arm_lpae_iopte) << (d)->bits_per_level) > > > #define ARM_LPAE_PGD_SIZE(d) \ > > > (sizeof(arm_lpae_iopte) << (d)->pgd_bits) > > > @@ -55,9 +56,7 @@ > > > ((1 << ((d)->bits_per_level + ARM_LPAE_PGD_IDX(l,d))) - 1)) > > > /* Calculate the block/page mapping size at level l for pagetable in d. */ > > > -#define ARM_LPAE_BLOCK_SIZE(l,d) \ > > > - (1ULL << (ilog2(sizeof(arm_lpae_iopte)) + \ > > > - ((ARM_LPAE_MAX_LEVELS - (l)) * (d)->bits_per_level))) > > > +#define ARM_LPAE_BLOCK_SIZE(l,d) (1ULL << ARM_LPAE_LVL_SHIFT(l,d)) > > > /* Page table bits */ > > > #define ARM_LPAE_PTE_TYPE_SHIFT 0 > > > @@ -175,8 +174,7 @@ struct arm_lpae_io_pgtable { > > > int pgd_bits; > > > int start_level; > > > - unsigned long pg_shift; > > > - unsigned long bits_per_level; > > > + int bits_per_level; > > > void *pgd; > > > }; > > > @@ -206,7 +204,7 @@ static phys_addr_t iopte_to_paddr(arm_lpae_iopte pte, > > > { > > > u64 paddr = pte & ARM_LPAE_PTE_ADDR_MASK; > > > - if (data->pg_shift < 16) > > > + if (data->bits_per_level < 13) /* i.e. 64K granule */ > > > > nit, but: > > > > if (ARM_LPAE_GRANULE(data) < SZ_64K) > > > > might be clearer and avoid the need for a comment? > > Unfortunately GCC doesn't treat the two as directly equivalent (presumably > due to boundary conditions) so will emit the additional faff to actually > compute and compare the intermediate value every time, rather than just > trivially testing the shift. I figured the minor I$/register pressure win > was worth the small price of a comment. Bet ya can't measure the difference ;) I'd prefer the readable version in the absence of numbers. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel