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=-11.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,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 5E8D6C433E4 for ; Mon, 13 Jul 2020 20:22:46 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1FA5A2075D for ; Mon, 13 Jul 2020 20:22:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="oiFwI26T" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1FA5A2075D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 93CD58D0002; Mon, 13 Jul 2020 16:22:45 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 89E528D0001; Mon, 13 Jul 2020 16:22:45 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 78CC68D0002; Mon, 13 Jul 2020 16:22:45 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0233.hostedemail.com [216.40.44.233]) by kanga.kvack.org (Postfix) with ESMTP id 5DA288D0001 for ; Mon, 13 Jul 2020 16:22:45 -0400 (EDT) Received: from smtpin11.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id D3CAD180AD82F for ; Mon, 13 Jul 2020 20:22:44 +0000 (UTC) X-FDA: 77034175848.11.legs25_230e7ad26eeb Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin11.hostedemail.com (Postfix) with ESMTP id ABA14180F8B82 for ; Mon, 13 Jul 2020 20:22:44 +0000 (UTC) X-HE-Tag: legs25_230e7ad26eeb X-Filterd-Recvd-Size: 6717 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf03.hostedemail.com (Postfix) with ESMTP for ; Mon, 13 Jul 2020 20:22:44 +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 628A52075B; Mon, 13 Jul 2020 20:22:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594671762; bh=tM1FG+INMniDO2N5XmTmfJsq0UrVrFhjB9hPE3JBaRI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=oiFwI26TXEaKYwiXAkSUdtnF6xjknVkYaPt5FiaBfoFvuqmyN4pT7MpgNbZGtVlTf GNimjfAn28yXttkqcq6BhRH+mWq/kz5JNKQYSZyPpswpDRY2/1nb11twItEbbpn7dJ sKniyzq9REWXMHQ55HYbTFFb9Nb/cSJHS3EBb3k0= Date: Mon, 13 Jul 2020 21:22:37 +0100 From: Will Deacon To: Jean-Philippe Brucker Cc: iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, joro@8bytes.org, catalin.marinas@arm.com, robin.murphy@arm.com, baolu.lu@linux.intel.com, Jonathan.Cameron@huawei.com, jacob.jun.pan@linux.intel.com, zhangfei.gao@linaro.org, xuzaibo@huawei.com, zhengxiang9@huawei.com, fenghua.yu@intel.com, hch@infradead.org, Suzuki K Poulose Subject: Re: [PATCH v8 07/12] iommu/arm-smmu-v3: Share process page tables Message-ID: <20200713202236.GA3575@willie-the-truck> References: <20200618155125.1548969-1-jean-philippe@linaro.org> <20200618155125.1548969-8-jean-philippe@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200618155125.1548969-8-jean-philippe@linaro.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspamd-Queue-Id: ABA14180F8B82 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam01 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jun 18, 2020 at 05:51:20PM +0200, Jean-Philippe Brucker wrote: > With Shared Virtual Addressing (SVA), we need to mirror CPU TTBR, TCR, > MAIR and ASIDs in SMMU contexts. Each SMMU has a single ASID space split > into two sets, shared and private. Shared ASIDs correspond to those > obtained from the arch ASID allocator, and private ASIDs are used for > "classic" map/unmap DMA. > > A possible conflict happens when trying to use a shared ASID that has > already been allocated for private use by the SMMU driver. This will be > addressed in a later patch by replacing the private ASID. At the > moment we return -EBUSY. > > Each mm_struct shared with the SMMU will have a single context > descriptor. Add a refcount to keep track of this. It will be protected > by the global SVA lock. > > Acked-by: Suzuki K Poulose > Signed-off-by: Jean-Philippe Brucker > --- > drivers/iommu/arm-smmu-v3.c | 150 +++++++++++++++++++++++++++++++++++- > 1 file changed, 146 insertions(+), 4 deletions(-) > > diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c > index 937aa1af428d5..cabd942e4cbf3 100644 > --- a/drivers/iommu/arm-smmu-v3.c > +++ b/drivers/iommu/arm-smmu-v3.c > @@ -22,6 +22,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -33,6 +34,8 @@ > > #include > > +#include "io-pgtable-arm.h" > + > /* MMIO registers */ > #define ARM_SMMU_IDR0 0x0 > #define IDR0_ST_LVL GENMASK(28, 27) > @@ -589,6 +592,9 @@ struct arm_smmu_ctx_desc { > u64 ttbr; > u64 tcr; > u64 mair; > + > + refcount_t refs; > + struct mm_struct *mm; > }; > > struct arm_smmu_l1_ctx_desc { > @@ -727,6 +733,7 @@ struct arm_smmu_option_prop { > }; > > static DEFINE_XARRAY_ALLOC1(asid_xa); > +static DEFINE_MUTEX(sva_lock); > > static struct arm_smmu_option_prop arm_smmu_options[] = { > { ARM_SMMU_OPT_SKIP_PREFETCH, "hisilicon,broken-prefetch-cmd" }, > @@ -1662,7 +1669,8 @@ static int arm_smmu_write_ctx_desc(struct arm_smmu_domain *smmu_domain, > #ifdef __BIG_ENDIAN > CTXDESC_CD_0_ENDI | > #endif > - CTXDESC_CD_0_R | CTXDESC_CD_0_A | CTXDESC_CD_0_ASET | > + CTXDESC_CD_0_R | CTXDESC_CD_0_A | > + (cd->mm ? 0 : CTXDESC_CD_0_ASET) | > CTXDESC_CD_0_AA64 | > FIELD_PREP(CTXDESC_CD_0_ASID, cd->asid) | > CTXDESC_CD_0_V; > @@ -1766,12 +1774,144 @@ static void arm_smmu_free_cd_tables(struct arm_smmu_domain *smmu_domain) > cdcfg->cdtab = NULL; > } > > -static void arm_smmu_free_asid(struct arm_smmu_ctx_desc *cd) > +static void arm_smmu_init_cd(struct arm_smmu_ctx_desc *cd) > { > + refcount_set(&cd->refs, 1); > +} > + > +static bool arm_smmu_free_asid(struct arm_smmu_ctx_desc *cd) > +{ > + bool free; > + struct arm_smmu_ctx_desc *old_cd; > + > if (!cd->asid) > - return; > + return false; > + > + free = refcount_dec_and_test(&cd->refs); > + if (free) { > + old_cd = xa_erase(&asid_xa, cd->asid); > + WARN_ON(old_cd != cd); > + } > + return free; > +} > + > +static struct arm_smmu_ctx_desc *arm_smmu_share_asid(u16 asid) > +{ > + struct arm_smmu_ctx_desc *cd; > > - xa_erase(&asid_xa, cd->asid); > + cd = xa_load(&asid_xa, asid); > + if (!cd) > + return NULL; > + > + if (cd->mm) { > + /* All devices bound to this mm use the same cd struct. */ > + refcount_inc(&cd->refs); > + return cd; > + } How do you handle racing against a concurrent arm_smmu_free_asid() here? > +__maybe_unused > +static struct arm_smmu_ctx_desc *arm_smmu_alloc_shared_cd(struct mm_struct *mm) > +{ > + u16 asid; > + int ret = 0; > + u64 tcr, par, reg; > + struct arm_smmu_ctx_desc *cd; > + struct arm_smmu_ctx_desc *old_cd = NULL; > + > + lockdep_assert_held(&sva_lock); Please don't bother with these for static functions (but I can see the value in having them for functions with external callers). > + > + asid = mm_context_get(mm); > + if (!asid) > + return ERR_PTR(-ESRCH); > + > + cd = kzalloc(sizeof(*cd), GFP_KERNEL); > + if (!cd) { > + ret = -ENOMEM; > + goto err_put_context; > + } > + > + arm_smmu_init_cd(cd); > + > + old_cd = arm_smmu_share_asid(asid); > + if (IS_ERR(old_cd)) { > + ret = PTR_ERR(old_cd); > + goto err_free_cd; > + } else if (old_cd) { Don't need the 'else' > + if (WARN_ON(old_cd->mm != mm)) { > + ret = -EINVAL; > + goto err_free_cd; > + } > + kfree(cd); > + mm_context_put(mm); > + return old_cd; This is a bit messy. Can you consolidate the return path so that ret is a pointer and you have an 'int err', e.g.: return err < 0 ? ERR_PTR(err) : ret; Will