From patchwork Thu Apr 30 14:34:06 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jean-Philippe Brucker X-Patchwork-Id: 11520563 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3C65B14B4 for ; Thu, 30 Apr 2020 14:43:43 +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 1580F20731 for ; Thu, 30 Apr 2020 14:43:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="NmXdjznk"; dkim=fail reason="signature verification failed" (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="tzcdYYDn" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1580F20731 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linaro.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.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:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=yBPaiZwfvSo4lTHUifiTxP9shHRkrc5CM8JQk0XeDgE=; b=NmXdjznkUA4VkQ jOxLbf8HE2BSFwDU44pv0anGIvnkmGrQ6/i+hPserJ9+YveYS2LNoI7+t4C0XyOszAdb95ZwIC93W irYdTQ60V+8DuNZWgnJqnSOrNTo7jV8boNQ2Zv8vtZB8BlFjcOODN8cHMOeZYZoH00Ho8MktvEIzl 2kvPzmrgtM3WnUj9drSB3IGcCk1+XIX+WzXsEeKGDtJlMdOgfGrLCzrtj6fPK6GuRzTtBkbqL4Xll hxZjXah9amu4A6mY2xJRTcq7y8vbP9d73vFUbdYAQksV4A+HUSbHGqN68Vn9jzy4+d7n4fky3m0cd oJA7EXsGQWohxoVaLw4Q==; 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 1jUAPa-00054A-GA; Thu, 30 Apr 2020 14:43:38 +0000 Received: from mail-wm1-x344.google.com ([2a00:1450:4864:20::344]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jUAMW-0002Os-Dr for linux-arm-kernel@lists.infradead.org; Thu, 30 Apr 2020 14:40:33 +0000 Received: by mail-wm1-x344.google.com with SMTP id r26so2210327wmh.0 for ; Thu, 30 Apr 2020 07:40:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=vSIvSRBzv8F87N2eh+SogoEdQ3Y+F4975ZvmBVJjXyM=; b=tzcdYYDnJJWmpXjOpgnid6d4dTYm6kQVVWfzPSygXZa6oqY8GOtk+I9pkl/978JDwv mQbNf5wE2dcfmDeRArm4tX4AHl4LX8xykzcpixdlo0n8cygHehdL5OENIN71IdjhG1Bt P5sDDS9Bw23exlEa7juXJTL1DFRSKh2611//wdwKe4KEbDPbn0XEg9EmysIRL2+UZx/E XSbQltT/V2GGEtrIWyxkZf7TL9HwlvqktWSG53FRVUwVm+7PdTebAaTHy/vZM7wn8KM3 HDyWenOwxKTUKEIx0B2LW0us/eY7srXkB/4wZtI4oF5HJm951GdLYXXafMEiEfhHBZVo iclw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=vSIvSRBzv8F87N2eh+SogoEdQ3Y+F4975ZvmBVJjXyM=; b=iDMQlFG1zSSsgOSyEU/g1B2I/lgVUvJzC/3gnwoAYE6OjHHfdbjQzelsbar+soxHCU MaDj49o+HVgpa5yZrpdYiBesxEl0rtvUtxQv4obAMYHQbs7l2kiKRi7+A8dFCmzNZsnx kG9TQnA5alIH1bvMHf9PBndvBI8lJ8a3At8DPTV20aXcYMS+CfBmkT5C/7B7bvobJ9xU lKHm88KyLAVw01chpkxCBEq5w1hfclwfKvfBMPKXoEBTB526kuw7/Lk1guq/tCptmjTE r0V2tBn6xmiJlYzrrv7Y4bFyvtUPa8wws/gS5hRECsTU8r3w7+BCYvx3J2EaUaGzmYvg ai7A== X-Gm-Message-State: AGi0PuZdbWZTUX4aPwy4ZggbRD2b5IRN/fLZN+G4fnmkKXyDos6LL05F VZM9tXrpB65P61R5UTPhz8QjoQ== X-Google-Smtp-Source: APiQypILBmgDpVJ3kGkqLumDZa/s/TYeNjreRgbRNmhtdf3KCt9R3YPaJk7ZdU8tHg9mzB6E1vZF2g== X-Received: by 2002:a1c:4e16:: with SMTP id g22mr3202925wmh.157.1588257626712; Thu, 30 Apr 2020 07:40:26 -0700 (PDT) Received: from localhost.localdomain ([2001:171b:226e:c200:c43b:ef78:d083:b355]) by smtp.gmail.com with ESMTPSA id n2sm4153286wrt.33.2020.04.30.07.40.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Apr 2020 07:40:26 -0700 (PDT) From: Jean-Philippe Brucker To: iommu@lists.linux-foundation.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v6 07/25] arm64: mm: Pin down ASIDs for sharing mm with devices Date: Thu, 30 Apr 2020 16:34:06 +0200 Message-Id: <20200430143424.2787566-8-jean-philippe@linaro.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200430143424.2787566-1-jean-philippe@linaro.org> References: <20200430143424.2787566-1-jean-philippe@linaro.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200430_074030_266504_FDE685A5 X-CRM114-Status: GOOD ( 25.51 ) X-Spam-Score: -0.2 (/) X-Spam-Report: SpamAssassin version 3.4.4 on bombadil.infradead.org summary: Content analysis details: (-0.2 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no trust [2a00:1450:4864:20:0:0:0:344 listed in] [list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid 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: fenghua.yu@intel.com, kevin.tian@intel.com, jacob.jun.pan@linux.intel.com, jgg@ziepe.ca, catalin.marinas@arm.com, joro@8bytes.org, robin.murphy@arm.com, hch@infradead.org, zhangfei.gao@linaro.org, Jean-Philippe Brucker , Jonathan.Cameron@huawei.com, felix.kuehling@amd.com, xuzaibo@huawei.com, will@kernel.org, christian.koenig@amd.com, baolu.lu@linux.intel.com Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org To enable address space sharing with the IOMMU, introduce mm_context_get() and mm_context_put(), that pin down a context and ensure that it will keep its ASID after a rollover. Export the symbols to let the modular SMMUv3 driver use them. Pinning is necessary because a device constantly needs a valid ASID, unlike tasks that only require one when running. Without pinning, we would need to notify the IOMMU when we're about to use a new ASID for a task, and it would get complicated when a new task is assigned a shared ASID. Consider the following scenario with no ASID pinned: 1. Task t1 is running on CPUx with shared ASID (gen=1, asid=1) 2. Task t2 is scheduled on CPUx, gets ASID (1, 2) 3. Task tn is scheduled on CPUy, a rollover occurs, tn gets ASID (2, 1) We would now have to immediately generate a new ASID for t1, notify the IOMMU, and finally enable task tn. We are holding the lock during all that time, since we can't afford having another CPU trigger a rollover. The IOMMU issues invalidation commands that can take tens of milliseconds. It gets needlessly complicated. All we wanted to do was schedule task tn, that has no business with the IOMMU. By letting the IOMMU pin tasks when needed, we avoid stalling the slow path, and let the pinning fail when we're out of shareable ASIDs. After a rollover, the allocator expects at least one ASID to be available in addition to the reserved ones (one per CPU). So (NR_ASIDS - NR_CPUS - 1) is the maximum number of ASIDs that can be shared with the IOMMU. Signed-off-by: Jean-Philippe Brucker --- arch/arm64/include/asm/mmu.h | 1 + arch/arm64/include/asm/mmu_context.h | 11 +++- arch/arm64/mm/context.c | 95 +++++++++++++++++++++++++++- 3 files changed, 104 insertions(+), 3 deletions(-) diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h index 68140fdd89d6b..bbdd291e31d59 100644 --- a/arch/arm64/include/asm/mmu.h +++ b/arch/arm64/include/asm/mmu.h @@ -19,6 +19,7 @@ typedef struct { atomic64_t id; + unsigned long pinned; void *vdso; unsigned long flags; } mm_context_t; diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h index ab46187c63001..69599a64945b0 100644 --- a/arch/arm64/include/asm/mmu_context.h +++ b/arch/arm64/include/asm/mmu_context.h @@ -177,7 +177,13 @@ static inline void cpu_replace_ttbr1(pgd_t *pgdp) #define destroy_context(mm) do { } while(0) void check_and_switch_context(struct mm_struct *mm, unsigned int cpu); -#define init_new_context(tsk,mm) ({ atomic64_set(&(mm)->context.id, 0); 0; }) +static inline int +init_new_context(struct task_struct *tsk, struct mm_struct *mm) +{ + atomic64_set(&mm->context.id, 0); + mm->context.pinned = 0; + return 0; +} #ifdef CONFIG_ARM64_SW_TTBR0_PAN static inline void update_saved_ttbr0(struct task_struct *tsk, @@ -250,6 +256,9 @@ switch_mm(struct mm_struct *prev, struct mm_struct *next, void verify_cpu_asid_bits(void); void post_ttbr_update_workaround(void); +unsigned long mm_context_get(struct mm_struct *mm); +void mm_context_put(struct mm_struct *mm); + #endif /* !__ASSEMBLY__ */ #endif /* !__ASM_MMU_CONTEXT_H */ diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c index d702d60e64dab..d0ddd413f5645 100644 --- a/arch/arm64/mm/context.c +++ b/arch/arm64/mm/context.c @@ -27,6 +27,10 @@ static DEFINE_PER_CPU(atomic64_t, active_asids); static DEFINE_PER_CPU(u64, reserved_asids); static cpumask_t tlb_flush_pending; +static unsigned long max_pinned_asids; +static unsigned long nr_pinned_asids; +static unsigned long *pinned_asid_map; + #define ASID_MASK (~GENMASK(asid_bits - 1, 0)) #define ASID_FIRST_VERSION (1UL << asid_bits) @@ -74,6 +78,9 @@ void verify_cpu_asid_bits(void) static void set_kpti_asid_bits(void) { + unsigned int k; + u8 *dst = (u8 *)asid_map; + u8 *src = (u8 *)pinned_asid_map; unsigned int len = BITS_TO_LONGS(NUM_USER_ASIDS) * sizeof(unsigned long); /* * In case of KPTI kernel/user ASIDs are allocated in @@ -81,7 +88,8 @@ static void set_kpti_asid_bits(void) * is set, then the ASID will map only userspace. Thus * mark even as reserved for kernel. */ - memset(asid_map, 0xaa, len); + for (k = 0; k < len; k++) + dst[k] = src[k] | 0xaa; } static void set_reserved_asid_bits(void) @@ -89,7 +97,7 @@ static void set_reserved_asid_bits(void) if (arm64_kernel_unmapped_at_el0()) set_kpti_asid_bits(); else - bitmap_clear(asid_map, 0, NUM_USER_ASIDS); + bitmap_copy(asid_map, pinned_asid_map, NUM_USER_ASIDS); } #define asid_gen_match(asid) \ @@ -165,6 +173,14 @@ static u64 new_context(struct mm_struct *mm) if (check_update_reserved_asid(asid, newasid)) return newasid; + /* + * If it is pinned, we can keep using it. Note that reserved + * takes priority, because even if it is also pinned, we need to + * update the generation into the reserved_asids. + */ + if (mm->context.pinned) + return newasid; + /* * We had a valid ASID in a previous life, so try to re-use * it if possible. @@ -254,6 +270,68 @@ void check_and_switch_context(struct mm_struct *mm, unsigned int cpu) cpu_switch_mm(mm->pgd, mm); } +unsigned long mm_context_get(struct mm_struct *mm) +{ + unsigned long flags; + u64 asid; + + raw_spin_lock_irqsave(&cpu_asid_lock, flags); + + asid = atomic64_read(&mm->context.id); + + if (mm->context.pinned) { + mm->context.pinned++; + asid &= ~ASID_MASK; + goto out_unlock; + } + + if (nr_pinned_asids >= max_pinned_asids) { + asid = 0; + goto out_unlock; + } + + if (!asid_gen_match(asid)) { + /* + * We went through one or more rollover since that ASID was + * used. Ensure that it is still valid, or generate a new one. + */ + asid = new_context(mm); + atomic64_set(&mm->context.id, asid); + } + + asid &= ~ASID_MASK; + + nr_pinned_asids++; + __set_bit(asid2idx(asid), pinned_asid_map); + mm->context.pinned++; + +out_unlock: + raw_spin_unlock_irqrestore(&cpu_asid_lock, flags); + + /* Set the equivalent of USER_ASID_BIT */ + if (asid && IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0)) + asid |= 1; + + return asid; +} +EXPORT_SYMBOL_GPL(mm_context_get); + +void mm_context_put(struct mm_struct *mm) +{ + unsigned long flags; + u64 asid = atomic64_read(&mm->context.id) & ~ASID_MASK; + + raw_spin_lock_irqsave(&cpu_asid_lock, flags); + + if (--mm->context.pinned == 0) { + __clear_bit(asid2idx(asid), pinned_asid_map); + nr_pinned_asids--; + } + + raw_spin_unlock_irqrestore(&cpu_asid_lock, flags); +} +EXPORT_SYMBOL_GPL(mm_context_put); + /* Errata workaround post TTBRx_EL1 update. */ asmlinkage void post_ttbr_update_workaround(void) { @@ -303,6 +381,13 @@ static int asids_update_limit(void) WARN_ON(num_available_asids - 1 <= num_possible_cpus()); pr_info("ASID allocator initialised with %lu entries\n", num_available_asids); + + /* + * We assume that an ASID is always available after a rollover. This + * means that even if all CPUs have a reserved ASID, there still is at + * least one slot available in the asid map. + */ + max_pinned_asids = num_available_asids - num_possible_cpus() - 2; return 0; } arch_initcall(asids_update_limit); @@ -317,6 +402,12 @@ static int asids_init(void) panic("Failed to allocate bitmap for %lu ASIDs\n", NUM_USER_ASIDS); + pinned_asid_map = kcalloc(BITS_TO_LONGS(NUM_USER_ASIDS), + sizeof(*pinned_asid_map), GFP_KERNEL); + if (!pinned_asid_map) + panic("Failed to allocate pinned ASID bitmap\n"); + nr_pinned_asids = 0; + /* * We cannot call set_reserved_asid_bits() here because CPU * caps are not finalized yet, so it is safer to assume KPTI