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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 59A3FC433EF for ; Wed, 23 Feb 2022 05:26:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238337AbiBWF0s (ORCPT ); Wed, 23 Feb 2022 00:26:48 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57808 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238330AbiBWFZm (ORCPT ); Wed, 23 Feb 2022 00:25:42 -0500 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EC4646D953 for ; Tue, 22 Feb 2022 21:24:48 -0800 (PST) Received: by mail-yb1-xb4a.google.com with SMTP id i205-20020a2522d6000000b00622c778ac7cso26758116ybi.3 for ; Tue, 22 Feb 2022 21:24:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=eHvI/S5CbFiuxrTOsf9OKECf8MKQA40+sVHVsgBWXTI=; b=V0N2AQ61NCzV6BZmqiQxUYs5pGX63pZ6VVRWlptLLGQUiVMxzlkVsCzNfrYnsMXVug KGkm/PYQEu9If/h+TwyTP773A843C1vccvswNpzQzC+CWF0lyH9rv4lYVpwygBHxjjxF KtfQ48TD03/CH3MJc6uQdii7U/orjcd6yROvM49vbkxsBatJT7hHIeSSgYOHhBpNRFtZ ikDCPeVq4k3/1dGPRt9rMDvqd7qp2qvlw0rdUxHJz6cMzz6PpmzwFKFFGSl65Hota3P/ hcaYP68KMD05XrecJbTtx+liHxuoMDRkdxyvRDaTUelX+R7q43SiNNrm4qp+y/niXgLp +m3g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=eHvI/S5CbFiuxrTOsf9OKECf8MKQA40+sVHVsgBWXTI=; b=t/0XFCQpQntOWvt0UpdJ0ZxaqKnq2n+1Hu0sEBqQGyfC14DYrht2kNdgyWC13JJIt9 iWm+MX2EiL/sfeNFrceTh1afSlfbeKtDSUUjW9j+t0MOeNguuirlUnYuajsXHDMOax2d io9DWdS7wy4J7420iGzgT1Lc2IZs3rwopf9x20QTKeyqMXzaq7ki1HL608n92hAhlN+s CpRbuN9Air5RKwYm8aXW5u8MhfeD4d3zEZNq1OtSd9aQgx8JJwC8qEtb0I3oQIcmKCPe 6Foo9GQOwZga5qWxlZYwvb/vx4Mb/K0BUHMjS1Mkiy+CdDslXNuxn0fMG1qzUxLXN7yq bjQg== X-Gm-Message-State: AOAM531ijgeESWaFaNVBySC8+dB077H0FdIRZclQp1XFdBW7anJkLbLr te9zd0xC2hEohnjtF3oAxAmChbEuuRL4fua/VBvqKdojroUKDMngCUL37B9A+3FzInbtwOl5BQ4 p53XlT7haBcpWe24QvxSbdURxBXHpAvB5qNOU+Pv0H5dYLKK2/dp8XcBKK12ppjPGNmXTuzgX X-Google-Smtp-Source: ABdhPJylISnqnK8ITQ9nblGksWK/PwAayD9axmVlFF61BCPqFWoHn9afvvtl0MNwA3JR60UblOXBCmfjIzzy X-Received: from js-desktop.svl.corp.google.com ([2620:15c:2cd:202:ccbe:5d15:e2e6:322]) (user=junaids job=sendgmr) by 2002:a81:7951:0:b0:2d6:b7bf:216a with SMTP id u78-20020a817951000000b002d6b7bf216amr24436525ywc.258.1645593874907; Tue, 22 Feb 2022 21:24:34 -0800 (PST) Date: Tue, 22 Feb 2022 21:21:58 -0800 In-Reply-To: <20220223052223.1202152-1-junaids@google.com> Message-Id: <20220223052223.1202152-23-junaids@google.com> Mime-Version: 1.0 References: <20220223052223.1202152-1-junaids@google.com> X-Mailer: git-send-email 2.35.1.473.g83b2b277ed-goog Subject: [RFC PATCH 22/47] mm: asi: Added refcounting when initilizing an asi From: Junaid Shahid To: linux-kernel@vger.kernel.org Cc: Ofir Weisse , kvm@vger.kernel.org, pbonzini@redhat.com, jmattson@google.com, pjt@google.com, alexandre.chartre@oracle.com, rppt@linux.ibm.com, dave.hansen@linux.intel.com, peterz@infradead.org, tglx@linutronix.de, luto@kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ofir Weisse Some KVM tests initilize multiple VMs in a single process. For these cases, we want to suppurt multiple callse to asi_init() before a single asi_destroy is called. We want the initilization to happen exactly once. IF asi_destroy() is called, release the resources only if the counter reached zero. In our current implementation, asi's are tied to a specific mm. This may change in a future implementation. In which case, the mutex for the refcounting will need to move to struct asi. Signed-off-by: Ofir Weisse --- arch/x86/include/asm/asi.h | 1 + arch/x86/mm/asi.c | 52 +++++++++++++++++++++++++++++++++----- include/linux/mm_types.h | 2 ++ kernel/fork.c | 3 +++ 4 files changed, 51 insertions(+), 7 deletions(-) diff --git a/arch/x86/include/asm/asi.h b/arch/x86/include/asm/asi.h index e3cbf6d8801e..2dc465f78bcc 100644 --- a/arch/x86/include/asm/asi.h +++ b/arch/x86/include/asm/asi.h @@ -40,6 +40,7 @@ struct asi { pgd_t *pgd; struct asi_class *class; struct mm_struct *mm; + int64_t asi_ref_count; }; DECLARE_PER_CPU_ALIGNED(struct asi_state, asi_cpu_state); diff --git a/arch/x86/mm/asi.c b/arch/x86/mm/asi.c index 91e5ff1224ff..ac35323193a3 100644 --- a/arch/x86/mm/asi.c +++ b/arch/x86/mm/asi.c @@ -282,9 +282,25 @@ static int __init asi_global_init(void) } subsys_initcall(asi_global_init) +/* We're assuming we hold mm->asi_init_lock */ +static void __asi_destroy(struct asi *asi) +{ + if (!boot_cpu_has(X86_FEATURE_ASI)) + return; + + /* If refcount is non-zero, it means asi_init() was called multiple + * times. We free the asi pgd only when the last VM is destroyed. */ + if (--(asi->asi_ref_count) > 0) + return; + + asi_free_pgd(asi); + memset(asi, 0, sizeof(struct asi)); +} + int asi_init(struct mm_struct *mm, int asi_index, struct asi **out_asi) { - struct asi *asi = &mm->asi[asi_index]; + int err = 0; + struct asi *asi = &mm->asi[asi_index]; *out_asi = NULL; @@ -295,6 +311,15 @@ int asi_init(struct mm_struct *mm, int asi_index, struct asi **out_asi) WARN_ON(asi_index == 0 || asi_index >= ASI_MAX_NUM); WARN_ON(asi->pgd != NULL); + /* Currently, mm and asi structs are conceptually tied together. In + * future implementations an asi object might be unrelated to a specicic + * mm. In that future implementation - the mutex will have to be inside + * asi. */ + mutex_lock(&mm->asi_init_lock); + + if (asi->asi_ref_count++ > 0) + goto exit_unlock; /* err is 0 */ + /* * For now, we allocate 2 pages to avoid any potential problems with * KPTI code. This won't be needed once KPTI is folded into the ASI @@ -302,8 +327,10 @@ int asi_init(struct mm_struct *mm, int asi_index, struct asi **out_asi) */ asi->pgd = (pgd_t *)__get_free_pages(GFP_PGTABLE_USER, PGD_ALLOCATION_ORDER); - if (!asi->pgd) - return -ENOMEM; + if (!asi->pgd) { + err = -ENOMEM; + goto exit_unlock; + } asi->class = &asi_class[asi_index]; asi->mm = mm; @@ -328,19 +355,30 @@ int asi_init(struct mm_struct *mm, int asi_index, struct asi **out_asi) set_pgd(asi->pgd + i, asi_global_nonsensitive_pgd[i]); } - *out_asi = asi; +exit_unlock: + if (err) + __asi_destroy(asi); - return 0; + /* This unlock signals future asi_init() callers that we finished. */ + mutex_unlock(&mm->asi_init_lock); + + if (!err) + *out_asi = asi; + return err; } EXPORT_SYMBOL_GPL(asi_init); void asi_destroy(struct asi *asi) { + struct mm_struct *mm; + if (!boot_cpu_has(X86_FEATURE_ASI) || !asi) return; - asi_free_pgd(asi); - memset(asi, 0, sizeof(struct asi)); + mm = asi->mm; + mutex_lock(&mm->asi_init_lock); + __asi_destroy(asi); + mutex_unlock(&mm->asi_init_lock); } EXPORT_SYMBOL_GPL(asi_destroy); diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index f9702d070975..e6980ae31323 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -16,6 +16,7 @@ #include #include #include +#include #include #include @@ -628,6 +629,7 @@ struct mm_struct { * these resources for every mm in the system, we expect that * only VM mm's will have this flag set. */ bool asi_enabled; + struct mutex asi_init_lock; #endif struct user_namespace *user_ns; diff --git a/kernel/fork.c b/kernel/fork.c index dd5a86e913ea..68b3aeab55ac 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1084,6 +1084,9 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, mm->user_ns = get_user_ns(user_ns); +#ifdef CONFIG_ADDRESS_SPACE_ISOLATION + mutex_init(&mm->asi_init_lock); +#endif return mm; fail_noasi: -- 2.35.1.473.g83b2b277ed-goog