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 6594FC7EE2A for ; Fri, 2 Jun 2023 15:09:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236457AbjFBPJR (ORCPT ); Fri, 2 Jun 2023 11:09:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58548 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236439AbjFBPJL (ORCPT ); Fri, 2 Jun 2023 11:09:11 -0400 Received: from mail-pg1-x54a.google.com (mail-pg1-x54a.google.com [IPv6:2607:f8b0:4864:20::54a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1A3701B7 for ; Fri, 2 Jun 2023 08:09:10 -0700 (PDT) Received: by mail-pg1-x54a.google.com with SMTP id 41be03b00d2f7-53f460cd829so1020680a12.1 for ; Fri, 02 Jun 2023 08:09:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1685718549; x=1688310549; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=Nm6pXa+HYoxt2r3AeUI919wrQrfzAxz3+IaYjnh25eI=; b=CR6zAayusmivzJXEJTT4xo41SprWgGVKmqxFpPcnXXCOZwv7rQ9YKugBL49IUmT5H/ PXmEs2DPAZMaS5HhhZJNSemLJtYyT8LFyswtbyKobbyBSQbTUfYwPaWZucrdpIHB8+c4 SLyxcE4ec5RHEi3fRT1aB/W8mhIACorI2bWFhs5OWRBJ76EkoLy/6OsSnETFnMXt8LAe m5EUq+h3s0MoRf31rqQh7zeEaNqNc1hchJ9rOYTXf3a3HKjTr+jqZ2Lp+657W1rE58AT gYnO93OXQM7Qx9RQvDEV4jqFXRVNQU5JUNumZCgMzg+MMzETwv6b3lf8tAxd5C9lQ+ZK Hs4A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1685718549; x=1688310549; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Nm6pXa+HYoxt2r3AeUI919wrQrfzAxz3+IaYjnh25eI=; b=Rw7jRz59TKB66oNn1pSJyxAMK58gzOOeLkNqKy0uSk6koW/QkdxvKAok/fVCDbPVB4 iGjxvvSEqIA0Pby2isQAkOjcVq3rxFbTkn9jqNEkWUmHaTRJm+p2AqgdwsOj2ZHlAoSQ lUeCB+89bwHZK7GLeJqYhDLSsvSjJCfrnR+1LGfskEygYKIr/hBokUozXygPgZw0M54C l/Sn//UU9hJZJcBS7TBWEHHheVia405jA7jvlL6a0Ng1Vv0cqJ82JXwhKdqCUb0VSZvE J4CtyuMe0tnNnyvpLn8BynzV5h/7Da85ij0KuKaxTrXULDFQqISpvf3sJ7KKHhTi6AsP 3uCA== X-Gm-Message-State: AC+VfDwiu2PPjsx7SjMeNkoyC6zMtb2sO+NKGC0KPGdGmFh57bZa/DUw OwjPhWQ1h1gsXTFOMZajfiXi1jTLwfI= X-Google-Smtp-Source: ACHHUZ7ehZqOGi5yJHK/JvfEtptjcWfG6fH6aJR6XDnDzGuMkl2AI1NWWTXlsI4ACXb4SljxOgCrMzGnjr4= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a63:5f16:0:b0:52c:8878:65dd with SMTP id t22-20020a635f16000000b0052c887865ddmr2374005pgb.0.1685718549518; Fri, 02 Jun 2023 08:09:09 -0700 (PDT) Date: Fri, 2 Jun 2023 08:09:07 -0700 In-Reply-To: <28bd9d11-282f-bb22-66f5-d3d9165d4adf@gmail.com> Mime-Version: 1.0 References: <20230602005859.784190-1-seanjc@google.com> <28bd9d11-282f-bb22-66f5-d3d9165d4adf@gmail.com> Message-ID: Subject: Re: [PATCH] KVM: x86/mmu: Add "never" option to allow sticky disabling of nx_huge_pages From: Sean Christopherson To: Robert Hoo Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Li RongQing , Yong He , Kai Huang Content-Type: text/plain; charset="us-ascii" Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, Jun 02, 2023, Robert Hoo wrote: > On 6/2/2023 8:58 AM, Sean Christopherson wrote: > > @@ -6860,15 +6871,29 @@ static int set_nx_huge_pages(const char *val, const struct kernel_param *kp) > > bool old_val = nx_huge_pages; > > bool new_val; > > + if (nx_hugepage_mitigation_hard_disabled) > > + return -EPERM; > > + > > /* In "auto" mode deploy workaround only if CPU has the bug. */ > > - if (sysfs_streq(val, "off")) > > + if (sysfs_streq(val, "off")) { > > new_val = 0; > > - else if (sysfs_streq(val, "force")) > > + } else if (sysfs_streq(val, "force")) { > > new_val = 1; > > - else if (sysfs_streq(val, "auto")) > > + } else if (sysfs_streq(val, "auto")) { > > new_val = get_nx_auto_mode(); > > - else if (kstrtobool(val, &new_val) < 0) > > + } else if (sysfs_streq(val, "never")) { > > + new_val = 0; > > + > > + mutex_lock(&kvm_lock); > > + if (!list_empty(&vm_list)) { > > + mutex_unlock(&kvm_lock); > > + return -EBUSY; > > + } > > + nx_hugepage_mitigation_hard_disabled = true; > > + mutex_unlock(&kvm_lock); > > + } else if (kstrtobool(val, &new_val) < 0) { > > return -EINVAL; > > + } > > > > IIUC, (Initially) "auto_off"/"off" --> create some VM --> turn to "never", > the created VMs still have those kthreads, but can never be used, until > destroyed with VM. Shouldn't be able to happen. The above rejects "never" if vm_list isn't empty, i.e. if there are any VMs, and sets nx_hugepage_mitigation_hard_disabled under kvm_lock to ensure it can't race with KVM_CREATE_VM. I forgot to call this out in the changelog though.