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 2DF06C433F5 for ; Wed, 5 Jan 2022 09:07:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238756AbiAEJH0 (ORCPT ); Wed, 5 Jan 2022 04:07:26 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:28285 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238747AbiAEJHV (ORCPT ); Wed, 5 Jan 2022 04:07:21 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1641373641; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=zLHo5gatlAz4K5AXtvrHLogJItKyAj7DCmCIcRo2WqU=; b=WYEfu7A8sB0UTmKWDonhEIlrZQQGlmEeFf6OjYC1X/wUwZGE0Yfs/I9gp+SP9Jg8eNexmq J4S5CboVXz1pg20++okdfxAiUKU6aGdShEsS8O1UCkCc196wcA54ZCRZiIwNxWHkmvh3pg fvqlnZCoU6Qrz2aNvAVTn6FCOV2zAXg= Received: from mail-pg1-f198.google.com (mail-pg1-f198.google.com [209.85.215.198]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-345-3nxHPzGXMMKCyNl2eFBT8g-1; Wed, 05 Jan 2022 04:07:17 -0500 X-MC-Unique: 3nxHPzGXMMKCyNl2eFBT8g-1 Received: by mail-pg1-f198.google.com with SMTP id c75-20020a63354e000000b003408e4153d1so21124829pga.9 for ; Wed, 05 Jan 2022 01:07:17 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=zLHo5gatlAz4K5AXtvrHLogJItKyAj7DCmCIcRo2WqU=; b=LKbO+8c01mC7MeYRVcm0sUZQlfb9DiK3bvi6j8Axz3+GdoprkeSkSaOdlgT3lld5un igFEdVqmBtkZtaNlDUd39kNEPzHIBSBzq4hGq54BxpvPMOWnCOx16NSwh5ye3nQvYWqx i2SF9lRJ/19EMxnY20OvDVpjdWHog1btyQlQOm6ffVW5Qozgk0ik93t3A+gg96dpTnuu klypCWG5+JqkyraE2KpXJNH3JrC5EkkBRKM0mcV+2Jf6alWGhM29UsBC/3bqeYstuwvD nfNA8WJgR7L8vAMP1xLd1VXRCTWvyCURuApTJxhCrOZK3ASWtiji+iP5hPUuMfyf9qLK Nrtw== X-Gm-Message-State: AOAM532zMmjZwIzixeX67R5w0+qmKa96kDeM6bv1EKwwBda6B6NmvH4I L6wDzoW02/Lxd1MRrmvKPLblwkvZOg+u63kX6CVxHUsMzokPNorHtktU+V7BrJgg2ooqpEjjwJn uIka9NzsA0m8kay2YsGvaX37K X-Received: by 2002:a17:90a:ff17:: with SMTP id ce23mr2935539pjb.164.1641373636637; Wed, 05 Jan 2022 01:07:16 -0800 (PST) X-Google-Smtp-Source: ABdhPJygM2moouakshCbTCfB6/j7aKotwHT4x7eDd+T3cw/smwNCpvmGYdchc35/8RBcj8F/v0HOrQ== X-Received: by 2002:a17:90a:ff17:: with SMTP id ce23mr2935527pjb.164.1641373636403; Wed, 05 Jan 2022 01:07:16 -0800 (PST) Received: from xz-m1.local ([191.101.132.50]) by smtp.gmail.com with ESMTPSA id g5sm47343621pfj.143.2022.01.05.01.07.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Jan 2022 01:07:15 -0800 (PST) Date: Wed, 5 Jan 2022 17:07:10 +0800 From: Peter Xu To: Nikunj A Dadhania Cc: Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, vasant.hegde@amd.com, brijesh.singh@amd.com Subject: Re: [PATCH v2] KVM: x86: Check for rmaps allocation Message-ID: References: <20220105040337.4234-1-nikunj@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20220105040337.4234-1-nikunj@amd.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 05, 2022 at 09:33:37AM +0530, Nikunj A Dadhania wrote: > With TDP MMU being the default now, access to mmu_rmaps_stat debugfs > file causes following oops: > > BUG: kernel NULL pointer dereference, address: 0000000000000000 > PGD 0 P4D 0 > Oops: 0000 [#1] PREEMPT SMP NOPTI > CPU: 7 PID: 3185 Comm: cat Not tainted 5.16.0-rc4+ #204 > RIP: 0010:pte_list_count+0x6/0x40 > Call Trace: > > ? kvm_mmu_rmaps_stat_show+0x15e/0x320 > seq_read_iter+0x126/0x4b0 > ? aa_file_perm+0x124/0x490 > seq_read+0xf5/0x140 > full_proxy_read+0x5c/0x80 > vfs_read+0x9f/0x1a0 > ksys_read+0x67/0xe0 > __x64_sys_read+0x19/0x20 > do_syscall_64+0x3b/0xc0 > entry_SYSCALL_64_after_hwframe+0x44/0xae > RIP: 0033:0x7fca6fc13912 > > Return early when rmaps are not present. > > Reported-by: Vasant Hegde > Tested-by: Vasant Hegde > Signed-off-by: Nikunj A Dadhania > --- > > v1: https://lore.kernel.org/kvm/20220104092814.11553-1-nikunj@amd.com/T/#u > > Check the rmaps inside kvm_mmu_rmaps_stat_show() as the rmaps can be > allocated dynamically (Peter Xu) > > arch/x86/kvm/debugfs.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/x86/kvm/debugfs.c b/arch/x86/kvm/debugfs.c > index 543a8c04025c..9240b3b7f8dd 100644 > --- a/arch/x86/kvm/debugfs.c > +++ b/arch/x86/kvm/debugfs.c > @@ -95,6 +95,9 @@ static int kvm_mmu_rmaps_stat_show(struct seq_file *m, void *v) > unsigned int *log[KVM_NR_PAGE_SIZES], *cur; > int i, j, k, l, ret; > > + if (!kvm_memslots_have_rmaps(kvm)) > + return 0; > + > ret = -ENOMEM; > memset(log, 0, sizeof(log)); > for (i = 0; i < KVM_NR_PAGE_SIZES; i++) { > -- > 2.32.0 > Reviewed-by: Peter Xu Thanks, -- Peter Xu