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 26E87C63797 for ; Thu, 12 Jan 2023 23:30:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232661AbjALXaB (ORCPT ); Thu, 12 Jan 2023 18:30:01 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42944 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232172AbjALXaA (ORCPT ); Thu, 12 Jan 2023 18:30:00 -0500 Received: from mail-pf1-x433.google.com (mail-pf1-x433.google.com [IPv6:2607:f8b0:4864:20::433]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2C699544F2 for ; Thu, 12 Jan 2023 15:29:59 -0800 (PST) Received: by mail-pf1-x433.google.com with SMTP id a30so14953535pfr.6 for ; Thu, 12 Jan 2023 15:29:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=SHCvT7wXhmjcdrY7ZciTjWwkM6hHEFK0c3kr7hoBtAI=; b=ctCtdF94uRfNtxj/svWJF4NSsYdcvFve3xy3/rA8RydeTZ7UjWoTdqG7u996S2CKI/ TehMGCzH40R8wzRHE6l/Qg7QIpGqgUVlPVx5uj/NZKO5kr67dJpoaxvPHITVJXyFOLHv XI3GC6OsKxboq+O8C/C5L6uBMgxgdkOV1ixRpFq9POB1J6aJKL1Uv59KlorrracbhXqB 8typO4QQIPx+dtHB1y8GmaHatYoZsRzusYcwur5NGt7FKgqOdZb2xyUU4Agsx6TE09Wv rHhRLzbjoiEUBC8V4zaAkLFmE/QRWlPIeog/ftIYZCpg54BM2sFvRygIwk8+bRY8eR4u eCug== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=SHCvT7wXhmjcdrY7ZciTjWwkM6hHEFK0c3kr7hoBtAI=; b=XTm8cmogIXahhUzxt7oTrVOyPqckb5/e771oBufxzZcBcN2MwkiQcRR7EZzhhekWXR eQPfcJuSKsE98FAImck7YVM4ts5o69GtBNaUB+mM5vvf2rB0zXdEBXzUIrmB/1DBiAuF jy1RBqd5FayDmAQzkSy5fcvLt89MswW4xEj5xTyg9mUt2YGX8zkH/kVtOFJ8DExivywy NjzRMJYiGVLSaLaJppYqLAV5X3iNSGnBMeERTY/tZBoN9OKdy6VUeJonTXiirwavLaLj /yFRdy9g9zzik1m10yvh9jxAO3td26puHwCt2/OOfY1O8g7OL+rSuYAx6RybjvLmV7Sr af/g== X-Gm-Message-State: AFqh2kqfKBqUqXfyiT1tM/wP19BO9NqxTBOWSIVUjyoTWIHXiqnvbMRj T2UR3i55hUv6NcCFufD1+YO5DA== X-Google-Smtp-Source: AMrXdXtbHXwlb7QCOirDHbnB+4X6BOCeHXpVkWh3Dab4zeJLYVt/vQh0K+r8OkjQmzQev1L+tq2hCQ== X-Received: by 2002:a05:6a00:4514:b0:574:8995:c0d0 with SMTP id cw20-20020a056a00451400b005748995c0d0mr1044208pfb.1.1673566198371; Thu, 12 Jan 2023 15:29:58 -0800 (PST) Received: from google.com (7.104.168.34.bc.googleusercontent.com. [34.168.104.7]) by smtp.gmail.com with ESMTPSA id m190-20020a6258c7000000b005821c109cebsm7829231pfb.199.2023.01.12.15.29.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Jan 2023 15:29:56 -0800 (PST) Date: Thu, 12 Jan 2023 23:29:53 +0000 From: Sean Christopherson To: Matthew Rosato Cc: Alex Williamson , pbonzini@redhat.com, jgg@nvidia.com, cohuck@redhat.com, farman@linux.ibm.com, pmorel@linux.ibm.com, borntraeger@linux.ibm.com, frankja@linux.ibm.com, imbrenda@linux.ibm.com, david@redhat.com, akrowiak@linux.ibm.com, jjherne@linux.ibm.com, pasic@linux.ibm.com, zhenyuw@linux.intel.com, zhi.a.wang@intel.com, linux-s390@vger.kernel.org, kvm@vger.kernel.org, intel-gvt-dev@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] vfio: fix potential deadlock on vfio group lock Message-ID: References: <20230112203844.41179-1-mjrosato@linux.ibm.com> <20230112140517.6db5b346.alex.williamson@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Jan 12, 2023, Matthew Rosato wrote: > On 1/12/23 4:05 PM, Alex Williamson wrote: > > On Thu, 12 Jan 2023 15:38:44 -0500 > > Matthew Rosato wrote: > >> @@ -344,6 +345,35 @@ static bool vfio_assert_device_open(struct vfio_device *device) > >> return !WARN_ON_ONCE(!READ_ONCE(device->open_count)); > >> } > >> > >> +static bool vfio_kvm_get_kvm_safe(struct kvm *kvm) > >> +{ > >> + bool (*fn)(struct kvm *kvm); > >> + bool ret; > >> + > >> + fn = symbol_get(kvm_get_kvm_safe); > >> + if (WARN_ON(!fn)) In a related vein to Alex's comments about error handling, this should not WARN. WARNing during vfio_kvm_put_kvm() makes sense, but the "get" is somewhat blind. > >> + return false; > >> + > >> + ret = fn(kvm); > >> + > >> + symbol_put(kvm_get_kvm_safe); > >> + > >> + return ret; > >> +} > >> + > >> +static void vfio_kvm_put_kvm(struct kvm *kvm) > >> +{ > >> + void (*fn)(struct kvm *kvm); > >> + > >> + fn = symbol_get(kvm_put_kvm); > >> + if (WARN_ON(!fn)) > >> + return; > >> + > >> + fn(kvm); > >> + > >> + symbol_put(kvm_put_kvm); > >> +}