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 B1A4AC433F5 for ; Fri, 20 May 2022 14:49:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350461AbiETOt0 (ORCPT ); Fri, 20 May 2022 10:49:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50632 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350409AbiETOtZ (ORCPT ); Fri, 20 May 2022 10:49:25 -0400 Received: from mail-pj1-x1030.google.com (mail-pj1-x1030.google.com [IPv6:2607:f8b0:4864:20::1030]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 726331737DE for ; Fri, 20 May 2022 07:49:24 -0700 (PDT) Received: by mail-pj1-x1030.google.com with SMTP id t11-20020a17090a6a0b00b001df6f318a8bso11681795pjj.4 for ; Fri, 20 May 2022 07:49:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=f1NRmKh5Rhsxk9PmTkCXw/A8MNF/NhHvXEmLtT1IpHE=; b=QZq4zlFkytnpkoKLHXfPVTDwcf9UtqLUzauaG+cSAnYVATmyPX81nLvs7hhmFyWBhe CbWOigB+fYckwMOkgfGsCJ0urV15tiqwqIWj3aFa+InB8MHitijRYDLZqlyktUnOHdzK 1E/BkiyELKk1vHvrUiViJjXSEKszJYX395HLQWuDEFyfTdtW8F8lUTlYL3NXfdkIM609 87aKY/zH8Ngh+Qhb2+aojh/ynF4pK/Flk9qjGL93ex6Hec84NYU6elLaxICYnxjkr8Kp hFXOe3z4bKd/JlXrfT/tb54mcnS+iQd+zJ/dt7EZNoN1Gcp2G5wD2CmWphQ7IJj+qdGI PXcQ== 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=f1NRmKh5Rhsxk9PmTkCXw/A8MNF/NhHvXEmLtT1IpHE=; b=c9ydaG4d0bisZqfZAPAmzTebcdFLnjwjNp4CCcLPWpTO4qyfQJbBZ5Y/VYS+QPWuYn d0BzYIMLUSTGAuJ/c75Q8Bn+muVpYRc3GMA7P8V2ptpw4XIUk8I03Fl4CewVmmGDuZ4U hp6cBmrxmVLbhfn+uV74UOPvYRmNgiPEJ9ysJ8p0qW3MssZdcBMgdcfHKUJQT/wAEEn+ 9CNt1VyOVfdLUURkGmCVeFcm1Ktkdw6GEn0373KBlY20BiyTLkOvAr7wvSj96elML43v Wmgbb60fQgWsXWwHtKFsR5zGvfqvN2ZhIqwffzjuI4tAlPXVMThSoJm5yYebzAnIUuls LQEA== X-Gm-Message-State: AOAM5320CO6seeR19EWNiSGTh/dvFW7g3ub+oTKRAfL1lYSfNYVmX+I6 GnQLRthGd+wS1l1dlqyTLDY7RQ== X-Google-Smtp-Source: ABdhPJyEbl4XhIo7xvkFoiHhRz1H+L7M1KeQghT2ol/Uc3pk9wA/MY8rSpYGOfK4Zij5dnpx8N4gnA== X-Received: by 2002:a17:902:d502:b0:161:bc5f:7b2d with SMTP id b2-20020a170902d50200b00161bc5f7b2dmr9675245plg.140.1653058163758; Fri, 20 May 2022 07:49:23 -0700 (PDT) Received: from google.com (157.214.185.35.bc.googleusercontent.com. [35.185.214.157]) by smtp.gmail.com with ESMTPSA id t4-20020a170902e84400b0015e8d4eb248sm5871611plg.146.2022.05.20.07.49.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 20 May 2022 07:49:23 -0700 (PDT) Date: Fri, 20 May 2022 14:49:19 +0000 From: Sean Christopherson To: Paolo Bonzini Cc: Yajun Deng , vkuznets@redhat.com, wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] KVM: x86: Move kzalloc out of atomic context on PREEMPT_RT Message-ID: References: <20220519090218.2230653-1-yajun.deng@linux.dev> 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 Fri, May 20, 2022, Paolo Bonzini wrote: > On 5/19/22 17:11, Sean Christopherson wrote: > > AFAICT, kfree() is safe to call under a raw spinlock, so this? Compile tested > > only... > > Freeing outside the lock is not complicated enough to check if it is: > > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c > index 6aa1241a80b7..f849f7c9fbf2 100644 > --- a/arch/x86/kernel/kvm.c > +++ b/arch/x86/kernel/kvm.c > @@ -229,12 +229,15 @@ void kvm_async_pf_task_wake(u32 token) > dummy->cpu = smp_processor_id(); > init_swait_queue_head(&dummy->wq); > hlist_add_head(&dummy->link, &b->list); > + dummy = NULL; > } else { > - kfree(dummy); > apf_task_wake_one(n); > } > raw_spin_unlock(&b->lock); > - return; > + > + /* A dummy token might be allocated and ultimately not used. */ > + if (dummy) > + kfree(dummy); > } > EXPORT_SYMBOL_GPL(kvm_async_pf_task_wake); > > > I queued your patch with the above fixup. Ha, I wrote it exactly that way, then grepped around found a few instances of kfree() being called in side a raw spinlock, so changed it back :-) 100% agree it's not worth having to generate another patch if it turns out those callers are wrong.