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 EA999C433EF for ; Fri, 20 May 2022 14:49:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350473AbiETOt2 (ORCPT ); Fri, 20 May 2022 10:49:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50640 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350441AbiETOtZ (ORCPT ); Fri, 20 May 2022 10:49:25 -0400 Received: from mail-pj1-x1031.google.com (mail-pj1-x1031.google.com [IPv6:2607:f8b0:4864:20::1031]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 741031737E8 for ; Fri, 20 May 2022 07:49:24 -0700 (PDT) Received: by mail-pj1-x1031.google.com with SMTP id z7-20020a17090abd8700b001df78c7c209so11706325pjr.1 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=V2PfQer33AMY+tKa5+c2UZXBJzzIY9PLF2Oh63FejPq41+Fa7YnPtrgobmXgu3JIIK zempQmOPY3pVvYKAqXPPwuPV1pYxYfllFNkH7eCRV7+HGA2aAK7EcydBHt0EWUKAsBqG pnCVGziXy6KC17rnZ91st9fixuA3qjXYQGt9xb9uRhUMls9kOir3rNcuEvr1ErA5V41o WTBbyYxfRRlN5WY+NDgULNeps3hNTXEaxhfyOal5G6bNgxz6q+tsrj9pib8WNonhsAuc /ESxHQ4RVn2jvCYIfwEg8ce5X4L9460rOtvvDUzdFoufm7z9DMQZeedIvMFSseNh3+XO SuKw== X-Gm-Message-State: AOAM530fW1GzA5xCacRvblqhHCVv/2VKAMtVBFn9Ata0oD4Vzu93+kfG eo17q+kNKyN9eVkGDzKVN3jUlg== 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: linux-kernel@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.