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 C1D45C433F5 for ; Fri, 4 Feb 2022 23:22:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378067AbiBDXWP (ORCPT ); Fri, 4 Feb 2022 18:22:15 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:35074 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235330AbiBDXWO (ORCPT ); Fri, 4 Feb 2022 18:22:14 -0500 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1644016932; 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=DBK2yZNYxvLy8x/PDAEC/NG09v5eFxGT61LctE0oxSY=; b=aBDit1LkinvPfla5El5YaYm0kJu7cY2oxGsuMNIho93oSkb23VHPKLKfDIuNZT5GL2ZXsK TMF2V7N8gzmmi0wwtlMRKOtVPURyNjzeSE4j1kVjooS6o1HavQyxx7MlHx8vnTkHQtG7/x Faijrr64fpfWl3bPcBV63Zh5FNahx4KE7LxngzjUc2UixffxT5Ba0OuhgmulGbv8SbFNO7 sd06yCQaFBq0jrREyL0RfZDMXkfzYpSTa+w+DKPGvNXH3JOkQB4gXct2S8dy9ubTJs1Ypt 0fNlno6ElIe3scEa9P6ceksKYw3OHjRhSlE2E8tuaK0w0orsacxqjRRdw4JxDg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1644016932; 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=DBK2yZNYxvLy8x/PDAEC/NG09v5eFxGT61LctE0oxSY=; b=0USIK3EJKSRVIDVzeQ8qFn4rlRy37TsVmeexs71EbJ4kLHSFBJnN3VeIjAdrtxVUaJU3HP dqhQiGyXYf0dqEDA== To: Fenghua Yu , Dave Hansen , Ingo Molnar , Borislav Petkov , Peter Zijlstra , Andy Lutomirski , Tony Luck , Lu Baolu , Joerg Roedel , Josh Poimboeuf , Jacob Pan , Ashok Raj , Ravi V Shankar Cc: iommu@lists.linux-foundation.org, x86 , linux-kernel , Fenghua Yu Subject: Re: [PATCH v3 04/11] kernel/fork: Initialize mm's PASID In-Reply-To: <20220128202905.2274672-5-fenghua.yu@intel.com> References: <20220128202905.2274672-1-fenghua.yu@intel.com> <20220128202905.2274672-5-fenghua.yu@intel.com> Date: Sat, 05 Feb 2022 00:22:12 +0100 Message-ID: <87wniab4kb.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 28 2022 at 12:28, Fenghua Yu wrote: > A new mm doesn't have a PASID yet when it's created. Initialize > the mm's PASID on fork() or for init_mm to INVALID_IOASID (-1). I must be missing something here. > diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h > index aa5f09ca5bcf..c74d1edbac2f 100644 > --- a/include/linux/sched/mm.h > +++ b/include/linux/sched/mm.h > @@ -8,6 +8,7 @@ > #include > #include > #include > +#include > > /* > * Routines for handling mm_structs > @@ -433,4 +434,13 @@ static inline void membarrier_update_current_mm(struct mm_struct *next_mm) > } > #endif > > +#ifdef CONFIG_IOMMU_SVA > +static inline void mm_pasid_init(struct mm_struct *mm) > +{ > + mm->pasid = INVALID_IOASID; > +} > +#else > +static inline void mm_pasid_init(struct mm_struct *mm) {} > +#endif > + > #endif /* _LINUX_SCHED_MM_H */ So this adds mm_pasid_init() to linux/sched/mm.h which replaces: > -static void mm_init_pasid(struct mm_struct *mm) > -{ > -#ifdef CONFIG_IOMMU_SVA > - mm->pasid = INIT_PASID; > -#endif > -} > - I.e. already existing code which is initializing mm->pasid with INIT_PASID (0) while the replacement initializes it with INVALID_IOASID (-1). The change log does not have any information about why INIT_PASID is the wrong initialization value and why this change is not having any side effects. It neither mentions why having this in a global available header makes sense when the only call site is in the C file from which the already existing function is removed. Thanks, tglx