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 smtp2.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 21EBFC4332F for ; Mon, 7 Feb 2022 23:03:56 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id BD6A240253; Mon, 7 Feb 2022 23:03:55 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id FylHvHJhwTJH; Mon, 7 Feb 2022 23:03:54 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp2.osuosl.org (Postfix) with ESMTPS id 2F4064052E; Mon, 7 Feb 2022 23:03:54 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 2038DC007E; Mon, 7 Feb 2022 23:03:53 +0000 (UTC) Received: from smtp2.osuosl.org (smtp2.osuosl.org [140.211.166.133]) by lists.linuxfoundation.org (Postfix) with ESMTP id E1F29C000B for ; Mon, 7 Feb 2022 23:03:51 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id B6B5F404CD for ; Mon, 7 Feb 2022 23:03:51 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Lw1raJZIbQjK for ; Mon, 7 Feb 2022 23:03:51 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by smtp2.osuosl.org (Postfix) with ESMTPS id D8985400D3 for ; Mon, 7 Feb 2022 23:03:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1644275030; x=1675811030; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=pSiI5bRDWKZ8wcmfvSwFj0dyl6gbbkbtffSYluVkHLo=; b=Dflciez+66v4ikdYlHaEbBwutdllHoEhfINiVoUkCZBiMcgHVR8zPBdA Jv/JvCJwrx42U9Fv1+FsqRs4wzUVmUYGnLXhM0VRThmtVrVSuyc+HLL2I rrfSZTsdnNuXh5SF8fJIAwpZncnwOBAeZOVNHZbjeDf4XSjZzhyyKpxYP a4HAZWEPESrbsw7KVaj8tm6fGoYRXFOXYScbHZpnYkMRLziiy8Xbr7Plf nNxs6S1WqqwjKQXViiKufp0QxUW9S3ySs/3p7cWBb3YYh5OMw0WSdtQ1R S6D4vqq1k+rDH9SiGL8hdXHJYazD9NwCs4hE+MK1+bCNkTiF5Avz5QTef g==; X-IronPort-AV: E=McAfee;i="6200,9189,10251"; a="248774764" X-IronPort-AV: E=Sophos;i="5.88,351,1635231600"; d="scan'208";a="248774764" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Feb 2022 15:03:05 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.88,351,1635231600"; d="scan'208";a="540324061" Received: from otcwcpicx3.sc.intel.com ([172.25.55.73]) by orsmga008.jf.intel.com with ESMTP; 07 Feb 2022 15:03:04 -0800 From: Fenghua Yu To: "Thomas Gleixner" , "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" Subject: [PATCH v4 06/11] x86/fpu: Clear PASID when copying fpstate Date: Mon, 7 Feb 2022 15:02:49 -0800 Message-Id: <20220207230254.3342514-7-fenghua.yu@intel.com> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220207230254.3342514-1-fenghua.yu@intel.com> References: <20220207230254.3342514-1-fenghua.yu@intel.com> MIME-Version: 1.0 Cc: Fenghua Yu , iommu@lists.linux-foundation.org, x86 , linux-kernel X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" The kernel must allocate a Process Address Space ID (PASID) on behalf of each process which will use ENQCMD and program it into the new MSR to communicate the process identity to platform hardware. ENQCMD uses the PASID stored in this MSR to tag requests from this process. The PASID state must be cleared on fork() since fork creates a new address space. For clone(), it would be functionally OK to copy the PASID. However, clearing it is _also_ functionally OK since any PASID use will trigger the #GP handler to populate the MSR. Copying the PASID state has two main downsides: * It requires differentiating fork() and clone() in the code, both in the FPU code and keeping tsk->pasid_activated consistent. * It guarantees that the PASID is out of its init state, which incurs small but non-zero cost on every XSAVE/XRSTOR. The main downside of clearing the PASID at fpstate copy is the future, one-time #GP for the thread. Use the simplest approach: clear the PASID state both on clone() and fork(). Rely on the #GP handler for MSR population in children. Also, just clear the PASID bit from xfeatures if XSAVE is supported. This will have no effect on systems that do not have PASID support. It is virtually zero overhead because 'dst_fpu' was just written and the whole thing is cache hot. Signed-off-by: Fenghua Yu Reviewed-by: Tony Luck Reviewed-by: Thomas Gleixner --- v4: - Add "Reviewed-by: Thomas Gleixner " (Thomas). v2: - Rewrite changelog (Dave Hansen). - Move xfeature tweaking into fpu_clone() and make it unconditional if XSAVE is supported (Dave Hansen). arch/x86/kernel/fpu/core.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 8dea01ffc5c1..19821f027cb3 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -612,6 +612,13 @@ int fpu_clone(struct task_struct *dst, unsigned long clone_flags) fpu_inherit_perms(dst_fpu); fpregs_unlock(); + /* + * Children never inherit PASID state. + * Force it to have its init value: + */ + if (use_xsave()) + dst_fpu->fpstate->regs.xsave.header.xfeatures &= ~XFEATURE_MASK_PASID; + trace_x86_fpu_copy_src(src_fpu); trace_x86_fpu_copy_dst(dst_fpu); -- 2.35.1 _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu