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 D1453C43217 for ; Fri, 28 Jan 2022 20:29:29 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id 8838340B1F; Fri, 28 Jan 2022 20:29:29 +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 QvYeyhjEfdnu; Fri, 28 Jan 2022 20:29:28 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp2.osuosl.org (Postfix) with ESMTPS id F041D405CF; Fri, 28 Jan 2022 20:29:27 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id B5CFEC001A; Fri, 28 Jan 2022 20:29:27 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [140.211.166.137]) by lists.linuxfoundation.org (Postfix) with ESMTP id 22CF4C001A for ; Fri, 28 Jan 2022 20:29:25 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id 0198940939 for ; Fri, 28 Jan 2022 20:29:25 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Authentication-Results: smtp4.osuosl.org (amavisd-new); dkim=pass (2048-bit key) header.d=intel.com Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id TM5uiaQB0ceo for ; Fri, 28 Jan 2022 20:29:24 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by smtp4.osuosl.org (Postfix) with ESMTPS id 50AAA4022C for ; Fri, 28 Jan 2022 20:29:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1643401764; x=1674937764; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=6OsPHurfIhjKuFzgyw4DA47vvdGN8VlHRe3+l/zPVbY=; b=eOsSiTI7CE5maJbpJd1HcVVExMTnM4rxqGAUdQkAhyPFpoWxqRuvyjnO QIf+65X01pANCzlxEUUhqzTmsfm2DY8ZSWVXz0ZnAGQabJqQo336mRCdz jabrO0KWO58guoYg94EKkWSAcZ1g08k1vkN/NsBrJtgd0oXAKEEzqa2ym wHrgsJDDOJgLxCVNtnLUMgXLmc9yDYTHE16sQZUq7IvZzMDATJzVeCszX mjsYDa03jC2P/pgcGPNjbERyhrg0HQZb9Ychj5OArOFlNmnnj9TbNtRNY nAVmpCz2bEHZp7+HkuBdGiE3a36fV2EewKyaLG+23LyYLeY/CCl99zS1U Q==; X-IronPort-AV: E=McAfee;i="6200,9189,10241"; a="227862443" X-IronPort-AV: E=Sophos;i="5.88,324,1635231600"; d="scan'208";a="227862443" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Jan 2022 12:29:22 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.88,324,1635231600"; d="scan'208";a="618827703" Received: from otcwcpicx3.sc.intel.com ([172.25.55.73]) by FMSMGA003.fm.intel.com with ESMTP; 28 Jan 2022 12:29:22 -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 v3 06/11] x86/fpu: Clear PASID when copying fpstate Date: Fri, 28 Jan 2022 12:29:00 -0800 Message-Id: <20220128202905.2274672-7-fenghua.yu@intel.com> X-Mailer: git-send-email 2.35.0 In-Reply-To: <20220128202905.2274672-1-fenghua.yu@intel.com> References: <20220128202905.2274672-1-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 --- 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); -- 2.35.0 _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu