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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B21F2C433F5 for ; Thu, 6 Sep 2018 19:47:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5F8152075B for ; Thu, 6 Sep 2018 19:47:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5F8152075B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729287AbeIGAYW (ORCPT ); Thu, 6 Sep 2018 20:24:22 -0400 Received: from mga11.intel.com ([192.55.52.93]:47147 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728461AbeIGAYV (ORCPT ); Thu, 6 Sep 2018 20:24:21 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 06 Sep 2018 12:47:20 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.53,339,1531810800"; d="scan'208";a="255116529" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.20]) by orsmga005.jf.intel.com with ESMTP; 06 Sep 2018 12:47:10 -0700 Date: Thu, 6 Sep 2018 12:47:10 -0700 From: Sean Christopherson To: Brijesh Singh Cc: Borislav Petkov , x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Tom Lendacky , Thomas Gleixner , "H. Peter Anvin" , Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= Subject: Re: [PATCH v5 5/5] x86/kvm: Avoid dynamic allocation of pvclock data when SEV is active Message-ID: <20180906194710.GA16605@linux.intel.com> References: <1536234182-2809-1-git-send-email-brijesh.singh@amd.com> <1536234182-2809-6-git-send-email-brijesh.singh@amd.com> <20180906122423.GA11144@zn.tnic> <20180906135041.GB32336@linux.intel.com> <20180906141825.GB370@linux.intel.com> <20180906184750.GB4570@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 06, 2018 at 02:24:32PM -0500, Brijesh Singh wrote: > > > On 09/06/2018 01:47 PM, Sean Christopherson wrote: > >On Thu, Sep 06, 2018 at 01:37:50PM -0500, Brijesh Singh wrote: > >> > >> > >>On 09/06/2018 09:18 AM, Sean Christopherson wrote: > >>.... > >> > >>>>> > >>>>>So are we going to be defining a decrypted section for every piece of > >>>>>machinery now? > >>>>> > >>>>>That's a bit too much in my book. > >>>>> > >>>>>Why can't you simply free everything in .data..decrypted on !SVE guests? > >>>> > >>>>That would prevent adding __decrypted to existing declarations, e.g. > >>>>hv_clock_boot, which would be ugly in its own right. A more generic > >>>>solution would be to add something like __decrypted_exclusive to mark > >>>>data that is used if and only if SEV is active, and then free the > >>>>SEV-only data when SEV is disabled. > >>> > >>>Oh, and we'd need to make sure __decrypted_exclusive is freed when > >>>!CONFIG_AMD_MEM_ENCRYPT, and preferably !sev_active() since the big > >>>array is used only if SEV is active. This patch unconditionally > >>>defines hv_clock_dec but only frees it if CONFIG_AMD_MEM_ENCRYPT=y && > >>>!mem_encrypt_active(). > >>> > >> > >>Again we have to consider the bare metal scenario while doing this. The > >>aux array you proposed will be added in decrypted section only when > >>CONFIG_AMD_MEM_ENCRYPT=y. If CONFIG_AMD_MEM_ENCRYPT=n then nothng > >>gets put in .data.decrypted section. At the runtime, if memory > >>encryption is active then .data.decrypted_hvclock will contains useful > >>data. > >> > >>The __decrypted attribute in "" when CONFIG_AMD_MEM_ENCRYPT=n. > > > >Right, but won't the data get dumped into the regular .bss in that > >case, i.e. needs to be freed? > > > > > Yes, the auxiliary array will dumped into the regular .bss when > CONFIG_AMD_MEM_ENCRYPT=n. Typically it will be few k, I am not > sure if its worth complicating the code to save those extra memory. > Most of the distro's have CONFIG_AMD_MEM_ENCRYPT=y anyways. I just realized that we'll try to create a bogus array if 'NR_CPUS <= HVC_BOOT_ARRAY_SIZE'. A bit ugly, but we could #ifdef away both that and CONFIG_AMD_MEM_ENCRYPT=n in a single shot, e.g.: #if defined(CONFIG_AMD_MEM_ENCRYPT) && NR_CPUS > HVC_BOOT_ARRAY_SIZE #define HVC_AUX_ARRAY_SIZE \ PAGE_ALIGN((NR_CPUS - HVC_BOOT_ARRAY_SIZE) * \ sizeof(struct pvclock_vsyscall_time_info)) static struct pvclock_vsyscall_time_info hv_clock_aux[HVC_AUX_ARRAY_SIZE] __decrypted __aligned(PAGE_SIZE); #endif