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 7C1D5C43334 for ; Thu, 6 Sep 2018 14:18:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2F0D12086B for ; Thu, 6 Sep 2018 14:18:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2F0D12086B 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 S1729991AbeIFSyN (ORCPT ); Thu, 6 Sep 2018 14:54:13 -0400 Received: from mga04.intel.com ([192.55.52.120]:25114 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728905AbeIFSyM (ORCPT ); Thu, 6 Sep 2018 14:54:12 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 06 Sep 2018 07:18:27 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.53,338,1531810800"; d="scan'208";a="72112674" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.20]) by orsmga006.jf.intel.com with ESMTP; 06 Sep 2018 07:18:25 -0700 Date: Thu, 6 Sep 2018 07:18:25 -0700 From: Sean Christopherson To: Borislav Petkov Cc: Brijesh Singh , 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: <20180906141825.GB370@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180906135041.GB32336@linux.intel.com> 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 06:50:41AM -0700, Sean Christopherson wrote: > On Thu, Sep 06, 2018 at 02:24:23PM +0200, Borislav Petkov wrote: > > On Thu, Sep 06, 2018 at 06:43:02AM -0500, Brijesh Singh wrote: > > > Currently, the per-cpu pvclock data is allocated dynamically when > > > cpu > HVC_BOOT_ARRAY_SIZE. The physical address of this variable is > > > shared between the guest and the hypervisor hence it must be mapped as > > > unencrypted (ie. C=0) when SEV is active. > > > > > > When SEV is active, we will be wasting fairly sizeable amount of memory > > > since each CPU will be doing a separate 4k allocation so that it can clear > > > C-bit. Let's define few extra static page sized array of pvclock data. > > > In the preparatory stage of CPU hotplug, use the element of this static > > > array to avoid the dynamic allocation. This array will be put in > > > the .data..decrypted section so that its mapped with C=0 during the boot. > > > > > > In non-SEV case, this static page will unused and free'd by the > > > free_decrypted_mem(). > > > > > > diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h > > > index 802b2eb..aa204af 100644 > > > --- a/arch/x86/include/asm/mem_encrypt.h > > > +++ b/arch/x86/include/asm/mem_encrypt.h > > > @@ -48,11 +48,13 @@ int __init early_set_memory_encrypted(unsigned long vaddr, unsigned long size); > > > > > > /* Architecture __weak replacement functions */ > > > void __init mem_encrypt_init(void); > > > +void __init free_decrypted_mem(void); > > > > > > bool sme_active(void); > > > bool sev_active(void); > > > > > > #define __decrypted __attribute__((__section__(".data..decrypted"))) > > > +#define __decrypted_hvclock __attribute__((__section__(".data..decrypted_hvclock"))) > > > > 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().