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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 DD5FECA9EA0 for ; Tue, 22 Oct 2019 06:16:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BEA7C21920 for ; Tue, 22 Oct 2019 06:16:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387688AbfJVGQb (ORCPT ); Tue, 22 Oct 2019 02:16:31 -0400 Received: from mga07.intel.com ([134.134.136.100]:49039 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387508AbfJVGQb (ORCPT ); Tue, 22 Oct 2019 02:16:31 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Oct 2019 23:16:30 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.67,326,1566889200"; d="scan'208";a="227583987" Received: from local-michael-cet-test.sh.intel.com (HELO localhost) ([10.239.159.128]) by fmsmga002.fm.intel.com with ESMTP; 21 Oct 2019 23:16:21 -0700 Date: Tue, 22 Oct 2019 14:19:15 +0800 From: Yang Weijiang To: Jim Mattson Cc: Yang Weijiang , kvm list , LKML , Paolo Bonzini , Sean Christopherson , "Michael S. Tsirkin" , Radim =?utf-8?B?S3LEjW3DocWZ?= , yu.c.zhang@intel.com, alazar@bitdefender.com Subject: Re: [PATCH v5 0/9] Enable Sub-page Write Protection Support Message-ID: <20191022061915.GA18889@local-michael-cet-test> References: <20190917085304.16987-1-weijiang.yang@intel.com> <20191011075033.GA11817@local-michael-cet-test> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.3 (2019-02-01) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, Oct 11, 2019 at 09:11:54AM -0700, Jim Mattson wrote: > On Fri, Oct 11, 2019 at 12:48 AM Yang Weijiang wrote: > > > > On Thu, Oct 10, 2019 at 02:42:51PM -0700, Jim Mattson wrote: > > > On Tue, Sep 17, 2019 at 1:52 AM Yang Weijiang wrote: > > > > > > > > EPT-Based Sub-Page write Protection(SPP)is a HW capability which allows > > > > Virtual Machine Monitor(VMM) to specify write-permission for guest > > > > physical memory at a sub-page(128 byte) granularity. When this > > > > capability is enabled, the CPU enforces write-access check for sub-pages > > > > within a 4KB page. > > > > > > > > The feature is targeted to provide fine-grained memory protection for > > > > usages such as device virtualization, memory check-point and VM > > > > introspection etc. > > > > > > > > SPP is active when the "sub-page write protection" (bit 23) is 1 in > > > > Secondary VM-Execution Controls. The feature is backed with a Sub-Page > > > > Permission Table(SPPT), SPPT is referenced via a 64-bit control field > > > > called Sub-Page Permission Table Pointer (SPPTP) which contains a > > > > 4K-aligned physical address. > > > > > > > > To enable SPP for certain physical page, the gfn should be first mapped > > > > to a 4KB entry, then set bit 61 of the corresponding EPT leaf entry. > > > > While HW walks EPT, if bit 61 is set, it traverses SPPT with the guset > > > > physical address to find out the sub-page permissions at the leaf entry. > > > > If the corresponding bit is set, write to sub-page is permitted, > > > > otherwise, SPP induced EPT violation is generated. > > > > > > How do you handle sub-page permissions for instructions emulated by kvm? > > How about checking if the gpa is SPP protected, if it is, inject some > > exception to guest? > The SPP semantics are well-defined. If a kvm-emulated instruction > tries to write to a sub-page that is write-protected, then an > SPP-induced EPT violation should be synthesized. Hi, Jim, Regarding the emulated instructions in KVM, there're quite a few instructions can write guest memory, such as MOVS, XCHG, INS etc., check each destination against SPP protected area would be trivial if deals with them individually, and PIO/MMIO induced vmexit/page_fault also can link to a SPP protected page, e.g., a string instruction's the destination is SPP protected memory. Is there a good way to intercept these writes? emulate_ops.write_emulated() is called in most of the emulation cases to check and write guest memory, but not sure it's suitable. Do you have any suggestion? Thanks!