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,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 7F339C3F2CD for ; Mon, 2 Mar 2020 19:19:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5F4E520842 for ; Mon, 2 Mar 2020 19:19:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727524AbgCBTTm (ORCPT ); Mon, 2 Mar 2020 14:19:42 -0500 Received: from mga17.intel.com ([192.55.52.151]:18572 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727126AbgCBTTl (ORCPT ); Mon, 2 Mar 2020 14:19:41 -0500 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 fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 02 Mar 2020 11:19:41 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,508,1574150400"; d="scan'208";a="412415599" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.202]) by orsmga005.jf.intel.com with ESMTP; 02 Mar 2020 11:19:41 -0800 Date: Mon, 2 Mar 2020 11:19:41 -0800 From: Sean Christopherson To: Paolo Bonzini Cc: Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 10/13] KVM: x86: Shrink the usercopy region of the emulation context Message-ID: <20200302191940.GD6244@linux.intel.com> References: <20200218232953.5724-1-sean.j.christopherson@intel.com> <20200218232953.5724-11-sean.j.christopherson@intel.com> <87r1yhi6ex.fsf@vitty.brq.redhat.com> <727b8d16-2bab-6621-1f20-dc024ee65f10@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <727b8d16-2bab-6621-1f20-dc024ee65f10@redhat.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 Mon, Mar 02, 2020 at 07:40:27PM +0100, Paolo Bonzini wrote: > On 26/02/20 18:51, Vitaly Kuznetsov wrote: > >> + > >> + /* Here begins the usercopy section. */ > >> + struct operand src; > >> + struct operand src2; > >> + struct operand dst; > > Out of pure curiosity, how certain are we that this is going to be > > enough for userspaces? > > > > And also, where exactly are the user copies done? Anything that funnels into ctxt->ops->read_std() or ctxt->ops->write_std(), e.g. if (ctxt->src2.type == OP_MEM) { rc = segmented_read(ctxt, ctxt->src2.addr.mem, &ctxt->src2.val, ctxt->src2.bytes); if (rc != X86EMUL_CONTINUE) goto done; } segmented_read() : @data = &ctxt->src2.val | |-> read_emulated() | |-> ctxt->ops->read_emulated() / emulator_read_emulated() | |-> emulator_read_write() | |-> emulator_read_write_onepage() | |-> ops->read_write_emulate() / read_emulate() | |-> kvm_vcpu_read_guest() | ... |-> __kvm_read_guest_page() | |-> __copy_from_user(data, ...)