From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932578AbbJMQpH (ORCPT ); Tue, 13 Oct 2015 12:45:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53044 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932358AbbJMQpE (ORCPT ); Tue, 13 Oct 2015 12:45:04 -0400 Date: Tue, 13 Oct 2015 18:45:01 +0200 From: Radim =?utf-8?B?S3LEjW3DocWZ?= To: Paolo Bonzini Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, aderumier@odiso.com, stable@vger.kernel.org Subject: Re: [PATCH 2/2] KVM: x86: map/unmap private slots in __x86_set_memory_region Message-ID: <20151013164500.GC6877@potion.brq.redhat.com> References: <1444651758-6926-1-git-send-email-pbonzini@redhat.com> <1444651758-6926-3-git-send-email-pbonzini@redhat.com> <20151013153957.GA9987@potion.brq.redhat.com> <561D3126.8060402@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <561D3126.8060402@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2015-10-13 18:28+0200, Paolo Bonzini: > On 13/10/2015 17:39, Radim Krčmář wrote: >> 2015-10-12 14:09+0200, Paolo Bonzini: >>> Otherwise, two copies (one of them never used and thus bogus) are >>> allocated for the regular and SMM address spaces. This breaks >>> SMM with EPT but without unrestricted guest support, because the >>> SMM copy of the identity page map is all zeros. >> >> (Have you found out why EPT+unrestricted didn't use the alternative SMM >> mapping as well?) > > Yes, that I already knew; EPT+unrestricted uses CR0.PG=0 directly so > it doesn't use the identity page at all. (CR0.PG=0 w/o unrestricted > instead runs with CR0.PG=1. CR3 load and store exits are enabled, > and the guest CR3 always points to the identity page map while the > guest runs). Thank you. >>> + } else { >>> + if (!slot->npages) >>> + return 0; >>> + >>> + hva = 0; >>> + } >>> + >>> + old = *slot; >> >> (Assignment could be in the 'else' == !size branch, GCC would have fun.) > > It would have fun _and_ warn, which is why it's not in the else branch. :) I wondered if its "used uninitialized" analyzer got any better :)