From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751583AbcGMJfe (ORCPT ); Wed, 13 Jul 2016 05:35:34 -0400 Received: from mail-lf0-f67.google.com ([209.85.215.67]:34108 "EHLO mail-lf0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751211AbcGMJfa (ORCPT ); Wed, 13 Jul 2016 05:35:30 -0400 Subject: Re: [RFC PATCH 4/4] KVM: vmx: add support for emulating UMIP To: Yang Zhang , linux-kernel@vger.kernel.org, kvm@vger.kernel.org References: <1468351223-3250-1-git-send-email-pbonzini@redhat.com> <1468351223-3250-5-git-send-email-pbonzini@redhat.com> <8f893604-1e80-2979-bc87-45a049238e58@gmail.com> From: Paolo Bonzini Message-ID: Date: Wed, 13 Jul 2016 11:35:10 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1 MIME-Version: 1.0 In-Reply-To: <8f893604-1e80-2979-bc87-45a049238e58@gmail.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 13/07/2016 11:21, Yang Zhang wrote: >> >> + if ((cr4 & X86_CR4_UMIP) && !boot_cpu_has(X86_FEATURE_UMIP)) { >> + vmcs_set_bits(SECONDARY_VM_EXEC_CONTROL, >> + SECONDARY_EXEC_DESC); >> + hw_cr4 &= ~X86_CR4_UMIP; >> + } else >> + vmcs_clear_bits(SECONDARY_VM_EXEC_CONTROL, >> + SECONDARY_EXEC_DESC); >> + > > Since the faults based on privilege level have priority over VM exits. > So we don't need to enable/disable SECONDARY_EXEC_DESC dynamically. > Instead, we can set it unconditionally. I'm setting it dynamically because it slows down LGDT, LLDT, LIDT and LTR. Paolo