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 8A347C432C1 for ; Tue, 24 Sep 2019 21:03:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 632C921655 for ; Tue, 24 Sep 2019 21:03:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2633480AbfIXVDi (ORCPT ); Tue, 24 Sep 2019 17:03:38 -0400 Received: from mga02.intel.com ([134.134.136.20]:31891 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2633461AbfIXVDi (ORCPT ); Tue, 24 Sep 2019 17:03:38 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 24 Sep 2019 14:03:37 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,545,1559545200"; d="scan'208";a="179612707" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.41]) by orsmga007.jf.intel.com with ESMTP; 24 Sep 2019 14:03:37 -0700 Date: Tue, 24 Sep 2019 14:03:37 -0700 From: Sean Christopherson To: Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, Josh Poimboeuf , Peter Zijlstra Cc: "H. Peter Anvin" , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 0/5] KVM: VMX: Optimize VMX instrs error/fault handling Message-ID: <20190924210337.GE16218@linux.intel.com> References: <20190719204110.18306-1-sean.j.christopherson@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190719204110.18306-1-sean.j.christopherson@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 Paolo, Any chance this can be picked up for 5.4? Josh's kvm_spurious_fault() changes went into 5.3, so this can be taken through the KVM tree, which probably makes the most sense since the non-KVM change is a one line deletion. On Fri, Jul 19, 2019 at 01:41:05PM -0700, Sean Christopherson wrote: > A recent commit reworked __kvm_handle_fault_on_reboot() to play nice with > objtool. An unfortunate side effect is that JMP is now inserted after > most VMX instructions so that the reboot macro can use an actual CALL to > kvm_spurious_fault() instead of a funky PUSH+JMP facsimile in .fixup. > > Rework the low level VMX instruction helpers to handle unexpected faults > manually instead of relying on the "fault on reboot" macro. By using > asm-goto, most helpers can branch directly to an in-function call to > kvm_spurious_fault(), which can then be optimized by compilers to reside > out-of-line at the end of the function instead of inline as done by > "fault on reboot". > > The net impact relative to the current code base is more or less a nop > when building with a compiler that supports __GCC_ASM_FLAG_OUTPUTS__. > A bunch of code that was previously in .fixup gets moved into the slow > paths of functions, but the fast paths are more basically unchanged. > > Without __GCC_ASM_FLAG_OUTPUTS__, manually coding the Jcc is a net > positive as CC_SET() without compiler support almost always generates a > SETcc+CMP+Jcc sequence, which is now replaced with a single Jcc. > > A small bonus is that the Jcc instrs are hinted to predict that the VMX > instr will be successful. > > v2: > - Rebased to x86/master, commit eceffd88ca20 ("Merge branch 'x86/urgent'") > - Reworded changelogs to reference the commit instead lkml link for > the recent changes to __kvm_handle_fault_on_reboot(). > - Added Paolo's acks for patch 1-4 > - Added patch 5 to do more cleanup, which was made possible by rebasing > on top of the __kvm_handle_fault_on_reboot() changes. > > Sean Christopherson (5): > objtool: KVM: x86: Check kvm_rebooting in kvm_spurious_fault() > KVM: VMX: Optimize VMX instruction error and fault handling > KVM: VMX: Add error handling to VMREAD helper > KVM: x86: Drop ____kvm_handle_fault_on_reboot() > KVM: x86: Don't check kvm_rebooting in __kvm_handle_fault_on_reboot() > > arch/x86/include/asm/kvm_host.h | 16 ++---- > arch/x86/kvm/vmx/ops.h | 93 ++++++++++++++++++++------------- > arch/x86/kvm/vmx/vmx.c | 42 +++++++++++++++ > arch/x86/kvm/x86.c | 3 +- > tools/objtool/check.c | 1 - > 5 files changed, 104 insertions(+), 51 deletions(-) > > -- > 2.22.0 >