Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752279AbdLKSId (ORCPT ); Mon, 11 Dec 2017 13:08:33 -0500 Received: from mail-it0-f68.google.com ([209.85.214.68]:37483 "EHLO mail-it0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751268AbdLKSIb (ORCPT ); Mon, 11 Dec 2017 13:08:31 -0500 X-Google-Smtp-Source: ACJfBosvziXmyUnlDy4nFtfpcPHhsIW0REnLAZ1SlrbG0ugRd+p1wyoOk+U+yQ3FZ4KCP9snURUL8xYPhW5BdHRL820= MIME-Version: 1.0 In-Reply-To: <4dfe07e2-e70d-0074-af17-9d27e73cc115@gmail.com> References: <1512728546-4365-1-git-send-email-quan.xu0@gmail.com> <4dfe07e2-e70d-0074-af17-9d27e73cc115@gmail.com> From: Jim Mattson Date: Mon, 11 Dec 2017 10:08:29 -0800 Message-ID: Subject: Re: [PATCH] KVM: VMX: drop I/O permission bitmaps To: Quan Xu Cc: kvm list , LKML , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Paolo Bonzini , David Hildenbrand Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by nfs id vBBI8dru012882 Content-Length: 1981 Lines: 58 Removing these two lines from the initialization of field_to_offset_table[] means that vmcs_field_to_offset() will return -ENOENT for IO_BITMAP_A or IO_BITMAP_B. Hence, handle_vmread and handle_vmwrite will incorrectly report these fields as unsupported VMCS components if an L1 hypervisor tries to access them. On Sun, Dec 10, 2017 at 9:37 PM, Quan Xu wrote: > > > On 2017/12/09 01:31, Jim Mattson wrote: >> >> On Fri, Dec 8, 2017 at 2:22 AM, Quan Xu wrote: >>> >>> From: Quan Xu >>> >>> Since KVM removes the only I/O port 0x80 bypass on Intel hosts, >>> clear CPU_BASED_USE_IO_BITMAPS and set CPU_BASED_UNCOND_IO_EXITING >>> bit. Then these I/O permission bitmaps are not used at all, so >>> drop I/O permission bitmaps. >>> >>> Signed-off-by: Jim Mattson >>> Signed-off-by: Radim Krčmář >>> Signed-off-by: Quan Xu >>> --- >>> arch/x86/kvm/vmx.c | 17 +---------------- >>> 1 files changed, 1 insertions(+), 16 deletions(-) >>> >>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c >>> index 2fd9a8c..3e4f760 100644 >>> --- a/arch/x86/kvm/vmx.c >>> +++ b/arch/x86/kvm/vmx.c >>> @@ -771,8 +771,6 @@ enum segment_cache_field { >>> FIELD(HOST_FS_SELECTOR, host_fs_selector), >>> FIELD(HOST_GS_SELECTOR, host_gs_selector), >>> FIELD(HOST_TR_SELECTOR, host_tr_selector), >>> - FIELD64(IO_BITMAP_A, io_bitmap_a), >>> - FIELD64(IO_BITMAP_B, io_bitmap_b), >> >> These two lines should stay. > > Jim, could you explain why these two lines should stay? > > > IIUC, the main concern is from nested virtualization, which still uses > io_bitmap_a/io_bitmap_b.. > if so, we really need to further clean up these code, as > > CPU_BASED_USE_IO_BITMAPS is clear, and CPU_BASED_UNCOND_IO_EXITING is set > for both L0/L2. after new patches which I mentioned > in this thread. > > right? > > Alibaba Cloud > Quan > > >