From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754931AbdK2OLR (ORCPT ); Wed, 29 Nov 2017 09:11:17 -0500 Received: from mx2.suse.de ([195.135.220.15]:34226 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754071AbdK2OLP (ORCPT ); Wed, 29 Nov 2017 09:11:15 -0500 Subject: Re: [RFC PATCH] KVM: x86: Allow Qemu/KVM to use PVH entry point To: Boris Ostrovsky , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= Cc: Maran Wilson , tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, rkrcmar@redhat.com, JBeulich@suse.com, andrew.cooper3@citrix.com, pbonzini@redhat.com, kvm@vger.kernel.org References: <1511897682-32060-1-git-send-email-maran.wilson@oracle.com> <176188ca-51f9-ef12-6e93-46ab2d8b8cfc@suse.com> <20171129085044.kc3yqqdcw3zmp2k2@MacBook-Pro-de-Roger.local> <4d213199-ea65-4410-5b7a-63038215e380@oracle.com> From: Juergen Gross Message-ID: <0162f2cd-2d9e-1c89-bb8e-7ac0089f0b3a@suse.com> Date: Wed, 29 Nov 2017 15:11:12 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <4d213199-ea65-4410-5b7a-63038215e380@oracle.com> Content-Type: text/plain; charset=windows-1252 Content-Language: de-DE Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 29/11/17 15:03, Boris Ostrovsky wrote: > On 11/29/2017 03:50 AM, Roger Pau Monné wrote: >> On Wed, Nov 29, 2017 at 09:21:59AM +0100, Juergen Gross wrote: >>> On 28/11/17 20:34, Maran Wilson wrote: >>>> For certain applications it is desirable to rapidly boot a KVM virtual >>>> machine. In cases where legacy hardware and software support within the >>>> guest is not needed, Qemu should be able to boot directly into the >>>> uncompressed Linux kernel binary without the need to run firmware. >>>> >>>> There already exists an ABI to allow this for Xen PVH guests and the ABI is >>>> supported by Linux and FreeBSD: >>>> >>>> https://xenbits.xen.org/docs/unstable/misc/hvmlite.html >> I would also add a link to: >> >> http://xenbits.xen.org/docs/unstable/hypercall/x86_64/include,public,arch-x86,hvm,start_info.h.html#Struct_hvm_start_info >> >>>> This PoC patch enables Qemu to use that same entry point for booting KVM >>>> guests. >>>> >>>> Even though the code is still PoC quality, I'm sending this as an RFC now >>>> since there are a number of different ways the specific implementation >>>> details can be handled. I chose a shared code path for Xen and KVM guests >>>> but could just as easily create a separate code path that is advertised by >>>> a different ELF note for KVM. There also seems to be some flexibility in >>>> how the e820 table data is passed and how (or if) it should be identified >>>> as e820 data. As a starting point, I've chosen the options that seem to >>>> result in the smallest patch with minimal to no changes required of the >>>> x86/HVM direct boot ABI. >>> I like the idea. >>> >>> I'd rather split up the different hypervisor types early and use a >>> common set of service functions instead of special casing xen_guest >>> everywhere. This would make it much easier to support the KVM PVH >>> boot without the need to configure the kernel with CONFIG_XEN. >>> >>> Another option would be to use the same boot path as with grub: set >>> the boot params in zeropage and start at startup_32. >> I think I prefer this approach since AFAICT it should allow for >> greater code share with the common boot path. > > zeropage is x86/Linux-specific so we'd need some sort of firmware (like > grub) between a hypervisor and Linux to convert hvm_start_info to > bootparams. qemu? Juergen