From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755392AbdK2Ouj (ORCPT ); Wed, 29 Nov 2017 09:50:39 -0500 Received: from mail-wm0-f68.google.com ([74.125.82.68]:44405 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751172AbdK2Ouh (ORCPT ); Wed, 29 Nov 2017 09:50:37 -0500 X-Google-Smtp-Source: AGs4zMZJGh59+ONQmo35oaQ68bnKH0fqScnieDHwD+NKMbiUmLY68DK0FwyjV6XISUl059pNDCXptw== Subject: Re: [RFC PATCH] KVM: x86: Allow Qemu/KVM to use PVH entry point To: Juergen Gross , 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, 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> <0162f2cd-2d9e-1c89-bb8e-7ac0089f0b3a@suse.com> <20171129141810.q3s3xflsflpjovdd@MacBook-Pro-de-Roger.local> <96f9b4a5-7cb6-19c3-227d-8c48916d5969@oracle.com> <25d6db63-a57d-b15c-2d43-e96c506b4824@redhat.com> From: Paolo Bonzini Message-ID: <1a529a09-2b84-a730-7518-158489303377@redhat.com> Date: Wed, 29 Nov 2017 15:50:27 +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: Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 29/11/2017 15:47, Juergen Gross wrote: > On 29/11/17 15:44, Paolo Bonzini wrote: >> In either case, you would have a new option ROM. It could either be >> very simple and similar to multiboot.S, or it could be larger and do the >> same task as xen-pvh.S and enlighten_pvh.c (then get the address of >> startup_32 or startup_64 from FW_CFG_KERNEL_ENTRY and jump there). The >> ugly part is that the option ROM would have to know more details about >> what it is going to boot, including for example whether it's 32-bit or >> 64-bit, so I don't really think it is a good idea. > > As grub2 doesn't have to know, qemu shouldn't have to know either. That would be exactly what linuxboot-dma.c does already, but it's slower than PVH because Linux has to uncompress itself. The above thought experiment would make QEMU able to boot a PVH kernel without any changes to Linux. Paolo