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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 6104FC433DF for ; Tue, 26 May 2020 12:50:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 322AE20787 for ; Tue, 26 May 2020 12:50:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="TFaO+/3V" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729303AbgEZMuf (ORCPT ); Tue, 26 May 2020 08:50:35 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:39213 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728558AbgEZMuf (ORCPT ); Tue, 26 May 2020 08:50:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1590497433; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=MJSM3PD7cXbri59EHpWEca36HJ8EesRGj50MuybBvxc=; b=TFaO+/3Vu3SKfbYNBG6sNzw83S/luUq9uqmjqaa5Uo9gQrWc0DF+Ht7oyc4gVyUfpLYS/X yyg348EOtJVTMG0SZtYXpK2yWURcaI9yBVkKOThqQXD4bG1Rd8AmvMpn/m7I2qC6eVF8u/ hFGbQ+itEdYrk4fwJKtK3nlYgBidSLU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-203-Q4pwPJCCOcmmRT7We-A9mg-1; Tue, 26 May 2020 08:50:31 -0400 X-MC-Unique: Q4pwPJCCOcmmRT7We-A9mg-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DD18D461; Tue, 26 May 2020 12:50:29 +0000 (UTC) Received: from horse.redhat.com (ovpn-115-102.rdu2.redhat.com [10.10.115.102]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7C94D10013DB; Tue, 26 May 2020 12:50:29 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id 0988E22036E; Tue, 26 May 2020 08:50:29 -0400 (EDT) Date: Tue, 26 May 2020 08:50:28 -0400 From: Vivek Goyal To: Vitaly Kuznetsov Cc: kvm@vger.kernel.org, x86@kernel.org, Paolo Bonzini , Andy Lutomirski , Thomas Gleixner , Borislav Petkov , "H. Peter Anvin" , Wanpeng Li , Sean Christopherson , Jim Mattson , Gavin Shan , Peter Zijlstra , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/8] KVM: x86: extend struct kvm_vcpu_pv_apf_data with token info Message-ID: <20200526125028.GB108774@redhat.com> References: <20200511164752.2158645-1-vkuznets@redhat.com> <20200511164752.2158645-3-vkuznets@redhat.com> <20200521183832.GB46035@redhat.com> <87sgfq8vau.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87sgfq8vau.fsf@vitty.brq.redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, May 23, 2020 at 06:34:17PM +0200, Vitaly Kuznetsov wrote: > Vivek Goyal writes: > > > On Mon, May 11, 2020 at 06:47:46PM +0200, Vitaly Kuznetsov wrote: > >> Currently, APF mechanism relies on the #PF abuse where the token is being > >> passed through CR2. If we switch to using interrupts to deliver page-ready > >> notifications we need a different way to pass the data. Extent the existing > >> 'struct kvm_vcpu_pv_apf_data' with token information for page-ready > >> notifications. > >> > >> The newly introduced apf_put_user_ready() temporary puts both reason > >> and token information, this will be changed to put token only when we > >> switch to interrupt based notifications. > >> > >> Signed-off-by: Vitaly Kuznetsov > >> --- > >> arch/x86/include/uapi/asm/kvm_para.h | 3 ++- > >> arch/x86/kvm/x86.c | 17 +++++++++++++---- > >> 2 files changed, 15 insertions(+), 5 deletions(-) > >> > >> diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h > >> index 2a8e0b6b9805..e3602a1de136 100644 > >> --- a/arch/x86/include/uapi/asm/kvm_para.h > >> +++ b/arch/x86/include/uapi/asm/kvm_para.h > >> @@ -113,7 +113,8 @@ struct kvm_mmu_op_release_pt { > >> > >> struct kvm_vcpu_pv_apf_data { > >> __u32 reason; > > > > Hi Vitaly, > > > > Given we are redoing it, can we convert "reason" into a flag instead > > and use bit 0 for signalling "page not present" Then rest of the 31 > > bits can be used for other purposes. I potentially want to use one bit to > > signal error (if it is known at the time of injecting #PF). > > Yes, I think we can do that. The existing KVM_PV_REASON_PAGE_READY and > KVM_PV_REASON_PAGE_NOT_PRESENT are mutually exclusive and can be > converted to flags (we'll only have KVM_PV_REASON_PAGE_NOT_PRESENT in > use when this series is merged). > > > > >> - __u8 pad[60]; > >> + __u32 pageready_token; > >> + __u8 pad[56]; > > > > Given token is 32 bit, for returning error in "page ready" type messages, > > I will probably use padding bytes and create pagready_flag and use one > > of the bits to signal error. > > In case we're intended to pass more data in synchronous notifications, > shall we leave some blank space after 'flags' ('reason' previously) and > before 'token'? Given you are planning to move away from using kvm_vcpu_pv_apf_data for synchronous notifications, I will not be too concerned about it. Thanks Vivek