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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F0E35C197A0 for ; Thu, 16 Nov 2023 14:06:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345222AbjKPOGM convert rfc822-to-8bit (ORCPT ); Thu, 16 Nov 2023 09:06:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53602 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231196AbjKPOGJ (ORCPT ); Thu, 16 Nov 2023 09:06:09 -0500 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 656D811F for ; Thu, 16 Nov 2023 06:06:06 -0800 (PST) Received: from lhrpeml500003.china.huawei.com (unknown [172.18.147.200]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4SWMC54dvMz6GDCc; Thu, 16 Nov 2023 22:01:21 +0800 (CST) Received: from lhrpeml500001.china.huawei.com (7.191.163.213) by lhrpeml500003.china.huawei.com (7.191.162.67) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.31; Thu, 16 Nov 2023 14:06:03 +0000 Received: from lhrpeml500001.china.huawei.com ([7.191.163.213]) by lhrpeml500001.china.huawei.com ([7.191.163.213]) with mapi id 15.01.2507.031; Thu, 16 Nov 2023 14:06:03 +0000 From: Salil Mehta To: Cornelia Huck , Jianyong Wu , "maz@kernel.org" , "james.morse@arm.com" , "will@kernel.org" CC: "rmk@armlinux.org.uk" , "suzuki.poulose@arm.com" , "oliver.upton@linux.dev" , "linux-arm-kernel@lists.infradead.org" , "kvmarm@lists.linux.dev" , "linux-kernel@vger.kernel.org" , "justin.he@arm.com" , "jianyong.wu@arm.com" Subject: RE: [PATCH] arm64/kvm: Introduce feature extension for SMCCC filter Thread-Topic: [PATCH] arm64/kvm: Introduce feature extension for SMCCC filter Thread-Index: AQHaGIJSPxqmEiVqkkOrXIqhoEeoZ7B86xkAgAAOImA= Date: Thu, 16 Nov 2023 14:06:03 +0000 Message-ID: <2ea495b04a7d484aa570059298e20862@huawei.com> References: <20231116114152.912344-1-jianyong.wu@arm.com> <877cmhq1zp.fsf@redhat.com> In-Reply-To: <877cmhq1zp.fsf@redhat.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.48.150.188] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > From: Cornelia Huck > Sent: Thursday, November 16, 2023 1:09 PM > To: Jianyong Wu ; maz@kernel.org; james.morse@arm.com; > will@kernel.org > > On Thu, Nov 16 2023, Jianyong Wu wrote: > > > 821d935c87b introduces support for userspace SMCCC filtering, but lack > > of a way to tell userspace if we have this feature. Add a corresponding > > feature extension can resolve this issue. > > > > For example, the incoming feature Vcpu Hotplug needs the SMCCC filter. > > As there is no way to check this feature, VMM will run into error when > > it calls this feature on an old kernel. It's bad for backward compatible. > > Can't you simply query via KVM_HAS_DEVICE_ATTR whether the SMCCC > filtering controls exist? Agreed. In fact, this is what I had earlier intended to do but deferred this change. As of now, RFC V2 of vCPU Hotplug series does not have this check yet while installing the SMCCC filters in KVM Host. Thanks > > Signed-off-by: Jianyong Wu > > --- > > Documentation/virt/kvm/api.rst | 3 ++- > > arch/arm64/kvm/arm.c | 1 + > > include/uapi/linux/kvm.h | 1 + > > 3 files changed, 4 insertions(+), 1 deletion(-) > >