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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8672FD74961 for ; Wed, 30 Oct 2024 04:41:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=sp/Joqr6Fg+CbM6kllKhe4k7VezD6hpv2eBeT+NpJcM=; b=Z/eL9xS5B77tVbH248dpNs/W7w 6A55TXRubS2U0lpwfc0CKYoADloCn+cpdNaN4NZuFxUWSsPlSF8Cw6jGuuqJMyCmUgTAUpZFqM4gK IcxWlCFSMq9lf7IqU0FivjNwCauGy3W15NkH2bXGsj9yud8OZRyJ6sggM4kLS2rth8tqiNJVGUXBz VHdUs/d0TAg000lSgUBz3DtETpUvEOwb7CZYQdOIKPnur14TRGsD5WNOED/5IH+i+RqhDDSGknk9z JdGUALScKq7JhpyrMIDm8lZXpa6f/szPFfFksmQpwJyA5Am+l5SKH6PB9qc10a8pL93FFPA50h8Dn ysn9zNCw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1t60W2-0000000Ggti-1zTk; Wed, 30 Oct 2024 04:41:06 +0000 Received: from out-176.mta0.migadu.com ([2001:41d0:1004:224b::b0]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1t60UO-0000000GgkC-0lvJ for linux-arm-kernel@lists.infradead.org; Wed, 30 Oct 2024 04:39:25 +0000 Date: Tue, 29 Oct 2024 21:39:14 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1730263162; 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=sp/Joqr6Fg+CbM6kllKhe4k7VezD6hpv2eBeT+NpJcM=; b=PoMWjfHlTy7H6Q3L8P7djXveyvh0HGtnyk/fdVX3t5Pr3Kp2rNPy1w8a5UNt0sUPepSSq4 +O8NZl5UbPoxtVfPZnQgBadyXzdKzIDT+f4n2hZ0etV8o24RHVM6WBDO9nAO+MWMhzpAlD +zggZT7wSclLJEi+pg2CAIbdT5Mv0iI= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Oliver Upton To: Shameerali Kolothum Thodi Cc: "kvmarm@lists.linux.dev" , "maz@kernel.org" , "catalin.marinas@arm.com" , "will@kernel.org" , "mark.rutland@arm.com" , "cohuck@redhat.com" , "eric.auger@redhat.com" , yuzenghui , "Wangzhou (B)" , jiangkunkun , Jonathan Cameron , Anthony Jebson , "linux-arm-kernel@lists.infradead.org" , Linuxarm Subject: Re: [RFC PATCH v2 1/3] KVM: arm64: Add hypercall support for retrieving migration targets Message-ID: References: <20241024094012.29452-1-shameerali.kolothum.thodi@huawei.com> <20241024094012.29452-2-shameerali.kolothum.thodi@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241029_213924_555596_79D60F2D X-CRM114-Status: GOOD ( 15.28 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Oct 29, 2024 at 04:00:39PM +0000, Shameerali Kolothum Thodi wrote: > > We can't treat a single register as both a signed quantity *and* a full > > 64 bits of bitfields. Maybe just scrap the version and have this thing > > either return a negative error or positive quantity of implementations. > > Ok. I had a look at PV_TIME_ST/ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID > and got that idea. Separate registers make sense though. > > Do we really need to skip the version number? The idea was to use that as a > future proof for data format in case we realize that MIDR/REVIDR is not good > enough for errata later. That is definitely an approach we can take. The alternative I had in mind was that we'd allocate a new function ID if we needed to break ABI to correct shortcomings of the original interface. -- Thanks, Oliver