From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-180.mta0.migadu.com (out-180.mta0.migadu.com [91.218.175.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6CF958F58 for ; Wed, 30 Oct 2024 04:39:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.180 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730263166; cv=none; b=jNPv08iayA0lQ8el38OlaRZrJCEenLNYiU+LaIdk3cXIDjXIPYXVsV4EiQ5oXHiEGV3ACBMEE3Bt1KRbZZnf0wAHYDJkpTf1wbUfGq+GHuA/4Q+lg1E22QMUPwbY+QDrzgm/e6nRCoR4HRLQP7LqC774H3ustDCraZmHC5lvYW8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730263166; c=relaxed/simple; bh=cRtjpOFnK3lIH2p96pKrXOJJhMgj+bCnppTJtPLmW/g=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=GfmxO+AFXSJvzY1vO6IBM5+J2G6pZBKsFXmxAPKdaedEXZ3p9vys8ktOdbDlls4s9OtetTB/eCqMEVeLMkP2ixEzjtLgDa/SsAZ458YWmBGOMf/sZHjcR7cSYyQcwGu/VoDnl6cqrhj7s6VEoCCZDG47AKdVmpqSuuIfeIxchn4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=PoMWjfHl; arc=none smtp.client-ip=91.218.175.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="PoMWjfHl" 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> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT 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