From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 37596488D84; Thu, 10 Sep 2026 12:44:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789044275; cv=none; b=C/eCEUzbWAeZYA6NUAlPej9PdgC5fgGYlJx6HHp0xeKLoA3x1MefG62c0B0/XDCCPJULXcJeQMB2c73zQiT5ZZetaulsCTy/1PYSp5UA3/RnwW883GHimreouZGHBLKmn3nPdLRulM11lxW8tR7mCHlCoQ9gSXVX1GqM91fWO/Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789044275; c=relaxed/simple; bh=mWkbpWT4DcWBDnuPciUuXTxSlxhpPhycuu8HUKXHUOA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=laple+TAiIngEtYe57gw72HVZqB5EvsNydV8/vsBw0yzWJy4ipe2k7iL7XQkiO2w6WxoQctHO6c9fXhcjEXUKOZQ6e9IwQ4tr+rPuwayb7h77bL6NbDs0BWvsaqA4bVJSJRH0dbU9mGC5MFQLjLqirg0WWwHxyOrwBEyeCbkr54= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=SLmLCa+f; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="SLmLCa+f" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DA328153B; Thu, 10 Sep 2026 05:44:27 -0700 (PDT) Received: from [10.2.197.99] (ewhatever.cambridge.arm.com [10.2.197.99]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2C66C3F7B4; Thu, 10 Sep 2026 05:44:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1789044271; bh=mWkbpWT4DcWBDnuPciUuXTxSlxhpPhycuu8HUKXHUOA=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=SLmLCa+f5BtxsTBKm8tudDDP9I7m2Cg/u7128g6wS0ro1bz11aFjbBGu9n2eIc41B FUtlcYL2cz0Ua7c9tQZiKMZrQEHR995V9VnblJ8o99wKmNn9v9nIsWoV87xmmnPX4v 5teVkErMcFb7+nGSTnihU+gv7YTvkrknmBC8DZxk= Message-ID: Date: Thu, 10 Sep 2026 13:44:26 +0100 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v17 10/20] KVM: arm64: coco: Disable Steal time accounting for coco guests To: Fuad Tabba Cc: kvm@vger.kernel.org, kvmarm@lists.linux.dev, maz@kernel.org, will@kernel.org, catalin.marinas@arm.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, steven.price@arm.com, aneesh.kumar@kernel.org, oupton@kernel.org, gshan@redhat.com, joey.gouly@arm.com, yuzenghui@huawei.com, linux-coco@lists.linux.dev, gankulkarni@os.amperecomputing.com, sdonthineni@nvidia.com, alpergun@google.com, fj0570is@fujitsu.com, WeiLin.Chang@arm.com, lpieralisi@kernel.org, enju.kohei@fujitsu.com References: <20260908162223.1683432-1-suzuki.poulose@arm.com> <20260908162223.1683432-11-suzuki.poulose@arm.com> <6152fc41-65f0-460f-90b4-1454c11bcba6@arm.com> Content-Language: en-US From: Suzuki K Poulose In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10/09/2026 13:42, Fuad Tabba wrote: > Hi Suzuki, > > On Thu, 10 Sept 2026 at 11:28, Suzuki K Poulose wrote: > ... >> Just to make sure I understand the picture: >> >> For coco VMs: >> >> - check extension on coco KVM, KVM_CAP_STEAL_TIME => 0 >> >> And a follow up DEVICE_HAS_ATTR => -EPERM ? >> >> But we tell the VMM, look you don't have the capabilit on this VM. >> But if you try to set the attribute isn't it more appropriate to >> say: >> -ENXIO - No you don't have that feature on this VM (-ENXIO) >> rather than >> -EPERM - No, I won't let you do that. >> >> Remember we are doing only in the "VM" context. It is a minor nit >> but I wanted to make sure we understand what we are thinking. > > -ENXIO it is. I went back to api.rst for KVM_SET_DEVICE_ATTR: ENXIO is > for a group or attribute that's "unknown/unsupported for this device", > and EPERM for one that "cannot (currently) be accessed this way", a > state or access-mode refusal, so a VM type that doesn't have the > feature is the former. KVM_HAS_DEVICE_ATTR only documents ENXIO at > all. Your patch is good as it is. > > Reviewed-by: Fuad Tabba Cheers, Suzuki