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 57799C79FB9 for ; Thu, 10 Sep 2026 12:59:35 +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:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=NWHtsCUiemcaNOw8QS78Dn5hbjWnozO6hfjd10/VVAU=; b=UZQXCgXQnX0PV3OzpBhqMcZCsZ QeJ9TZznqEMIT8utftmFyrHR0c88j6514ECl8ASqFom3OlqKzZqa923QeKWpjWhF1NZK3jlJmdZ2Z l0oY3S8fqaL8HINucRKTuZQnTrwegjjjk2OoGReu9J/0PIxCbNMyq4o7HVHe6ohW8tDIRTGV05+ZX zQNVuJqWQNro7b1W44OTgnHdzPKwa8Ph48jyMrS0oSMGNTn20Ai+yumlKNHApHDfCITCnY/II8HW0 tHJEZpQG0ApCRBMmbOl3e4t1Q0X9L8L9h7nqiTdBiYmXDIzur/av2eSXpaAP+fjCm3+cLW6XKM017 l+cMcJvA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x4e8q-0000000EMm0-33hn; Thu, 10 Sep 2026 12:44:36 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x4e8o-0000000EMld-24cT for linux-arm-kernel@lists.infradead.org; Thu, 10 Sep 2026 12:44:35 +0000 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 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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260910_054434_576839_7A8A0B9B X-CRM114-Status: GOOD ( 15.18 ) 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 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