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 C3BE8108E1E2 for ; Thu, 19 Mar 2026 10:38:44 +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:MIME-Version:References:In-Reply-To:Message-ID:Subject:CC:To: From:Date:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=G/yWvs+u+2ox5r2RC2KJBHK3Mv2sQaP76wNy2i2+g+k=; b=io1XNXMRaulDUP7Y6QJ5sSOvrV d9QrJrdij8kS5jePNntAhmek0TSj5iWiFB0LvGd/Xz3FbNK2eaFNPXQoHDTnu7VI3Lae4bN2Me3Fz EfDtT7+sam5giny27xqp1ZMLb4D8eA+Ckl9dfIs5MOQONaAJsrOOAyamfy+awMf7ZBtww49Qy0uah 9eo3qwnuL9qdF/MFRsR6LkO7D5/weA+ygFGVRWTMXBAXtLZ8bGLUOG5GiFgYZsTyyUl3/bhtp3sGa GLPuVoUQq+aCIwEntryshZB1FZT8noY+ynbsD2yXkzaEWVAGR9tX9rvqqj+Ogs513vQoThVuDkNyf 2qFwwpsA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1w3Alz-0000000AQgE-3K2F; Thu, 19 Mar 2026 10:38:39 +0000 Received: from sinmsgout01.his.huawei.com ([119.8.177.36]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1w3Alx-0000000AQfi-08E0 for linux-arm-kernel@lists.infradead.org; Thu, 19 Mar 2026 10:38:38 +0000 dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=G/yWvs+u+2ox5r2RC2KJBHK3Mv2sQaP76wNy2i2+g+k=; b=uY8Tu/+QmqJx89Fu6/4iVzerjZ3SA/lL2P6iA/PuYikQcxBBeLzHAIqhAMhEjNnlm1Pb8XU6F /cPLkPqSi8oMF3fwYxG/tvlc/e8EhrbsTGH6L87Wk9k8LlYEHhZsrtSJYOcefmMYK1o4GmKCt+J xc1w3GFBFN+p1lXGaE6uncE= Received: from frasgout.his.huawei.com (unknown [172.18.146.32]) by sinmsgout01.his.huawei.com (SkyGuard) with ESMTPS id 4fc2Bd5VDGz1P7Fp; Thu, 19 Mar 2026 18:34:49 +0800 (CST) Received: from mail.maildlp.com (unknown [172.18.224.150]) by frasgout.his.huawei.com (SkyGuard) with ESMTPS id 4fc2GN5cxDzHnH8Z; Thu, 19 Mar 2026 18:38:04 +0800 (CST) Received: from dubpeml500005.china.huawei.com (unknown [7.214.145.207]) by mail.maildlp.com (Postfix) with ESMTPS id 1CD524056A; Thu, 19 Mar 2026 18:38:28 +0800 (CST) Received: from localhost (10.203.177.15) by dubpeml500005.china.huawei.com (7.214.145.207) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Thu, 19 Mar 2026 10:38:27 +0000 Date: Thu, 19 Mar 2026 10:38:26 +0000 From: Jonathan Cameron To: Sascha Bischoff CC: "linux-arm-kernel@lists.infradead.org" , "kvmarm@lists.linux.dev" , "kvm@vger.kernel.org" , nd , "maz@kernel.org" , "oliver.upton@linux.dev" , Joey Gouly , Suzuki Poulose , "yuzenghui@huawei.com" , "peter.maydell@linaro.org" , "lpieralisi@kernel.org" , Timothy Hayes Subject: Re: [PATCH v6 14/39] KVM: arm64: gic-v5: Trap and emulate ICC_IDR0_EL1 accesses Message-ID: <20260319103826.00004be1@huawei.com> In-Reply-To: <20260317113949.2548118-15-sascha.bischoff@arm.com> References: <20260317113949.2548118-1-sascha.bischoff@arm.com> <20260317113949.2548118-15-sascha.bischoff@arm.com> X-Mailer: Claws Mail 4.3.0 (GTK 3.24.42; x86_64-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.203.177.15] X-ClientProxiedBy: lhrpeml100011.china.huawei.com (7.191.174.247) To dubpeml500005.china.huawei.com (7.214.145.207) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260319_033837_252937_8F97AD3B X-CRM114-Status: UNSURE ( 9.76 ) X-CRM114-Notice: Please train this message. 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, 17 Mar 2026 11:43:34 +0000 Sascha Bischoff wrote: > Unless accesses to the ICC_IDR0_EL1 are trapped by KVM, the guest > reads the same state as the host. This isn't desirable as it limits > the migratability of VMs and means that KVM can't hide hardware > features such as FEAT_GCIE_LEGACY. > > Trap and emulate accesses to the register, and present KVM's chosen ID > bits and Priority bits (which is 5, as GICv5 only supports 5 bits of > priority in the CPU interface). FEAT_GCIE_LEGACY is never presented to > the guest as it is only relevant for nested guests doing mixed GICv5 > and GICv3 support. > > Signed-off-by: Sascha Bischoff Does what I'd expect. Reviewed-by: Jonathan Cameron