From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sinmsgout01.his.huawei.com (sinmsgout01.his.huawei.com [119.8.177.36]) (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 D9E2937C0F0 for ; Thu, 19 Mar 2026 10:38:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=119.8.177.36 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773916715; cv=none; b=CBnN95xRnJjcLpyHQkcPEWHAHGj8lQXibILvf6d+Jr6h1oVT+Jv1x0CVKVPa7jRgkrbXkT/fEszQw4zfkVZBVMqPnSnpv9NHN8lF5UpUmbFXziojDt88REb3R2JJGmT09CTXuRBtfQ+PQCIAyjIMHmtnYsvqTlGvbbzwVBKXI0o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773916715; c=relaxed/simple; bh=ffuXN//p5iDx8+jkaR2Jg1K5deBAldvp45ErxUHueIE=; h=Date:From:To:CC:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=Qc+jbTlefvvankeVafzpefxJsQ0DvZ8X6e1L8nKyjXJdyPnrymZLAlKLnqOulfjJBWUK8qdwbSqo6PDJSbaVS0F5spsVMzlWy0nPjbRhJtyPohDizHwweCassVzT6FRjOMCXjbppNpTyXt6oePrp57vKbIdTVFFN5yZ1NP7/AdY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b=uY8Tu/+Q; arc=none smtp.client-ip=119.8.177.36 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b="uY8Tu/+Q" 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) Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: lhrpeml100011.china.huawei.com (7.191.174.247) To dubpeml500005.china.huawei.com (7.214.145.207) 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