From patchwork Wed Jun 12 02:35:51 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Shaoqin Huang X-Patchwork-Id: 13694379 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 4F759C27C79 for ; Wed, 12 Jun 2024 02:36:37 +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: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Skhula7518PMXu1UZDnu+UyfH0UgWPzNpluBrfVr+JQ=; b=R6T1zhVFABnTTh7z4e0fQpqdO0 fk4dlmHMAvi7n8cWb7fPjNx5ntSOqna+WOv5IhjjwuRBncnezDL/3MODYTbAiF31GloJdnBtaezQJ GO+W9TFxq3VvGBIN+6CD4G0q6qPDfVS0pJDC3sCaPxYwGmcTkch9eUgVNHn+XjtdlQb7LUmSdI+fO /5PUtd2pyTRzSOZd6BEZmgBM6gNqPlz/0l+kRs3dkvXhalK1DHpdts/zJ+tyVwf8wE0Q7LX6zbFEA FxPeUf6KA+YE8imPlVz3yQGVAX4sFYO6gEDj+5vFGBTvf9k9gcEAX3zS9fVhS/FnBq8ZDWkAcY8Sb s94ZMyaQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sHDqZ-0000000Ap2F-2gyK; Wed, 12 Jun 2024 02:36:23 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sHDqU-0000000Ap0I-3iaT for linux-arm-kernel@lists.infradead.org; Wed, 12 Jun 2024 02:36:20 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1718159778; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Skhula7518PMXu1UZDnu+UyfH0UgWPzNpluBrfVr+JQ=; b=c+bmHwKF1XRHa3F8EuNtKFO6BsO1Uyb1U3JP6dBDww9DH2xXTJ2AR8jvSBy+5+CB4C0HwT zsiz/CLv3woIw9jUb26tr+EcdLRKQRkGHQutHOckLHbt7eYQtZWIAuMHX5V+jnCyvGDVSo tHYBas+R6vgO6d8Xyw5n0d7EBXhRyLk= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-149-5a8JObh9M8incYscAze6kQ-1; Tue, 11 Jun 2024 22:36:08 -0400 X-MC-Unique: 5a8JObh9M8incYscAze6kQ-1 Received: from mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.40]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0564C19560AB; Wed, 12 Jun 2024 02:36:06 +0000 (UTC) Received: from virt-mtcollins-01.lab.eng.rdu2.redhat.com (virt-mtcollins-01.lab.eng.rdu2.redhat.com [10.8.1.196]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 6E96719560AF; Wed, 12 Jun 2024 02:36:03 +0000 (UTC) From: Shaoqin Huang To: Oliver Upton , Marc Zyngier , kvmarm@lists.linux.dev Cc: Eric Auger , Sebastian Ott , Cornelia Huck , Shaoqin Huang , James Morse , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [RFC PATCH v1 1/2] KVM: arm64: Allow BT field in ID_AA64PFR1_EL1 writable Date: Tue, 11 Jun 2024 22:35:51 -0400 Message-Id: <20240612023553.127813-2-shahuang@redhat.com> In-Reply-To: <20240612023553.127813-1-shahuang@redhat.com> References: <20240612023553.127813-1-shahuang@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240611_193619_017843_39958465 X-CRM114-Status: GOOD ( 16.16 ) 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 When migrating from MtCollins to AmpereOne, the BT field value in ID_AA64PFR1_EL1 register is different and not writable. This causes the migration to fail. The BT field means Branch Target Identification mechanism support in AArch64 state. The value 0 means BT is not implemented, the value 1 means BT is implemented. On MtCollins(Migration Src), the BT value is 0. On AmpereOne(Migration Dst), the BT value is 1. As it defined in the ftr_id_aa64dfr0, the samller value is safe. So if we make the BT field writable, on the AmpereOne(Migration Dst) the BT field will be overrided with value 0. Signed-off-by: Shaoqin Huang --- But there is a question, the ARM DDI mentions from Armv8.5, the only permitted value is 0b01. Do you guys know if there are any consequence if the userspace write value 0b0 into this field? Or we should restrict that at some level, like in VMM or kernel level? --- arch/arm64/kvm/sys_regs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index c9f4f387155f..8e0ea62e14e1 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -2292,7 +2292,7 @@ static const struct sys_reg_desc sys_reg_descs[] = { ID_AA64PFR0_EL1_GIC | ID_AA64PFR0_EL1_AdvSIMD | ID_AA64PFR0_EL1_FP), }, - ID_SANITISED(ID_AA64PFR1_EL1), + ID_WRITABLE(SYS_ID_AA64PFR1_EL1, ID_AA64PFR1_EL1_BT), ID_UNALLOCATED(4,2), ID_UNALLOCATED(4,3), ID_WRITABLE(ID_AA64ZFR0_EL1, ~ID_AA64ZFR0_EL1_RES0),