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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 2FD48C3ABC3 for ; Tue, 13 May 2025 15:57:44 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uEs08-0003T1-A6; Tue, 13 May 2025 11:57:04 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uEs07-0003SY-Kx for qemu-devel@nongnu.org; Tue, 13 May 2025 11:57:03 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uEs04-0001Ay-Ed for qemu-devel@nongnu.org; Tue, 13 May 2025 11:57:03 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1747151819; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to: references:references; bh=DEFG/nsmaD+Qs87+Cs7UWCDQ+3GwoOekcLYQ3v155tY=; b=TcDNc0zETe/7XjfvyZYiXwqsDLXEw9fb95uN2eZlC+tonkMC7yjHD8M8aMHkjiIlnirhc6 IQ5J1bwIk9Y1u51aUX8C1wSSc9y3k+UNcaC4xyo0e+Vqzvoe2UCLDEiIxIConrxFD028sF f8EVyjsASLjdvn2EZzIWL42nOuuOzoM= Received: from mx-prod-mc-01.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-582-niJYAd0zMdu9vAJhOR_wng-1; Tue, 13 May 2025 11:56:56 -0400 X-MC-Unique: niJYAd0zMdu9vAJhOR_wng-1 X-Mimecast-MFC-AGG-ID: niJYAd0zMdu9vAJhOR_wng_1747151812 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 42CCB195DE39; Tue, 13 May 2025 15:56:51 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.110]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 19A941953B82; Tue, 13 May 2025 15:56:40 +0000 (UTC) Date: Tue, 13 May 2025 16:56:36 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Cornelia Huck Cc: eric.auger.pro@gmail.com, eric.auger@redhat.com, qemu-devel@nongnu.org, qemu-arm@nongnu.org, kvmarm@lists.linux.dev, peter.maydell@linaro.org, richard.henderson@linaro.org, alex.bennee@linaro.org, maz@kernel.org, oliver.upton@linux.dev, sebott@redhat.com, shameerali.kolothum.thodi@huawei.com, armbru@redhat.com, abologna@redhat.com, jdenemar@redhat.com, agraf@csgraf.de, shahuang@redhat.com, mark.rutland@arm.com, philmd@linaro.org, pbonzini@redhat.com Subject: Re: [PATCH v3 08/10] arm/cpu: more customization for the kvm host cpu model Message-ID: References: <20250414163849.321857-1-cohuck@redhat.com> <20250414163849.321857-9-cohuck@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250414163849.321857-9-cohuck@redhat.com> User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.549, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Apr 14, 2025 at 06:38:47PM +0200, Cornelia Huck wrote: > From: Eric Auger > > If the interface for writable ID registers is available, expose uint64 > SYSREG properties for writable ID reg fields exposed by the host > kernel. Properties are named SYSREG__ with REG and FIELD > being those used in linux arch/arm64/tools/sysreg. This done by > matching the writable fields retrieved from the host kernel against the > generated description of sysregs. > > An example of invocation is: > -cpu host,SYSREG_ID_AA64ISAR0_EL1_DP=0x0 > which sets DP field of ID_AA64ISAR0_EL1 to 0. Functionally this works, but stylewise it is rather too verbose IMHO. I understand this aims to mtch the arm feature names, but we can at least drop the SYSREG_ prefix here which IMHO doesn't add much value. The component only has a small number of possible prefixes, so it seems pretty unlikely we would get a name clash between these and some other QOM property. Also could we stick with lowercase, rather than uppercase. I appreciate the spec uses uppercase, but that doesn't concern itself with end user usage. If we just plain transform everything to lowercase, there's still a clear mapping to the spec that people will understand [1]. This example uses '-cpu host', but does this also work with '-cpu max' ? Conceptually '-cpu max' is supposed to be functionally identical to '-cpu host' when KVM is enabled. Obviously you'd ned to exclude it from '-cpu max' with TCG or other non-KVM accels. > +/* > + * decode_idreg_writemap: Generate props for writable fields > + * > + * @obj: CPU object > + * @index: index of the sysreg > + * @map: writable map for the sysreg > + * @reg: description of the sysreg > + */ > +static int > +decode_idreg_writemap(Object *obj, int index, uint64_t map, ARM64SysReg *reg) > +{ > + int i = ctz64(map); > + int nb_sysreg_props = 0; > + > + while (map) { > + > + ARM64SysRegField *field = get_field(i, reg); > + int lower, upper; > + uint64_t mask; > + char *prop_name; > + > + if (!field) { > + /* the field cannot be matched to any know id named field */ > + warn_report("%s bit %d of %s is writable but cannot be matched", > + __func__, i, reg->name); > + warn_report("%s is cpu-sysreg-properties.c up to date?", __func__); What scenario triggers this warning ? Is this in relation to QEMU auto-detecting host CPU features, as opposed to user -cpu input ? > + map = map & ~BIT_ULL(i); > + i = ctz64(map); > + continue; > + } > + lower = field->lower; > + upper = field->upper; > + prop_name = g_strdup_printf("SYSREG_%s_%s", reg->name, field->name); > + trace_decode_idreg_writemap(field->name, lower, upper, prop_name); > + object_property_add(obj, prop_name, "uint64", > + get_sysreg_prop, set_sysreg_prop, NULL, field); > + nb_sysreg_props++; > + > + mask = MAKE_64BIT_MASK(lower, upper - lower + 1); > + map = map & ~mask; > + i = ctz64(map); > + } > + trace_nb_sysreg_props(reg->name, nb_sysreg_props); > + return 0; > +} > + > +/* analyze the writable mask and generate properties for writable fields */ > +void kvm_arm_expose_idreg_properties(ARMCPU *cpu, ARM64SysReg *regs) > +{ > + int i, idx; > + IdRegMap *map = cpu->writable_map; > + Object *obj = OBJECT(cpu); > + > + for (i = 0; i < NR_ID_REGS; i++) { > + uint64_t mask = map->regs[i]; > + > + if (mask) { > + /* reg @i has some writable fields, decode them */ > + idx = kvm_idx_to_idregs_idx(i); > + if (idx < 0) { > + /* no matching reg? */ > + warn_report("%s: reg %d writable, but not in list of idregs?", > + __func__, i); > + } else { > + decode_idreg_writemap(obj, i, mask, ®s[idx]); > + } > + } > + } > +} > + With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|