From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 B2C15188917 for ; Mon, 28 Oct 2024 16:00:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730131262; cv=none; b=RiT/rWFqh+aebSfzVrhki71kqQ79KHCpDVSoeIeADsFeDvuAVdv+mdFxZ5lo7vmq5blGEk/d65XsUOgeKhJG78KFvODw4HNb+EbyMnQGvF9FdcV0AfAUIyFgHDaHlTPUwtVIvt77CfMlzjshEcgkGUxeDsb5Q5s22sClQCP2KT8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730131262; c=relaxed/simple; bh=rKMt39/IMn9ntx86rLiJJxC2lha3ViI6YIHGMus7n4k=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=slt9oXOjEDKanEj866v735akKGMJjC4MghKFB2pvQuAkD3za7xcLYFKHCIXwfzZscgtwXPpP64udzlGlCg9K7akpt3lxfxfTPWYVtQWoGmffuTepFzCWH6gw1juNTwao0aX00z7dOmV2otV4wGt+zgonOQiv2FDhrmmXdNj2xus= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=fM+xSrXM; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="fM+xSrXM" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1730131258; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=P9xxfVBBFS3vGf2amIpYTb6y6yA1Jac+htCBbXKyA58=; b=fM+xSrXMwBnMcongAh9DYFPeFLJa8eP0o18grrBad/VoemTwkN0XoDQMHvwH5yJy1R7Amr TtSBgZzRWi8EpTrCRSg8gp8oTZxmDC7VaGXilVjSWeQdvKgmLE2DtakmkU73Fe26cl99Va HlSE5LnQG8qkD/ZQdm6vi5NWfdyDPkI= 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-627-UW8mt4UnNCKclBnsbgKa7A-1; Mon, 28 Oct 2024 12:00:55 -0400 X-MC-Unique: UW8mt4UnNCKclBnsbgKa7A-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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 62DD3195608C; Mon, 28 Oct 2024 16:00:52 +0000 (UTC) Received: from localhost (unknown [10.22.88.106]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E70AC19560AA; Mon, 28 Oct 2024 16:00:49 +0000 (UTC) From: Cornelia Huck To: =?utf-8?Q?Daniel_P=2E_Berrang=C3=A9?= , Eric Auger Cc: eric.auger.pro@gmail.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, shahuang@redhat.com, mark.rutland@arm.com, philmd@linaro.org, pbonzini@redhat.com Subject: Re: [RFC 18/21] arm/cpu: Introduce a customizable kvm host cpu model In-Reply-To: Organization: "Red Hat GmbH, Sitz: Werner-von-Siemens-Ring 12, D-85630 Grasbrunn, Handelsregister: Amtsgericht =?utf-8?Q?M=C3=BCnchen=2C?= HRB 153243, =?utf-8?Q?Gesch=C3=A4ftsf=C3=BChrer=3A?= Ryan Barnhart, Charles Cachera, Michael O'Neill, Amy Ross" References: <20241025101959.601048-1-eric.auger@redhat.com> <20241025101959.601048-19-eric.auger@redhat.com> User-Agent: Notmuch/0.38.3 (https://notmuchmail.org) Date: Mon, 28 Oct 2024 17:00:46 +0100 Message-ID: <871q00p68h.fsf@redhat.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 On Fri, Oct 25 2024, Daniel P. Berrang=C3=A9 wrote: > On Fri, Oct 25, 2024 at 03:18:25PM +0200, Eric Auger wrote: >> Hi Daniel, >>=20 >> On 10/25/24 15:06, Daniel P. Berrang=C3=A9 wrote: >> > On Fri, Oct 25, 2024 at 12:17:37PM +0200, Eric Auger wrote: >> >> At the moment, the custom model does not support legacy options >> >> of the host cpu model. We need to understand what we do with those >> >> latter (SVE, ...). This means that related KVM ioctl are >> >> not called yet. >> > It will be pretty painful to have to use different feature >> > terminology for different CPU models. Everything in libvirt >> > assuming feature terminology varies per-arch, not per-CPU >> > model. >> Actually as far as I understand those regids/fields would fit all kind >> of aarch64 Cortex-A CPUs. So they wouldn't vary per-CPU (I mean their >> terminology. Their availability will). > > What I mean is can we define named models for various different > vendor's Cortex-A silicon and just use that without needing to > toggle features, except in rare cases. I'm not sure whether creating named models for various cpus would actually scale; what we probably could do is come up with some Armv8.6, Armv8.7, ... models and have additional models for some well-known cpus. That would also give us some basic sanity checks for feature combinations, if we do not want to support completely custom frankencpus.