From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx0b-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (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 19D4E30C158; Tue, 11 Aug 2026 04:53:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.163.158.5 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786424029; cv=none; b=lBRQGfywTGgtdTiIuJazv1UM3StCO0Ui9ZBpUFiMEhrYAiERgIIBO39CoU+dC9eW+IxQ6UIjS2uSgFW4qPfxygpd2QanqzRosM17wC+IJDA0TN30jPOSsPAAgq4FK8Zc/xOVG/I7Bv8E3ZK3z3qt265EOfOJpr7nSHXyB8eYfsc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786424029; c=relaxed/simple; bh=MwJNYXoyFbP4fg9agJMM1tx/XmDkciolpPgOUDkLGY0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=O6OmCbG/wAELAoKHJa87pLYlZCoEvzNNrK30Hu1NyAso/UFnkX82Fug5zAZKPrJhjpKkQSqLQkqLtGqJ5/w1poDKepi2HAkNdjByh+GYCw4ILrMKq9er194zOtp8NCVyNUVtaI7KSvmTfGRZlAxzOzvPee8C6LIhFMEsnvncAjg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com; spf=pass smtp.mailfrom=linux.ibm.com; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b=gy9QzwTd; arc=none smtp.client-ip=148.163.158.5 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b="gy9QzwTd" Received: from pps.filterd (m0360072.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 67AN1anN2999512; Tue, 11 Aug 2026 04:53:32 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc :content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=pp1; bh=uz20XD LJ01Y33lENru859JzA8c0KdEFgFXjsz3QA39w=; b=gy9QzwTdg2DogRibWkmjO7 gQeH7jTlre3WnTugCjxdxzNZU1ocIDE/cJRvgC0a9AI3BKJmlDCM3aT4pEEftecn UGNV4y7NWpX/LiobkjmnnkABbyLGa7wiSAGJvcf7wVkO4bQxoIjD05eHlMnF9rLm nF1HZxWW2W51cSI5yIz1BTla5QgTAta4HIuZc/GM0aLnKi9ft9F1bfHTJXUEcsvA tHvMW+VNbHepWqRhBAQoRnPdQCcnc/8VJ2BiXH95qjoh1ApbQt5jwy28aSGZ62SS HexgLnoAOd1zl9pdZafP7OLphez8ViM6JBMas0IvbXNVMrlwQCb338HnJntST50g == Received: from ppma11.dal12v.mail.ibm.com (db.9e.1632.ip4.static.sl-reverse.com [50.22.158.219]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 4fwvnw2qym-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 11 Aug 2026 04:53:32 +0000 (GMT) Received: from pps.filterd (ppma11.dal12v.mail.ibm.com [127.0.0.1]) by ppma11.dal12v.mail.ibm.com (8.18.1.7/8.18.1.7) with ESMTP id 67B4fOut029529; Tue, 11 Aug 2026 04:53:31 GMT Received: from smtprelay04.fra02v.mail.ibm.com ([9.218.2.228]) by ppma11.dal12v.mail.ibm.com (PPS) with ESMTPS id 4fxhfxyc62-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 11 Aug 2026 04:53:31 +0000 (GMT) Received: from smtpav01.fra02v.mail.ibm.com (smtpav01.fra02v.mail.ibm.com [10.20.54.100]) by smtprelay04.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 67B4rRrq9961908 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 11 Aug 2026 04:53:27 GMT Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3E2A520043; Tue, 11 Aug 2026 04:53:27 +0000 (GMT) Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2066C20040; Tue, 11 Aug 2026 04:53:22 +0000 (GMT) Received: from Linuxdev.ibmuc.com (unknown [9.43.82.57]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 11 Aug 2026 04:53:21 +0000 (GMT) From: Madhavan Srinivasan To: linuxppc-dev@lists.ozlabs.org, Amit Machhiwal Cc: Vaibhav Jain , Anushree Mathur , Paolo Bonzini , Nicholas Piggin , Michael Ellerman , "Christophe Leroy (CS GROUP)" , Jonathan Corbet , Shuah Khan , Ritesh Harjani , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Harsh Prateek Bora , Gautam Menghani Subject: Re: [PATCH v9 0/4] KVM: PPC: Expose CPU compatibility modes for nested guests Date: Tue, 11 Aug 2026 10:23:20 +0530 Message-ID: <178642395406.173296.2879693080941807837.b4-ty@linux.ibm.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260808161148.66673-1-amachhiw@linux.ibm.com> References: <20260808161148.66673-1-amachhiw@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=RsP16imK c=1 sm=1 tr=0 ts=6a7aaacc cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VwQbUJbxAAAA:8 a=BDvn-t7a7rEMPqDFjeMA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: LA6sxo_RISA67hFYdRaOcN7AXdgANatr X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODExMDAzNSBTYWx0ZWRfXw0ry2qiISU9z 49OfTxVCoBsf8kvekQQgmR8+y0VzUO4+E5+nk9tJj0RiIkI4AwNcPH/jdsoi75WYbAN7Baocdrz rZJG9kpOW41UOpFwbvUaByM6L3+aDoctT0dhIvL1D9GkH8pi+Urv7+b8yYjN6RxDGdpWKh79XSZ kijkk8MRllEEQqvCbd5LciiJL7u6bwqe7Co3ZFagJDjMi6618MqT83YwamB/VqZOCmtcyFUYStP av6ckDEKqvB4mrKU+J7UvpDvLBQLKoIv3/ffVE03Iow8eXnvqnNVpPC4DpeeMqkeAfRoA/0aD3d kMoI2t74vAIBZz5N4cmU/vYS0RZ/1K1K/aKn/j4eV6cjTkttJQtGCUz+G7XCA06niQZs72jsvyq ppAZlzbZhy6saSWIvx3NRj7o/S5kxzzOH/mcEHeJoPNT1dQd8u9y7pIv8zN8AjctFldmqE504SL VADKv/8LmImqaFowJuQ== X-Proofpoint-ORIG-GUID: YER50ExlspIYVf_Aop3_3rI5pD7C4iSZ X-Proofpoint-Spam-Info: AW1haW4tMjYwODExMDAzNSBTYWx0ZWRfX0ZQEAAwLF04R 4IGvQD8K76Dm0Ci2t/OFVOIZcyUf/dJKH9C4YI6HJJ41PRKVHc+2OZs0Sxks6FSR5MTsX0oJQCc ZaXJ75gUVaQvq0Wrrbs1zyzT7iSDpuU= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-10_06,2026-08-10_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 impostorscore=0 suspectscore=0 clxscore=1015 malwarescore=0 phishscore=0 adultscore=0 lowpriorityscore=0 priorityscore=1501 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608110035 On Sat, 08 Aug 2026 21:41:44 +0530, Amit Machhiwal wrote: > On POWER systems, newer processor generations can operate in compatibility > modes corresponding to earlier generations (e.g., a Power11 system running > in Power10 compatibility mode). In such cases, the effective CPU level > exposed to guests differs from the physical processor generation. > > This creates a problem for nested virtualization. When booting a nested KVM > guest (L2) inside a host KVM guest (L1) running in a compatibility mode, > userspace (e.g., QEMU) may derive the CPU model from the raw hardware PVR > and attempt to configure the nested guest accordingly. However, the L1 > partition is constrained by the compatibility level negotiated with the > hypervisor (L0), and requests exceeding that level are rejected, leading to > guest boot failures such as: > > [...] Applied to powerpc/next. [1/4] KVM: PPC: Introduce KVM_CAP_PPC_COMPAT_CAPS and wire up ioctl https://git.kernel.org/powerpc/c/ac3e65ddddf3128c1f0c2187889fab458fcf4a70 [2/4] KVM: PPC: Book3S HV: Implement compat CPU capability retrieval for KVM on PowerVM https://git.kernel.org/powerpc/c/b76fb087efcdaf6eb5c2c6c5e53c763640fc4b02 [3/4] KVM: PPC: Book3S HV: Add support for compat CPU capabilities for KVM on PowerNV https://git.kernel.org/powerpc/c/8735048f54ec827102dcbd757a6c1c1e02613fc4 [4/4] KVM: PPC: Document KVM_PPC_GET_COMPAT_CAPS ioctl https://git.kernel.org/powerpc/c/c1721e584244ff79a593d6f0ad0405a2e07b765a cheers