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 7611B4F5DFE for ; Thu, 1 Oct 2026 11:27:22 +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=1790854044; cv=none; b=KcVva5L5QxNSj/VyUDKDl/nxXyocoxE3aIspzobCK2Gb0t1VpZAocRaBL+JyIaY6SNiah4VzDSe9W1HvoKmEga/Mg2+PrUvinGEPG5zq8OPGy27IV1CdffXrpFSBvMzEaXaD2dlHMp4cVR5EtO/ZFmRvHUNF0p9Fgn6iuvAPcu0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790854044; c=relaxed/simple; bh=d4OGQEeuxvHcje48FktNETn8iSb3Mzvo3MoqCA2atvk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=BAD6WkH50/+Pe2KRQNYHjmiMO0ytW7+RwtP9xGMh6AxFdnqw+nVqvxdNN3e+18qz30RCSCgCrFJGK8Epxr15kD7PUfziAjDPG5M1Pfb4bCY+KTMksA97IhGY5jVMAJqw8KfUn4Oq1yh5paENWApuHTEEJcV/kze5Qp4vnfSDj8o= 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=kPLS+Sf3; 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="kPLS+Sf3" 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 69175Ur01086044; Thu, 1 Oct 2026 11:26:54 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=G+JMOx 3eyLZi5m7sHNbAvGBo5rXVbzWrPNE7O72wjsk=; b=kPLS+Sf3IiN6W+lyf2OLUX EihD1XfN4iAs5gKoXaJ0S3H1OKhrpS/VYYFFQ8V6sD1vU3UgYejrCvnDiJSV6asf uaayXo2UdwOIp/gvsgvZgKYALcuD97/fk+/yrvFUGHi2bgohnzWazdHF2UT05BVb nno5M71Pgg0jF8nzmpcqSksF03uPMGK/2QFRKEImKwNGTGmcaEjwCRCwtrPzywm7 woSOJQFxFNJmoDUcp/0P2B4+NOpCBfVGdHsM3iLjOfQ0lAn09Zsqin30Nz8bG+dL mIcJTlRcptf4j1kHwGaasynLcLRIHLS8BO/KlfWP9jJb6obJAi9EXSNbbicbvEOA == Received: from ppma22.wdc07v.mail.ibm.com (5c.69.3da9.ip4.static.sl-reverse.com [169.61.105.92]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 4gx5pthk1m-1 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Thu, 01 Oct 2026 11:26:53 +0000 (GMT) Received: from pps.filterd (ppma22.wdc07v.mail.ibm.com [127.0.0.1]) by ppma22.wdc07v.mail.ibm.com (8.18.1.11/8.18.1.11) with ESMTP id 6917Hqi5545802; Thu, 1 Oct 2026 11:26:53 GMT Received: from smtprelay07.fra02v.mail.ibm.com ([9.218.2.229]) by ppma22.wdc07v.mail.ibm.com (PPS) with ESMTPS id 4h0xcsdngv-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 01 Oct 2026 11:26:52 +0000 (GMT) Received: from smtpav05.fra02v.mail.ibm.com (smtpav05.fra02v.mail.ibm.com [10.20.54.104]) by smtprelay07.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 691BQmub49152486 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 1 Oct 2026 11:26:49 GMT Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E010E20043; Thu, 1 Oct 2026 11:26:48 +0000 (GMT) Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B329520040; Thu, 1 Oct 2026 11:26:45 +0000 (GMT) Received: from [9.124.216.115] (unknown [9.124.216.115]) by smtpav05.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 1 Oct 2026 11:26:45 +0000 (GMT) Message-ID: <9d83e196-4d6b-4be1-811c-eb72527d3cdd@linux.ibm.com> Date: Thu, 1 Oct 2026 16:56:44 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] KVM: PPC: BookE: Disable preemption before loading guest FP and Altivec To: Shrikanth Hegde , maddy@linux.ibm.com, linuxppc-dev@lists.ozlabs.org, chzigotzky@xenosoft.de Cc: mpe@ellerman.id.au, npiggin@gmail.com, christophe.leroy@csgroup.eu, linux-kernel@vger.kernel.org, msuchanek@suse.de, ritesh.list@gmail.com, harshpb@linux.ibm.com, gautam@linux.ibm.com, amachhiw@linux.ibm.com, venkat88@linux.ibm.com References: <20260928110411.844582-1-sshegde@linux.ibm.com> <20260928110411.844582-2-sshegde@linux.ibm.com> Content-Language: en-US From: Narayana Murty N In-Reply-To: <20260928110411.844582-2-sshegde@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-ORIG-GUID: Kne6Ru6fHKCy0JZNtiEBfpsyQsLbFApA X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDAxMDA0NCBTYWx0ZWRfX38BxkTVeQnXc 6Vl9D51e7Nu1f6D83yROyZbg5VKExqIogxPk7Ndj3CoY3uQiS6Qe1bobyxaXViUWVevb4vtQbWH uH7HZNB4PiuF1XEJRC0BnvvUp/TpkaT2T1fV4JAl26kgAgFzI9cX2niZIU+MNaWPsDvsH8ZCkdx TiRU43DNmGSqKQVzdtNaHuci2uu5g3r5vMKj6VPk9JKamH64ezR0dlgQACrJKT6+4k/1OLffI6N QRmsPrhOjFyFxVBXPHdVOW7id5MBx8Ilw6avocGq5Ih/a8pp7zYlVdzYwn6jU+t6c1XprHwCnpN m+XL2wKldgkRlaypZAZvrm26FFyWzNl9NTUudyLxQ687fhb9qU7VVMJ20/inuQPgbh4RJUboPpw 5JlIcJcUvbg5L+zDioNFLElHcBU+zaQB0+aNH9pGZBoQ3yU+NPS/SncY3kGpyVHtJHcg7d6E/aq 9Q321k9XSgtLhdUlEpg== X-Proofpoint-Spam-Info: AW1haW4tMjYxMDAxMDA0NCBTYWx0ZWRfX/2yrfWEng1un shyrDKrF7Coc7Qzo+K93NWZc48ETUCuhIAoToK8kptuBBrEqWhWSH/Lm0qvF2xUw8wlPKS/SMpB E30jHLVugjTMb4m5W1IRHI8UfLraxs8= X-Authority-Analysis: v=2.4 cv=EY5d0/mC c=1 sm=1 tr=0 ts=6abe437d cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=660iZSQnnn4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=sxMExUxU4yiBR1plgyEA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: 94ZXvcctEXV5iOGxujJlL6wkQSmQbPum 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=2026-10-01_03,2026-09-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 priorityscore=1501 suspectscore=0 adultscore=0 clxscore=1015 malwarescore=0 impostorscore=0 spamscore=0 lowpriorityscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2610010044 Hi Shrikanth, Thanks for the fixes. I had one question on patch 1. On 28/09/26 4:34 PM, Shrikanth Hegde wrote: > Christian reported that booting preemptible kernel on FSL Cyrus+ board > causes boot hang. > > The logs pointed that system was busy in printing below warning. > > WARNING: at .enable_kernel_fp+0x30/0x78, CPU#3: qemu-system-ppc/4884 > Modules linked in: > CPU: 3 UID: 1000 PID: 4884 Comm: qemu-system-ppc Not tainted 7.3.0-rc1-powerpc64-smp-preempt #1 PREEMPT > NIP [c000000000003338] .enable_kernel_fp+0x30/0x78 > LR [c00000000005de84] .kvmppc_load_guest_fp+0x30/0x80 > Call Trace: > [c000000085ca7700] [c00000000005de84] .kvmppc_load_guest_fp+0x30/0x80 > [c000000085ca7780] [c00000000005f2a0] .kvmppc_handle_exit+0x5bc/0x5cc > [c000000085ca7830] [c00000000006204c] .kvmppc_resume_host+0xb8/0x10c > > Which is... > > void enable_kernel_fp(void) > { > unsigned long cpumsr; > WARN_ON(preemptible()); > > And... > > Though irq's are hard disabled after kvmppc_prepare_to_enter, but > kvmppc_fix_ee_before_entry enables the softmask's IRQ state. > That causes the irqs_disabled to return false. > Hence leading to the warnings. > > Fix it by disabling the preemption using the preempt disable. > Note, it is calling noresched variant of preempt enable, since hard > irq are disabled. It is likely not a good idea to call schedule. > > Fixes: 3efc7da61f6c ("KVM: PPC: Book3E: Increase FPU laziness") > Reported-by: Christian Zigotzky > Closes: https://lore.kernel.org/all/33342fbf-eb7b-bde6-2c8c-254fe8bfb993@xenosoft.de/ > Signed-off-by: Shrikanth Hegde > --- > arch/powerpc/kvm/booke.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c > index 13ad4cf5fa71..5b9118eefe1d 100644 > --- a/arch/powerpc/kvm/booke.c > +++ b/arch/powerpc/kvm/booke.c > @@ -1404,10 +1404,17 @@ int kvmppc_handle_exit(struct kvm_vcpu *vcpu, unsigned int exit_nr) > if (s <= 0) > r = (s << 2) | RESUME_HOST | (r & RESUME_FLAG_NV); > else { > - /* interrupts now hard-disabled */ > + /* > + * kvmppc_fix_ee_before_entry() marks the software > + * IRQ state enabled while interrupts are still > + * hard-disabled. So disable preemption while loading > + * guest FP and Altivec. > + */ > kvmppc_fix_ee_before_entry(); > + preempt_disable(); > kvmppc_load_guest_fp(vcpu); > kvmppc_load_guest_altivec(vcpu); > + preempt_enable_no_resched(); Would it be simpler to move kvmppc_fix_ee_before_entry() after the FP/Altivec loads instead? The normal kvmppc_vcpu_run() entry path already loads the guest FP/Altivec state while interrupts are still disabled and calls kvmppc_fix_ee_before_entry() immediately before entering the guest. So could this path follow the same ordering: kvmppc_load_guest_fp(vcpu); kvmppc_load_guest_altivec(vcpu); kvmppc_fix_ee_before_entry(); That would avoid making the software IRQ state enabled before loading the guest FP/Altivec state, and also avoid the additional preempt_disable()/preempt_enable_no_resched() pair. Thanks, Narayana Murty. > } > } >