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Mon, 3 Aug 2026 14:54:49 +0000 (GMT) Date: Mon, 3 Aug 2026 16:54:46 +0200 From: Claudio Imbrenda To: Janosch Frank Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-s390@vger.kernel.org, borntraeger@de.ibm.com, david@kernel.org, seiden@linux.ibm.com, nrb@linux.ibm.com, schlameuss@linux.ibm.com, gra@linux.ibm.com Subject: Re: [PATCH v8 03/13] KVM: s390: Fix kvm_s390_vcpu_unsetup_cmma() Message-ID: <20260803165446.6d053a29@p-imbrenda> In-Reply-To: References: <20260803124040.126471-1-imbrenda@linux.ibm.com> <20260803124040.126471-4-imbrenda@linux.ibm.com> Organization: IBM X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Info: AW1haW4tMjYwODAzMDEzMyBTYWx0ZWRfX/7Q8rzQhwopC u3fJ8dGcpes37jRPeLSaS8LtbYtrhlZAbfBS67cXG6RLHTh79Sg5QT3iwcuIXJYf7kDmiK2V4/C K7ckIQR3VV1LLESEHKLIb00260C18SA= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODAzMDEzMyBTYWx0ZWRfX9OLWD0TDxPVm g6NjSJWuOr8+xI534wy7iq55wFtdRqvl1vcFaFQ447KrbBZ9hfCAglpEMx1LFvq6wgYmxCYZD3n 3XHnI1yz5wAC6UyihUscRj9yjK0kVqCRCiKhe7TX0YlxsNBfPUmwtknP/CVN4TonYW8QMNo1PCY S4F7HUCka0DQGhNFivzvMZuIpQO/D1h/C71vsAjv3nwnsZvb5fx576ciLIAcEFXrbA89aiIi7oO 2IkujylwD96SEid9HUxFDZotbwAL/qBGPhxhmpXuJMefZRVVl6YtOqi0dyqpCZeYm1pJ5044MQ9 Fcz3k3IxZye/Ms01G5fpyp6okIZxBhA+wtnmC0kNpRt2CFXMyO7fCvmcmEH1COzrtr1ZPDqYiJh wyekJIp68NTHMbCplTJ84jyUlL9/bYnUFTXzhvmMxe0ug+djtt3HoSTkNnFAIBKYSgB567kYVbR PTyzc9628c1ClYA8Wog== X-Authority-Analysis: v=2.4 cv=SI1ykuvH c=1 sm=1 tr=0 ts=6a70abc0 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=kj9zAlcOel0A:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VnNF1IyMAAAA:8 a=Q5H-Lj453KBsm_83YB8A:9 a=CjuIK1q_8ugA:10 X-Proofpoint-ORIG-GUID: krgsRFP6w2mNBLg35ftbpDRZegFlTGm5 X-Proofpoint-GUID: krgsRFP6w2mNBLg35ftbpDRZegFlTGm5 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=2026-08-03_03,2026-08-03_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 bulkscore=0 suspectscore=0 impostorscore=0 spamscore=0 phishscore=0 priorityscore=1501 lowpriorityscore=0 adultscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608030133 On Mon, 3 Aug 2026 16:30:21 +0200 Janosch Frank wrote: > On 8/3/26 14:40, Claudio Imbrenda wrote: > > In some cases kvm_s390_vcpu_unsetup_cmma() can be called with a 0 > > cbrlo; in such cases, if running with V != R, free_page() will attempt > > to free physical page 0. > > Secure guests without cmma in the unsecure guest? normal guests when the vCPU gets destroyed before it's fully initialized (i.e. something went wrong when creating the vCPU) > > > > > Fix by freeing cbrlo only if it's non-zero. > > > > Fixes: b31605c12f4e ("KVM: s390: make cmma usage conditionally") > > Fixes: 29b40f105ec8 ("KVM: s390: protvirt: Add initial vm and cpu lifecycle handling") > > Signed-off-by: Claudio Imbrenda > > --- > > arch/s390/kvm/kvm-s390.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c > > index 1b3290a5ad1a..9be27db0a21e 100644 > > --- a/arch/s390/kvm/kvm-s390.c > > +++ b/arch/s390/kvm/kvm-s390.c > > @@ -3678,7 +3678,8 @@ static void kvm_s390_vcpu_crypto_setup(struct kvm_vcpu *vcpu) > > > > void kvm_s390_vcpu_unsetup_cmma(struct kvm_vcpu *vcpu) > > { > > - free_page((unsigned long)phys_to_virt(vcpu->arch.sie_block->cbrlo)); > > + if (vcpu->arch.sie_block->cbrlo) > > + free_page((unsigned long)phys_to_virt(vcpu->arch.sie_block->cbrlo)); > > vcpu->arch.sie_block->cbrlo = 0; > > } > > > > This is fenced for destroy cpu, but not for the transition into secure > mode. Can we check "use_cmma" instead of cbrlo and then remove the > fencing in the cpu destroy path? > > If cmma is not set-up in vcpu_create, then we exit vcpu creation. > Maybe sprinkle in a warn on for !cbrlo