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Tue, 19 May 2026 15:01:19 +0000 (GMT) Received: from p-imbrenda.ibmuc.com (unknown [9.111.4.60]) by smtpav03.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 19 May 2026 15:01:19 +0000 (GMT) From: Claudio Imbrenda To: linux-kernel@vger.kernel.org Cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org, borntraeger@de.ibm.com, frankja@linux.ibm.com, david@kernel.org, seiden@linux.ibm.com, nrb@linux.ibm.com, schlameuss@linux.ibm.com, gra@linux.ibm.com Subject: [PATCH v3 5/5] KVM: s390: Properly reset zero bit in PGSTE Date: Tue, 19 May 2026 17:01:14 +0200 Message-ID: <20260519150114.264309-6-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260519150114.264309-1-imbrenda@linux.ibm.com> References: <20260519150114.264309-1-imbrenda@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=ffCdDUQF c=1 sm=1 tr=0 ts=6a0c7b47 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VnNF1IyMAAAA:8 a=P9Cbi09riAs7zLUs0OgA:9 X-Proofpoint-ORIG-GUID: i2IOlo9PbEkCjJiw3HyI6rtS6TboBsm1 X-Proofpoint-GUID: i2IOlo9PbEkCjJiw3HyI6rtS6TboBsm1 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTE5MDE0NSBTYWx0ZWRfX5naYB3cp8ZXA vnMRgpKmJ3O1Vp/u4iRuizLv0vPO9MduVDIuLESoRLkFgPjBJ1SLEfdJwzqVdZvUxg2NN/tgMYn o6hmCwnzC9bLX3mPb1hhxm5eOWLtqYH5ujNVI7zz5npNWk7nM4pQrU8hQnHWXgd2PLOyKeprrdB /GpFJd+oB868e833m919TygulR3lvXtyMBc12Q1Dmd9K58CNakLh62OtSQv5qZ+GkUSrf76Pvur WOW6XYlzx7n1sYLZEzBKuBvrDh1K10SN7JOni8vFtoA7L4OW64wT45vFQZxMjpEeAPw3Zgnsvos 4HUoMjaW2e7ym/aJrG3woK9OA6YIyRg3L90VyivRNMRLe9QPdxZ7qJcx0Og6EqUYMtei7+MCFc7 l8TodYEPrgE6cU693rd1h8TJWQxV1p5m0z9hpC6OQbXX3+lzHOstOHXuvMwTzMpNneG2ZkGxyzb Ntbb+YA32nL135la9YQ== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-05-19_04,2026-05-18_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 spamscore=0 phishscore=0 suspectscore=0 adultscore=0 clxscore=1015 impostorscore=0 lowpriorityscore=0 bulkscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605130000 definitions=main-2605190145 In case of memory pressure, it's possible that a guest page gets freed and then almost immediately reused by the guest. If CMMA is enabled, _essa_clear_cbrl() will discard all pages that are either unused or zero. If a discarded page is reused before _essa_clear_cbrl() is called, and the pgste.zero bit is not cleared, the page will be discarded despite not being unused. When calling _gmap_ptep_xchg(), always clear the pgste.zero bit. This prevents the page from being accidentally discarded when not unused. Signed-off-by: Claudio Imbrenda Fixes: a2c17f9270cc ("KVM: s390: New gmap code") Reviewed-by: Steffen Eiden --- arch/s390/kvm/gmap.h | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/s390/kvm/gmap.h b/arch/s390/kvm/gmap.h index 6e51ec6066b4..742e42a31744 100644 --- a/arch/s390/kvm/gmap.h +++ b/arch/s390/kvm/gmap.h @@ -220,6 +220,7 @@ static inline union pgste _gmap_ptep_xchg(struct gmap *gmap, union pte *ptep, un } if (!ptep->s.d && newpte.s.d && !newpte.s.s) SetPageDirty(pfn_to_page(newpte.h.pfra)); + pgste.zero = 0; return __dat_ptep_xchg(ptep, pgste, newpte, gfn, gmap->asce, uses_skeys(gmap)); } -- 2.54.0