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Wed, 26 Nov 2025 08:47:07 +0000 (GMT) Date: Wed, 26 Nov 2025 09:47:04 +0100 From: Claudio Imbrenda To: Heiko Carstens Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, borntraeger@de.ibm.com, frankja@linux.ibm.com, nsg@linux.ibm.com, nrb@linux.ibm.com, seiden@linux.ibm.com, gra@linux.ibm.com, schlameuss@linux.ibm.com, svens@linux.ibm.com, agordeev@linux.ibm.com, gor@linux.ibm.com, david@redhat.com, gerald.schaefer@linux.ibm.com Subject: Re: [PATCH v5 21/23] KVM: S390: Remove PGSTE code from linux/s390 mm Message-ID: <20251126094704.184c4987@p-imbrenda> In-Reply-To: <20251126083818.10107A70-hca@linux.ibm.com> References: <20251124115554.27049-1-imbrenda@linux.ibm.com> <20251124115554.27049-22-imbrenda@linux.ibm.com> <20251125192412.7336A36-hca@linux.ibm.com> <20251126083818.10107A70-hca@linux.ibm.com> Organization: IBM X-Mailer: Claws Mail 4.3.1 (GTK 3.24.49; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-s390@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-Details-Enc: AW1haW4tMjUxMTIyMDAwMCBTYWx0ZWRfX1Z6MYE5jLt6r S3W/TkfzzXPtDhGc+QqT4xV4qqrtIz0qJmj8hVe0/Pdvve6emAB9sp9RpkDeIcbFRi6bW5QWbD0 x02LU69O93fJu9EftfEitXO0z1PYszEOZVcKcACBJDG+ZWmO8cAS8Z99XY0p6F0IFF90kSVPiYM 9oRsnZvzlmS6BS/C2i0TkpkMbM8ClYuBkEKIwp5qLdv/h4OlgSk8g8Ku8oEuO2+lvolQ5tAl6zN SuarLhr+K4lTNd7HVE6RnO3HUwMJBh/mCx/Mt9N+4XkVLN8EG1zzAYMzEAx8Wg4HBTPmyzjihDd CdHLhQEeF1RsThzkY3odFA9n9lYRobNbjETuAA3NyAT8sUplga+gBCnYyJl7p3k4fdiZzV0sEv3 UgnNFgnmikyy1BOaIURxdiNkTIuDaw== X-Authority-Analysis: v=2.4 cv=fJM0HJae c=1 sm=1 tr=0 ts=6926be92 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=kj9zAlcOel0A:10 a=6UeiqGixMTsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=NnlkKe5a_FjY2rWv0OIA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-GUID: jMgqjiBl3dYhPlmDhVEzUpjs_aVozzif X-Proofpoint-ORIG-GUID: jMgqjiBl3dYhPlmDhVEzUpjs_aVozzif X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-11-25_02,2025-11-25_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 phishscore=0 priorityscore=1501 impostorscore=0 lowpriorityscore=0 suspectscore=0 malwarescore=0 adultscore=0 bulkscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2511220000 On Wed, 26 Nov 2025 09:38:18 +0100 Heiko Carstens wrote: > On Tue, Nov 25, 2025 at 08:24:12PM +0100, Heiko Carstens wrote: > > On Mon, Nov 24, 2025 at 12:55:52PM +0100, Claudio Imbrenda wrote: > > > Remove the PGSTE config option. > > > Remove all code from linux/s390 mm that involves PGSTEs. > > > > > > Signed-off-by: Claudio Imbrenda > > > --- > > > arch/s390/Kconfig | 3 - > > > arch/s390/include/asm/mmu.h | 13 - > > > arch/s390/include/asm/page.h | 4 - > > > arch/s390/include/asm/pgalloc.h | 4 - > > > arch/s390/include/asm/pgtable.h | 121 +---- > > > arch/s390/kvm/dat.h | 1 + > > > arch/s390/mm/hugetlbpage.c | 24 - > > > arch/s390/mm/pgalloc.c | 24 - > > > arch/s390/mm/pgtable.c | 829 +------------------------------- > > > mm/khugepaged.c | 9 - > > > 10 files changed, 17 insertions(+), 1015 deletions(-) > > > > ... > > > > > pte_t ptep_modify_prot_start(struct vm_area_struct *vma, unsigned long addr, > > > pte_t *ptep) > > > { > > > + preempt_disable(); > > > + return ptep_flush_lazy(vma->vm_mm, addr, ptep, 1); > > > } > > > > > > void ptep_modify_prot_commit(struct vm_area_struct *vma, unsigned long addr, > > > pte_t *ptep, pte_t old_pte, pte_t pte) > > > { > ... > > > + set_pte(ptep, pte); > > > + preempt_enable(); > > > } > > > > Why did you add the preempt_disable()/preempt_enable() pair? > > This causes preempt_count overflows. > > > > See modify_prot_start_ptes() + modify_prot_commit_ptes()... > > Ah, I guess this is probably just a rebase error, which by accident > re-introduced the code which was removed with commit 57834ce5a6a4 > ("s390/mm: Prevent possible preempt_count overflow"). that would indeed explain where that code comes from... I'll fix it