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Mon, 15 Jun 2026 11:50:01 +0000 (GMT) Received: from osiris (unknown [9.111.80.197]) by smtpav06.fra02v.mail.ibm.com (Postfix) with ESMTPS; Mon, 15 Jun 2026 11:50:01 +0000 (GMT) Date: Mon, 15 Jun 2026 13:50:00 +0200 From: Heiko Carstens To: Claudio Imbrenda Cc: linux-kernel@vger.kernel.org, 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, gerald.schaefer@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, svens@linux.ibm.com Subject: Re: [PATCH v2 1/1] s390/mm: Fix handling of _PAGE_UNUSED pte bit Message-ID: <20260615115000.31370Ef1-hca@linux.ibm.com> References: <20260615091741.76724-1-imbrenda@linux.ibm.com> <20260615091741.76724-2-imbrenda@linux.ibm.com> <20260615094300.31370D7a-hca@linux.ibm.com> <20260615123103.118af04a@p-imbrenda> 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-Disposition: inline In-Reply-To: <20260615123103.118af04a@p-imbrenda> X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Info: AW1haW4tMjYwNjE1MDEyNSBTYWx0ZWRfXz4L9zh2iFVRL wMByOKkFR1sy/cLD2r7atGOoDTyygmf7Ldwbtp9Ldqr3PlPuHbR9dTLompITD3tq6JgPZW8Q3xq 18yjTszRcpue8vMvE+UkiKInTcu50Z8= X-Proofpoint-GUID: 0ep69pgvSHeSdQaNH-B-5KWRQ8hdtpMi X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjE1MDEyNSBTYWx0ZWRfX5zX7bHWlzDDd W5ET+OOc0lrMnESKm6ZUBbWRm5vgAHiqYtdRtlpnMwDn0nWB1MRN9VY06Za1yn3jnaiTmIRG0xp TgjPZ1MmuxyXNfT8YBFeYicdY5Zr64UpeINgJSVV46RcvT6PzbvLxsGBLfoRCy+eyycPITm/7uV joxrPlNPObwp0v7mflue1JsxhFMKKKVN6MBYgAyMRpU7jgOnV85FXOl2duZ/xIjOS2+DySp8m4b sCMBC0KiKGKSgRyvwxpnRY00AAIeZSMvMtV2HAueKuzJo5yVPeTH7DqqLcR6h1/k49h9dJKFasZ 1WQDp9cotB13oGYN4HGgsE3ZsAwey24cFCmUqGlQQBAiY/GzuQ2rl7BHBmSCuXDH+/xuBWSAsH+ ZODr2AaHa/IayKa7tl1pEARmvnR421mm1P4V+oePUYWEjqap+w1U+3x0ZTKHHndqMQSidsSKMQP tOEyPEcg8I9/GSaCW0w== X-Proofpoint-ORIG-GUID: 0ep69pgvSHeSdQaNH-B-5KWRQ8hdtpMi X-Authority-Analysis: v=2.4 cv=Dd0nbPtW c=1 sm=1 tr=0 ts=6a2fe6ef cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=kj9zAlcOel0A:10 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VnNF1IyMAAAA:8 a=eJsfp5Q3Ls_MATEj3MsA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-15_03,2026-06-15_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 clxscore=1015 priorityscore=1501 impostorscore=0 lowpriorityscore=0 adultscore=0 suspectscore=0 phishscore=0 spamscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606040000 definitions=main-2606150125 On Mon, Jun 15, 2026 at 12:31:03PM +0200, Claudio Imbrenda wrote: > On Mon, 15 Jun 2026 11:43:00 +0200 > Heiko Carstens wrote: > > [...] > > > > @@ -175,6 +179,8 @@ pte_t ptep_modify_prot_start(struct > vm_area_struct *vma, unsigned long addr, > > > void ptep_modify_prot_commit(struct vm_area_struct *vma, unsigned long addr, > > > pte_t *ptep, pte_t old_pte, pte_t pte) > > > { > > > + if (pte_present(pte)) > > > + pte = clear_pte_bit(pte, __pgprot(_PAGE_UNUSED)); > > > set_pte(ptep, pte); > > > > Can't we move the logic from set_ptes() to set_pte() instead? The above > > set_pte() is also used for things that are not ptes, and in those cases > we probably don't want to touch that bit, although technically it is > currently unused for present large pmds and puds. I can only see huge_pte_clear() for this. If that's the only user I'd rather add a BUG_ON() there instead of starting to sprinkle the logic around. This _will_ break sooner or later.