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Wed, 26 Feb 2025 17:26:12 +0000 (GMT) Date: Wed, 26 Feb 2025 18:26:10 +0100 From: Claudio Imbrenda To: David Hildenbrand Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, frankja@linux.ibm.com, borntraeger@de.ibm.com, nrb@linux.ibm.com, seiden@linux.ibm.com, nsg@linux.ibm.com, schlameuss@linux.ibm.com, hca@linux.ibm.com Subject: Re: [PATCH v2 1/1] KVM: s390: pv: fix race when making a page secure Message-ID: <20250226182610.7f5313ca@p-imbrenda> In-Reply-To: References: <20250226123725.247578-1-imbrenda@linux.ibm.com> <20250226123725.247578-2-imbrenda@linux.ibm.com> <0dfeabca-5c41-4555-a43b-341a54096036@redhat.com> <20250226175833.16a7a970@p-imbrenda> Organization: IBM X-Mailer: Claws Mail 4.3.0 (GTK 3.24.43; 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-GUID: 5OyKm02NnWNxEvgMIiXTeCrhjixIc5mN X-Proofpoint-ORIG-GUID: 5OyKm02NnWNxEvgMIiXTeCrhjixIc5mN X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-02-26_04,2025-02-26_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 suspectscore=0 mlxlogscore=960 phishscore=0 adultscore=0 clxscore=1015 bulkscore=0 priorityscore=1501 mlxscore=0 spamscore=0 lowpriorityscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2502100000 definitions=main-2502260134 On Wed, 26 Feb 2025 18:01:04 +0100 David Hildenbrand wrote: > On 26.02.25 17:58, Claudio Imbrenda wrote: > > On Wed, 26 Feb 2025 16:05:11 +0100 > > David Hildenbrand wrote: > > > >>> +int make_hva_secure(struct mm_struct *mm, unsigned long hva, struct uv_cb_header *uvcb) > >>> +{ > >>> + struct folio *folio; > >>> + spinlock_t *ptelock; > >>> + pte_t *ptep; > >>> + int rc; > >>> + > >>> + ptep = get_locked_valid_pte(mm, hva, &ptelock); > >>> + if (!ptep) > >>> + return -ENXIO; > >> > >> You very likely need a pte_write() check we had there before, as you > >> might effectively modify page content by clearing the page. > > > > it's not really needed, but it doesn't hurt either, I'll add a check > > Can you elaborate why it is not needed? Would the HW enforce that > writability check already? as I have discovered the hard way while working on this v2, yes but as I said, it looks better with the check, so I'll add it