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Fri, 24 Jul 2026 08:17:25 +0000 (GMT) Received: from p-imbrenda (unknown [9.224.75.30]) by smtpav02.fra02v.mail.ibm.com (Postfix) with SMTP; Fri, 24 Jul 2026 08:17:25 +0000 (GMT) Date: Fri, 24 Jul 2026 10:17:22 +0200 From: Claudio Imbrenda To: Christian Borntraeger Cc: Heiko Carstens , Alexander Gordeev , Sven Schnelle , Vasily Gorbik , Janosch Frank , David Hildenbrand , linux-s390@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 5/8] s390/mm: Remove folio handling for kernel faults in do_secure_storage_access() Message-ID: <20260724101722.363655e5@p-imbrenda> In-Reply-To: References: <20260720085834.898025-1-hca@linux.ibm.com> <20260720085834.898025-6-hca@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-ORIG-GUID: qupa1iDYGK9lhvlWto5MfvPZqI0CLsfT X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzI0MDA3MyBTYWx0ZWRfX6KEt9X41m3bN QnQENmb2/CMNOkUZRioOI34vxD+IDZDAn7JsxQBhrd878Ju96h3OA+EFPjkJVMkoF4uTNKAUS8w 4yGUjEYsQ2ZPNXzec0Tj6y4VYqt4uM/RRIOP3+8fpQOi1wbQyuog1Evlsu2/CdBibWme2wXGT/y 1jH4t89/d3xEfD+gKRql18LGgoEBo37Fmp27wHNZiiSm6tpsmaTIOCnK12T1amAPjH5zQyLBHAS CF5jkCQ3wcDOGXDIbI3g1r1Fz/tbsE20re1yNOkFsIlZHLpaXtMe8yPq/KXA231vgILlm+q/y4s 2vrmSm+rsWbLHNnrIM0hOEITr6jNM70TWGxkB2ogNTAeJcStRRj19IkhT8/82U5zm12d/KcAH41 QO26Yz5ztKvSTnUAyrhaugGDYl/7UjecBaMGdp8sKuJIVxTCNAgCoObI/Po/Cc4dKP3qfvdnuLy uRTHKePGyFX+gDmAmzQ== X-Proofpoint-Spam-Info: AW1haW4tMjYwNzI0MDA3MyBTYWx0ZWRfXySChLbt9kEdD 2f9Ct0UNC2s3mlS50H84wZNLDd8c7922JPBqBQKjC55Ol/GY+bTonYCorEio3LXwRlFGJDhc3Ef ye6Qx+L0Slcd4KRZG+aVdFLnRnggdD0= X-Proofpoint-GUID: qupa1iDYGK9lhvlWto5MfvPZqI0CLsfT X-Authority-Analysis: v=2.4 cv=SM5ykuvH c=1 sm=1 tr=0 ts=6a631fa2 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=kj9zAlcOel0A:10 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VnNF1IyMAAAA:8 a=uVMGJkIZJPMhafez8PoA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-24_01,2026-07-22_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 lowpriorityscore=0 bulkscore=0 suspectscore=0 adultscore=0 spamscore=0 malwarescore=0 priorityscore=1501 phishscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607240073 On Mon, 20 Jul 2026 12:53:29 +0200 Christian Borntraeger wrote: > Am 20.07.26 um 10:58 schrieb Heiko Carstens: > > Remove folio handling for secure storage access exceptions that happen > > via the kernel mapping. Using folio_try_get() for exceptions via the > > kernel mapping is racy: for example such an exception may happen on one > > CPU, while a different CPU frees the corresponding page. Subsequently the > > page can be part of a folio of different size, before the faulting CPU > > executes folio_try_get(). This may lead to data corruption. > > > > As of now this scenario does not seem to be possible, however with the > > upcoming load_unaligned_zeropad() this is possible. > > > > As a side effect PG_arch_1 is not cleared anymore for such faults via the > > kernel mapping. However given that this bit is over-indicating it > > shouldn't matter. > > > > Tested-by: Christian Borntraeger > > Signed-off-by: Heiko Carstens > > Ideally Claudio should confirm that PG_arch_1 is over-indicating. PG_arch_1 is over-indicating. Acked-by: Claudio Imbrenda > > Reviewed-by: Christian Borntraeger > > > --- > > arch/s390/mm/fault.c | 8 +------- > > 1 file changed, 1 insertion(+), 7 deletions(-) > > > > diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c > > index e650cdfa2523..776549d55c94 100644 > > --- a/arch/s390/mm/fault.c > > +++ b/arch/s390/mm/fault.c > > @@ -440,13 +440,7 @@ void do_secure_storage_access(struct pt_regs *regs) > > if (is_kernel_fault(regs)) { > > if (is_vmalloc_addr((void *)addr)) > > return handle_fault_error_nolock(regs, 0); > > - folio = virt_to_folio((void *)addr); > > - if (unlikely(!folio_try_get(folio))) > > - return; > > - rc = uv_convert_from_secure(folio_to_phys(folio)); > > - if (!rc) > > - clear_bit(PG_arch_1, &folio->flags.f); > > - folio_put(folio); > > + rc = uv_convert_from_secure(__pa(addr)); > > /* > > * There are some valid fixup types for kernel > > * accesses to donated secure memory. zeropad is one >