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Mon, 27 Jul 2026 10:37:11 +0000 (GMT) Received: from localhost (unknown [9.87.133.185]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTPS; Mon, 27 Jul 2026 10:37:11 +0000 (GMT) Date: Mon, 27 Jul 2026 12:37:09 +0200 From: Vasily Gorbik To: Heiko Carstens Cc: Alexander Gordeev , Sven Schnelle , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , David Hildenbrand , linux-s390@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 0/8] s390: Reintroduce support for DCACHE_WORD_ACCESS Message-ID: References: <20260720085834.898025-1-hca@linux.ibm.com> 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=utf-8 Content-Disposition: inline In-Reply-To: <20260720085834.898025-1-hca@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: gA-c4IJzNdW8gFwDMfDJgse5MrdaonoS X-Proofpoint-Spam-Info: AW1haW4tMjYwNzI3MDEwMCBTYWx0ZWRfX0N+8N4oZBd8p 897e6WIDgO6yTJ04fFk6sCjNdehPQRxsCzgb7NXBZOVPZFclDr20W4Z5eTXdxW8+HX8tX+d9coJ QEEukpL9XkPfPDyU9TdtoiZLZtyeFCQ= X-Authority-Analysis: v=2.4 cv=E/z9Y6dl c=1 sm=1 tr=0 ts=6a6734dc cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=x38aFKVj8ROUqmG2MhkA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzI3MDEwMCBTYWx0ZWRfX/4LJKjJo8CYq n9RI6Zi9s1eVDw7kW2HpeOc4/yQICt+uAQuz1RIjzii90hw/EuBeLTRMQXwOPD1YEt0agFv9jsq 4avrM1DBy6Lnb6nDNlvMumqztHE6QnUghQ/wYjkp5rQlKJ4fpaOA5vRB9PhAC9GoRBN2ppRWVFM JsmkUUZ2LVy02yhSd1YyelWKB5uw3+OP3myKnYcA2klQzBfi+Dp9qj46AKe/E2SdHafjqh2FYo9 UNwjDnGb/QIbt/mpNwFdOb3kdzqLKsC35lKxrU4bi5ieLM5AWI1K785alTIChATqLyQQrRxlwiL K1HXrz/ymJawkXinj+LIH9Y2LxQmuKdN4GnsdkICh+lOPWCyHPs4XZ8h8DtaspBSCKv7OWPylgT h/+Q3ubFZ+8e8z+8w+GiSzpWXmLdrU1iJPXZY1zJF7Rqvy/YAHxJ4bU/g9XEqZyDiaXiBTjiQb4 rckhVwtdcZlJdmrYjsw== X-Proofpoint-GUID: gA-c4IJzNdW8gFwDMfDJgse5MrdaonoS 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=2026-07-27_03,2026-07-24_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 priorityscore=1501 spamscore=0 clxscore=1011 phishscore=0 lowpriorityscore=0 bulkscore=0 malwarescore=0 impostorscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607270100 On Mon, Jul 20, 2026 at 10:58:26AM +0200, Heiko Carstens wrote: > v4: > - Add two more cleanup patches based on Sashiko feedback, however I > don't consider them as bug fixes. This is more cosmetics: > - Use handle_fault_error() in do_secure_storage_access() > - Use goto statement in do_secure_storage_access() > > v3: > - Fix two more pre-existing bugs reported by Sashiko > - Add Christian's Tested-by tag to four of the six patches > > v2: > - Explicitely PAGE_ALIGN size in uv_alloc_stor_var() [Sashiko] > - Document that lazy PTE update / TLB flushing is intended [Sashiko] > > v1: > Support for DCACHE_WORD_ACCESS was recently removed [1] since it caused > problems with the incomplete handling of secure storage access > exceptions. It looked like fixing the exception handler would be a larger > effort; therefore support for DCACHE_WORD_ACCESS was removed as a work > around. > > Address the potential problems that exist with secure storage access > exceptions and add support for DCACHE_WORD_ACCESS again. > > In particular address the following problems: > > - Reading the guest variable storage area via the /proc/kcore interface > results in short reads. Address this by using a VM_SPARSE area for the > guest variable storage area. VM_SPARSE areas will be handled like > memory holes (zeros will be read). > > - Fix handling of secure storage access exceptions in vmalloc area. > > - Remove folio handling for secure storage access exceptions to avoid > potential data corruption. > > [1] 37540b8c287f ("s390: Revert support for DCACHE_WORD_ACCESS") > > Heiko Carstens (8): > KVM: s390: pv: Use VM_SPARSE area for guest variable storage area > s390/mm: Add missing mm check to do_secure_storage_access() > s390/mm: Use lock_mm_and_find_vma() in do_secure_storage_access() > s390/mm: Fix handling of vmalloc area in do_secure_storage_access() > s390/mm: Remove folio handling for kernel faults in do_secure_storage_access() > s390/mm: Use handle_fault_error() in do_secure_storage_access() > s390/mm: Use goto statement in do_secure_storage_access() > s390: Add support for DCACHE_WORD_ACCESS (again) > > arch/s390/Kconfig | 1 + > arch/s390/include/asm/asm-extable.h | 4 ++ > arch/s390/include/asm/uv.h | 2 + > arch/s390/include/asm/word-at-a-time.h | 22 +++++++++ > arch/s390/kernel/uv.c | 65 ++++++++++++++++++++++++++ > arch/s390/kvm/pv.c | 6 +-- > arch/s390/mm/extable.c | 18 +++++++ > arch/s390/mm/fault.c | 35 ++++++-------- > 8 files changed, 128 insertions(+), 25 deletions(-) Applied, thank you!