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Tue, 15 Sep 2026 14:43:08 +0000 (GMT) Received: from tuxmaker.boeblingen.de.ibm.com (unknown [9.87.85.9]) by smtpav05.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 15 Sep 2026 14:43:07 +0000 (GMT) From: Heiko Carstens To: Christian Borntraeger , Janosch Frank , Claudio Imbrenda , David Hildenbrand Cc: Vasily Gorbik , Sven Schnelle , Alexander Gordeev , kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] s390/uv: Rework page allocation for guest variable storage area Date: Tue, 15 Sep 2026 16:43:07 +0200 Message-ID: <20260915144307.2367089-1-hca@linux.ibm.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTE1MDIxMiBTYWx0ZWRfXzWs64YC4UIW9 22fRDHYZINLzhlrB4u6sIdUGB0UKSYycRj39mkRdjFA7lDSVzz+er1GlfvRg1W3yHyXSAkes95s VWwEQrTqjnPbnmbqIt1qyYx7AB8WojuiI+Z4+SqI8J+o2yvRxTob+WNza3ctXz+FgncEd3HfQkf L3YPfLJCO2aY4yE9WtRzacRyhH7W7ptSXLx0QC5mwWzT8XrOKmkDTIWSktmaYPQq1BJHbDbBPgQ m/4W7a6alUccnTGBMqO0Su+G0gqPwrANZRGpdDseotIcJhIp+MqY+ofDw4q54p6Dfrur4X7Bo94 pSDdPAT7YqN5fHCdrbF7uRB03223tmLBFeXvYBSTHAJaZLHVZuMVe3zAVpf/bP8WK+xVlOgn3md PpmeXQxyZexOLjeH2JwE38aLkLtEoVgFjW2LDDU2RtZfb59vT5DEPUu7S8JCzLjviVBD/ZlFKIu yMLOdpCQINyO4dPgu2Q== X-Proofpoint-GUID: LDqERbknEr98WpgudRfzRgxDf3EuklJQ X-Authority-Analysis: v=2.4 cv=DobDa2/+ c=1 sm=1 tr=0 ts=6aa95981 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=a2nUC81R4oW2uoHz82gA:9 X-Proofpoint-ORIG-GUID: LDqERbknEr98WpgudRfzRgxDf3EuklJQ X-Proofpoint-Spam-Info: AW1haW4tMjYwOTE1MDIxMiBTYWx0ZWRfX5PRnlRAm3ug0 JBEd2iY3SJIv2EBot1PYYmgXJ3EI+oBnQiPFk5yafH1Hl9f3ANY9hL+mcQUWhdKv0K5CDMt/i/m 3wjuVMy/HF7baiveNRd2cbLpYjHtg/0= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-09-15_04,2026-09-14_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 malwarescore=0 priorityscore=1501 suspectscore=0 impostorscore=0 spamscore=0 clxscore=1015 adultscore=0 bulkscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609150212 Alexander Gordeev reported that the allocation of pages of the guest variable storage area via the uv_alloc_range_cb() callback of apply_to_page_range() will cause problems as soon as s390 fully supports lazy mmu mode. Problem is that uv_alloc_range_cb() allocates pages with GFP_KERNEL while preemption would be disabled. This would result in reports like this: BUG: sleeping function called from invalid context at ./include/linux/sched/mm.h:322 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 6092, name: qemu-kvm preempt_count: 1, expected: 0 ... Call Trace: dump_stack_lvl+0xae/0x108 __might_resched+0x1de/0x2f0 prepare_alloc_pages+0x1ba/0x220 __alloc_frozen_pages_noprof+0xc6/0x390 alloc_pages_mpol+0xe6/0x220 alloc_frozen_pages_noprof+0x5c/0x80 alloc_pages_noprof+0x22/0x80 uv_alloc_range_cb+0x30/0x300 apply_to_pte_range+0x11a/0x3b0 apply_to_pmd_range+0x13a/0x250 __apply_to_page_range+0x232/0x4d0 apply_to_page_range+0x28/0x40 uv_alloc_stor_var+0x5e/0x90 kvm_s390_pv_alloc_vm+0x118/0x1e0 [kvm] kvm_s390_pv_init_vm+0x84/0x2e0 [kvm] kvm_s390_handle_pv+0x502/0xf70 [kvm] kvm_arch_vm_ioctl+0x234/0xdd0 [kvm] kvm_vm_ioctl+0x33a/0x890 [kvm] __s390x_sys_ioctl+0xfa/0x130 __do_syscall+0x1fc/0x700 system_call+0x72/0x90 Preallocate the pages and make use of vm_area_map_pages() to address this potential future bug. Reported-by: Alexander Gordeev Closes: https://lore.kernel.org/all/e9449c63-b8d2-4ed9-a184-7dcab3e8dfce-agordeev@linux.ibm.com Signed-off-by: Heiko Carstens --- Notes: This is untested, and only based on the report from Alexander. arch/s390/kernel/uv.c | 41 +++++++++++++++++++++++------------------ 1 file changed, 23 insertions(+), 18 deletions(-) diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c index dc14ebc0105b..3a01fc69cc3a 100644 --- a/arch/s390/kernel/uv.c +++ b/arch/s390/kernel/uv.c @@ -16,6 +16,7 @@ #include #include #include +#include #include #include #include @@ -242,34 +243,38 @@ void uv_free_stor_var(void *stor_var) } EXPORT_SYMBOL_FOR_MODULES(uv_free_stor_var, "kvm"); -static int uv_alloc_range_cb(pte_t *ptep, unsigned long addr, void *data) -{ - struct page *page; - pte_t pte; - - page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO); - if (!page) - return -ENOMEM; - pte = __pte(page_to_phys(page) | pgprot_val(PAGE_KERNEL)); - set_pte(ptep, pte); - return 0; -} - void *uv_alloc_stor_var(unsigned long size) { + unsigned long i, nr_pages, addr; struct vm_struct *area; - unsigned long addr; + struct page **pages; size = PAGE_ALIGN(size); + nr_pages = size >> PAGE_SHIFT; area = get_vm_area(size, VM_SPARSE); if (!area) return NULL; + pages = kvcalloc(nr_pages, sizeof(struct page *), GFP_KERNEL_ACCOUNT); + if (!pages) + goto free_area; + for (i = 0; i < nr_pages; i++) { + pages[i] = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO); + if (!pages[i]) + goto free_pages; + } addr = (unsigned long)area->addr; - if (apply_to_page_range(&init_mm, addr, size, uv_alloc_range_cb, NULL)) - goto out; + if (vm_area_map_pages(area, addr, addr + size, pages)) + goto free_pages; + kvfree(pages); return area->addr; -out: - uv_free_stor_var(area->addr); +free_pages: + for (i = 0; i < nr_pages; i++) { + if (pages[i]) + __free_page(pages[i]); + } + kvfree(pages); +free_area: + free_vm_area(area); return NULL; } EXPORT_SYMBOL_FOR_MODULES(uv_alloc_stor_var, "kvm"); -- 2.53.0