kernel/arch/s390, branch linux-rolling-lts

s390/xor: Fix xor_xc_5() inline assembly

2026-03-19T15:08:39Z

commit 5f25805303e201f3afaff0a90f7c7ce257468704 upstream. xor_xc_5() contains a larl 1,2f that is not used by the asm and is not declared as a clobber. This can corrupt a compiler-allocated value in %r1 and lead to miscompilation. Remove the instruction. Fixes: 745600ed6965 ("s390/lib: Use exrl instead of ex in xor functions") Cc: stable@vger.kernel.org Reviewed-by: Juergen Christ Reviewed-by: Heiko Carstens Reviewed-by: Sven Schnelle Signed-off-by: Vasily Gorbik Signed-off-by: Greg Kroah-Hartman

s390/xor: Fix xor_xc_2() inline assembly constraints

2026-03-19T15:08:39Z

commit f775276edc0c505dc0f782773796c189f31a1123 upstream. The inline assembly constraints for xor_xc_2() are incorrect. "bytes", "p1", and "p2" are input operands, while all three of them are modified within the inline assembly. Given that the function consists only of this inline assembly it seems unlikely that this may cause any problems, however fix this in any case. Fixes: 2cfc5f9ce7f5 ("s390/xor: optimized xor routing using the XC instruction") Cc: stable@vger.kernel.org Signed-off-by: Heiko Carstens Reviewed-by: Vasily Gorbik Link: https://lore.kernel.org/r/20260302133500.1560531-2-hca@linux.ibm.com Signed-off-by: Vasily Gorbik Signed-off-by: Greg Kroah-Hartman

s390/stackleak: Fix __stackleak_poison() inline assembly constraint

2026-03-19T15:08:38Z

commit 674c5ff0f440a051ebf299d29a4c013133d81a65 upstream. The __stackleak_poison() inline assembly comes with a "count" operand where the "d" constraint is used. "count" is used with the exrl instruction and "d" means that the compiler may allocate any register from 0 to 15. If the compiler would allocate register 0 then the exrl instruction would not or the value of "count" into the executed instruction - resulting in a stackframe which is only partially poisoned. Use the correct "a" constraint, which excludes register 0 from register allocation. Fixes: 2a405f6bb3a5 ("s390/stackleak: provide fast __stackleak_poison() implementation") Cc: stable@vger.kernel.org Signed-off-by: Heiko Carstens Reviewed-by: Vasily Gorbik Link: https://lore.kernel.org/r/20260302133500.1560531-4-hca@linux.ibm.com Signed-off-by: Vasily Gorbik Signed-off-by: Greg Kroah-Hartman

s390/pfault: Fix virtual vs physical address confusion

2026-03-19T15:08:34Z

commit d879ac6756b662a085a743e76023c768c3241579 upstream. When Linux is running as guest, runs a user space process and the user space process accesses a page that the host has paged out, the guest gets a pfault interrupt and schedules a different process. Without this mechanism the host would have to suspend the whole virtual CPU until the page has been paged in. To setup the pfault interrupt the real address of parameter list should be passed to DIAGNOSE 0x258, but a virtual address is passed instead. That has a performance impact, since the pfault setup never succeeds, the interrupt is never delivered to a guest and the whole virtual CPU is suspended as result. Cc: stable@vger.kernel.org Fixes: c98d2ecae08f ("s390/mm: Uncouple physical vs virtual address spaces") Reported-by: Claudio Imbrenda Reviewed-by: Heiko Carstens Signed-off-by: Alexander Gordeev Signed-off-by: Vasily Gorbik Signed-off-by: Greg Kroah-Hartman

kbuild: Split .modinfo out from ELF_DETAILS

2026-03-12T11:09:44Z

commit 8678591b47469fe16357234efef9b260317b8be4 upstream. Commit 3e86e4d74c04 ("kbuild: keep .modinfo section in vmlinux.unstripped") added .modinfo to ELF_DETAILS while removing it from COMMON_DISCARDS, as it was needed in vmlinux.unstripped and ELF_DETAILS was present in all architecture specific vmlinux linker scripts. While this shuffle is fine for vmlinux, ELF_DETAILS and COMMON_DISCARDS may be used by other linker scripts, such as the s390 and x86 compressed boot images, which may not expect to have a .modinfo section. In certain circumstances, this could result in a bootloader failing to load the compressed kernel [1]. Commit ddc6cbef3ef1 ("s390/boot/vmlinux.lds.S: Ensure bzImage ends with SecureBoot trailer") recently addressed this for the s390 bzImage but the same bug remains for arm, parisc, and x86. The presence of .modinfo in the x86 bzImage was the root cause of the issue worked around with commit d50f21091358 ("kbuild: align modinfo section for Secureboot Authenticode EDK2 compat"). misc.c in arch/x86/boot/compressed includes lib/decompress_unzstd.c, which in turn includes lib/xxhash.c and its MODULE_LICENSE / MODULE_DESCRIPTION macros due to the STATIC definition. Split .modinfo out from ELF_DETAILS into its own macro and handle it in all vmlinux linker scripts. Discard .modinfo in the places where it was previously being discarded from being in COMMON_DISCARDS, as it has never been necessary in those uses. Cc: stable@vger.kernel.org Fixes: 3e86e4d74c04 ("kbuild: keep .modinfo section in vmlinux.unstripped") Reported-by: Ed W Closes: https://lore.kernel.org/587f25e0-a80e-46a5-9f01-87cb40cfa377@wildgooses.com/ [1] Tested-by: Ed W # x86_64 Link: https://patch.msgid.link/20260225-separate-modinfo-from-elf-details-v1-1-387ced6baf4b@kernel.org Signed-off-by: Nathan Chancellor Signed-off-by: Greg Kroah-Hartman

s390/vtime: Fix virtual timer forwarding

2026-03-12T11:09:17Z

[ Upstream commit dbc0fb35679ed5d0adecf7d02137ac2c77244b3b ] Since delayed accounting of system time [1] the virtual timer is forwarded by do_account_vtime() but also vtime_account_kernel(), vtime_account_softirq(), and vtime_account_hardirq(). This leads to double accounting of system, guest, softirq, and hardirq time. Remove accounting from the vtime_account*() family to restore old behavior. There is only one user of the vtimer interface, which might explain why nobody noticed this so far. Fixes: b7394a5f4ce9 ("sched/cputime, s390: Implement delayed accounting of system time") [1] Reviewed-by: Sven Schnelle Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik Signed-off-by: Sasha Levin

s390/idle: Fix cpu idle exit cpu time accounting

2026-03-12T11:09:17Z

[ Upstream commit 0d785e2c324c90662baa4fe07a0d02233ff92824 ] With the conversion to generic entry [1] cpu idle exit cpu time accounting was converted from assembly to C. This introduced an reversed order of cpu time accounting. On cpu idle exit the current accounting happens with the following call chain: -> do_io_irq()/do_ext_irq() -> irq_enter_rcu() -> account_hardirq_enter() -> vtime_account_irq() -> vtime_account_kernel() vtime_account_kernel() accounts the passed cpu time since last_update_timer as system time, and updates last_update_timer to the current cpu timer value. However the subsequent call of -> account_idle_time_irq() will incorrectly subtract passed cpu time from timer_idle_enter to the updated last_update_timer value from system_timer. Then last_update_timer is updated to a sys_enter_timer, which means that last_update_timer goes back in time. Subsequently account_hardirq_exit() will account too much cpu time as hardirq time. The sum of all accounted cpu times is still correct, however some cpu time which was previously accounted as system time is now accounted as hardirq time, plus there is the oddity that last_update_timer goes back in time. Restore previous behavior by extracting cpu time accounting code from account_idle_time_irq() into a new update_timer_idle() function and call it before irq_enter_rcu(). Fixes: 56e62a737028 ("s390: convert to generic entry") [1] Reviewed-by: Sven Schnelle Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik Signed-off-by: Sasha Levin

s390/pci: Handle futile config accesses of disabled devices directly

2026-03-04T12:21:07Z

[ Upstream commit 84d875e69818bed600edccb09be4a64b84a34a54 ] On s390 PCI busses and slots with multiple functions may have holes because PCI functions are passed-through by the hypervisor on a per function basis and some functions may be in standby or reserved. This fact is indicated by returning true from the hypervisor_isolated_pci_functions() helper and triggers common code to scan all possible devfn values. Via pci_scan_single_device() this in turn causes config reads for the device and vendor IDs, even for PCI functions which are in standby and thereofore disabled. So far these futile config reads, as well as potentially writes, which can never succeed were handled by the PCI load/store instructions themselves. This works as the platform just returns an error for a disabled and thus not usable function handle. It does cause spamming of error logs and additional overhead though. Instead check if the used function handle is enabled in zpci_cfg_load() and zpci_cfg_write() and if not enable directly return -ENODEV. Also refactor zpci_cfg_load() and zpci_cfg_store() slightly to accommodate the new logic while meeting modern kernel style guidelines. Cc: stable@vger.kernel.org Fixes: a50297cf8235 ("s390/pci: separate zbus creation from scanning") Signed-off-by: Niklas Schnelle Reviewed-by: Benjamin Block Reviewed-by: Farhan Ali Signed-off-by: Heiko Carstens Signed-off-by: Sasha Levin

s390/perf: Disable register readout on sampling events

2026-03-04T12:19:37Z

[ Upstream commit b2c04fc1239062b39ddfdd8731ee1a10810dfb74 ] Running commands # ./perf record -IR0,R1 -a sleep 1 extracts and displays register value of general purpose register r1 and r0. However the value displayed of any register is random and does not reflect the register value recorded at the time of the sample interrupt. The sampling device driver on s390 creates a very large buffer for the hardware to store the samples. Only when that large buffer gets full an interrupt is generated and many hundreds of sample entries are processed and copied to the kernel ring buffer and eventually get copied to the perf tool. It is during the copy to the kernel ring buffer that each sample is processed (on s390) and at that time the register values are extracted. This is not the original goal, the register values should be read when the samples are created not when the samples are copied to the kernel ring buffer. Prevent this event from being installed in the first place and return -EOPNOTSUPP. This is already the case for PERF_SAMPLE_REGS_USER. Signed-off-by: Thomas Richter Reviewed-by: Jan Polensky Signed-off-by: Heiko Carstens Signed-off-by: Sasha Levin

s390/purgatory: Add -Wno-default-const-init-unsafe to KBUILD_CFLAGS

2026-03-04T12:19:33Z

[ Upstream commit b4780fe4ddf04b51127a33d705f4a2e224df00fa ] Add -Wno-default-const-init-unsafe to purgatory KBUILD_CFLAGS, similar to scripts/Makefile.extrawarn, since clang generates warnings for the dummy variable in typecheck(): CC arch/s390/purgatory/purgatory.o arch/s390/include/asm/ptrace.h:221:9: warning: default initialization of an object of type 'typeof (regs->psw)' (aka 'const psw_t') leaves the object uninitialized [-Wdefault-const-init-var-unsafe] 221 | return psw_bits(regs->psw).pstate; | ^ arch/s390/include/asm/ptrace.h:98:2: note: expanded from macro 'psw_bits' 98 | typecheck(psw_t, __psw); \ | ^ include/linux/typecheck.h:11:12: note: expanded from macro 'typecheck' 11 | typeof(x) __dummy2; \ | ^ Signed-off-by: Heiko Carstens Signed-off-by: Sasha Levin