From: Vladimir Murzin <vladimir.murzin@arm.com>
To: Will Deacon <will@kernel.org>, linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
Ard Biesheuvel <ardb@kernel.org>,
Ada Couprie Diaz <ada.coupriediaz@arm.com>,
David Hildenbrand <david@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Mostafa Saleh <smostafa@google.com>,
Lorenzo Stoakes <ljs@kernel.org>,
Oliver Upton <oupton@kernel.org>,
Linus Walleij <linusw@kernel.org>, Marc Zyngier <maz@kernel.org>
Subject: Re: [PATCH 00/21] arm64: Move overflow sp into SP_EL1 and kernel sp into SP_EL0
Date: Wed, 9 Sep 2026 11:39:24 +0100 [thread overview]
Message-ID: <40954731-a235-4877-b615-7a3f66f1b039@arm.com> (raw)
In-Reply-To: <20260907164247.17223-1-will@kernel.org>
Hi Will,
On 9/7/26 17:42, Will Deacon wrote:
> Hi everyone,
>
> This series is a bit of a complicated juggling act that, on its own,
> doesn't achieve an awful lot. However, it lays the ground work for
> sizing the kernel stack at runtime, e.g. via a cmdline option or even
> potentially on a per-task basis and so I would like to work towards
> getting it merged independently.
>
> The series is based on v7.3-rc1 and structured as follows:
>
> * The first 9 patches move the 'current' task pointer from SP_EL0
> to TPIDRRO_EL0.
>
> * The following 8 patches point the newly-freed SP_EL0 at the overflow
> stack and switch to it explicitly when we detect a kernel stack
> overflow.
>
> * The final 4 patches turn everything on its head, so that the
> overflow stack and kernel stack are swapped, with the former now
> residing in SP_EL1 and the latter in SP_EL0.
>
> At the end of all that, when we take an exception from EL1, we are
> immediately transitioned to the overflow stack (now renamed "exception
> stack") and can push registers right away. This also means that using
> SPINTMASK to control NMI masking becomes a possibility, although
> speaking to Mark, Vladimir and Ada, they all seem to prefer ALLINT.
>
> Mostafa will soon post a follow-up series that allows the kernel stack
> size to be specified on the kernel cmdline, which we are hoping to use
> to configure an 8k stack size in Android. I will be talking more about
> all of this at LPC in the Memory Management MC:
>
> https://lpc.events/event/20/contributions/2419/
>
> Cheers,
>
> Will
>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: Ada Couprie Diaz <ada.coupriediaz@arm.com>
> Cc: David Hildenbrand <david@kernel.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Vladimir Murzin <vladimir.murzin@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Mostafa Saleh <smostafa@google.com>
> Cc: Lorenzo Stoakes <ljs@kernel.org>
> Cc: Oliver Upton <oupton@kernel.org>
> Cc: Linus Walleij <linusw@kernel.org>
> Cc: Marc Zyngier <maz@kernel.org>
>
I gave it a try and I observe splat:
Unable to handle kernel execute from non-executable memory at virtual address ffff000970e81148
Mem abort info:
ESR = 0x000000008600000f
EC = 0x21: IABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x0f: level 3 permission fault
swapper pgtable: 4k pages, 48-bit VAs, pgdp=000000008129f000
[ffff000970e81148] pgd=0000000000000000, p4d=18000009f1dff403, pud=18000009f1079403, pmd=18000009f0ef1403, pte=00e80009f0e81707
Internal error: Oops: 000000008600000f [#1] SMP
Modules linked in:
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 7.3.0-rc2-7fb054f87+ #3627 PREEMPT(lazy)
Hardware name: Generated (DT)
pstate: 1634023c9 (nZCv DAIF +ALLINT +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
pc : 0xffff000970e81148
lr : 0xffff000970e81148
sp : ffff000970e81150
x29: ffff800080f85fc0 x28: 0000000000000001 x27: 0000000000002000
x26: 0000000000000000 x25: 00000000000000c0 x24: 0000000040000023
x23: ffff800080c0e1d8 x22: 00000000000003c0 x21: ffff800080b58300
x20: cfa2800080b58300 x19: 00000000200003c0 x18: 0000000000000000
x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000028
x14: 0000000000000000 x13: ffff8000814f3ac0 x12: ffff8008efcac000
x11: b2000c3eb474d99d x10: 0000000000000008 x9 : 0000000000001000
x8 : ffff800080010800 x7 : 055001f2b5503510 x6 : 0000000001310000
x5 : 0000000000000000 x4 : 0000000000000000 x3 : ffff800081502d80
x2 : 0000000000000802 x1 : ffff000800106a70 x0 : 0000000000000001
Call trace:
0xffff000970e81148 (P)
Code: 00000000 00000000 00000000 00000000 (00000002)
---[ end trace 0000000000000000 ]---
Kernel panic - not syncing: Oops: Fatal exception
SMP: stopping secondary CPUs
Kernel Offset: disabled
CPU features: 0x0,00000000,034bfc7d,ff728b42,7ffce667
Memory Limit: none
---[ end Kernel panic - not syncing: Oops: Fatal exception ]---
I suspect it is related to power management, since it can be triggered
with the sleep command, though I haven't debugged it. I noticed that
Sashiko has reported issues related to suspend/resume, so if you
provide fixups for the relevant commits, I can give them another
try. Otherwise, I'll wait for v2 :)
Cheers
Vladimir
next prev parent reply other threads:[~2026-09-09 10:39 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-07 16:42 Will Deacon
2026-09-07 16:42 ` [PATCH 01/21] arm64: entry: Defer setting of TPIDRRO_EL0 until exit to userspace Will Deacon
2026-09-11 7:53 ` Jinjie Ruan
2026-09-07 16:42 ` [PATCH 02/21] arm64: entry: Only check for stack overflow on exceptions from EL1 Will Deacon
2026-09-07 16:42 ` [PATCH 03/21] arm64: stackprotector: Temporarily disable per-task stackprotector Will Deacon
2026-09-07 16:42 ` [PATCH 04/21] arm64: bpf: Add support for generating reads of TPIDRRO_EL0 Will Deacon
2026-09-07 16:42 ` [PATCH 05/21] KVM: arm64: Protect TPIDRRO_EL0 across guest entry/exit Will Deacon
2026-09-07 16:42 ` [PATCH 06/21] arm64: Store 'current' in TPIDRRO_EL0 instead of SP_EL0 Will Deacon
2026-09-08 13:19 ` David Laight
2026-09-11 12:57 ` Will Deacon
2026-09-07 16:42 ` [PATCH 07/21] selftests/bpf: arm64: Use TPIDRRO_EL0 instead of SP_EL0 for 'current' Will Deacon
2026-09-07 16:42 ` [PATCH 08/21] scripts/gdb: " Will Deacon
2026-09-07 16:42 ` [PATCH 09/21] arm64: stackprotector: Re-enable per-task stackprotector Will Deacon
2026-09-07 16:42 ` [PATCH 10/21] arm64: percpu: Specialise set_my_cpu_offset() for the primary CPU Will Deacon
2026-09-07 16:42 ` [PATCH 11/21] arm64: percpu: Annotate __kern_my_cpu_offset() as '__always_inline' Will Deacon
2026-09-07 16:42 ` [PATCH 12/21] KVM: arm64: Preserve handler/thread bit of EL1 mode in __finalise_el2() Will Deacon
2026-09-07 16:42 ` [PATCH 13/21] arm64: sdei: Guard most of asm/sdei.h with CONFIG_ARM_SDE_INTERFACE Will Deacon
2026-09-07 16:42 ` [PATCH 14/21] arm64: sdei: Support SDEI events from kernel handler and thread modes Will Deacon
2026-09-07 16:42 ` [PATCH 15/21] arm64: entry: Point SP_EL0 at the overflow stack Will Deacon
2026-09-07 16:42 ` [PATCH 16/21] arm64: entry: Implement EL1t exception handlers for " Will Deacon
2026-09-07 16:42 ` [PATCH 17/21] arm64: entry: Use SPSel to switch to " Will Deacon
2026-09-07 16:42 ` [PATCH 18/21] arm64: entry: Split up kernel_ventry macro into separate helper macros Will Deacon
2026-09-07 16:42 ` [PATCH 19/21] arm64: entry: The great stack switcheroo Will Deacon
2026-09-08 11:30 ` Will Deacon
2026-09-07 16:42 ` [PATCH 20/21] arm64: tracing: Advertise a mode of EL1t in synthetic kernel regs Will Deacon
2026-09-07 16:42 ` [PATCH 21/21] arm64: Rename 'overflow_stack' and OVERFLOW_STACK_SIZE Will Deacon
2026-09-09 10:39 ` Vladimir Murzin [this message]
2026-09-09 11:29 ` [PATCH 00/21] arm64: Move overflow sp into SP_EL1 and kernel sp into SP_EL0 Will Deacon
2026-09-10 13:49 ` Vladimir Murzin
2026-09-11 12:57 ` Will Deacon
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