From: Will Deacon <will@kernel.org>
To: David Laight <david.laight.linux@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
Vladimir Murzin <vladimir.murzin@arm.com>,
Arnd Bergmann <arnd@arndb.de>,
Catalin Marinas <catalin.marinas@arm.com>,
Linus Walleij <linusw@kernel.org>,
linux-kernel@vger.kernel.org, Mostafa Saleh <smostafa@google.com>,
Marc Zyngier <maz@kernel.org>,
David Hildenbrand <david@kernel.org>,
Lorenzo Stoakes <ljs@kernel.org>,
Oliver Upton <oupton@kernel.org>,
Ard Biesheuvel <ardb@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 06/21] arm64: Store 'current' in TPIDRRO_EL0 instead of SP_EL0
Date: Fri, 11 Sep 2026 13:57:25 +0100 [thread overview]
Message-ID: <aqP6tdHf-3hnTLhf@willie-the-truck> (raw)
In-Reply-To: <20260908141950.37e9ed3d@pumpkin>
On Tue, Sep 08, 2026 at 02:19:50PM +0100, David Laight wrote:
> On Mon, 7 Sep 2026 17:42:31 +0100
> Will Deacon <will@kernel.org> wrote:
>
> > To make SP_EL0 available to point at the per-cpu kernel overflow stack,
> > we must relocate 'current' elsewhere. With TPIDRRO_EL0 now restored late
> > in the return-to-user path, we can otherwise use it to hold 'current'
> > and update the various accessors accordingly.
> >
> > Move 'current' from SP_EL0 to TPIDRRO_EL0.
>
> Is it worth having a #define for the name of the register that stores 'current'?
> (And probably the other similar registers.)
> That would avoid the bisection problems with the following two patches
> and might make other code a bit more readable.
We don't tend to reallocate 'current' all that often, so I don't think it's
worth the indirection tbh. The following patches are to a GDB script and
a bpf selftest, so I'm not going to lose sleep about bisection.
Will
next prev parent reply other threads:[~2026-09-11 12:57 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-07 16:42 [PATCH 00/21] arm64: Move overflow sp into SP_EL1 and kernel sp into SP_EL0 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 [this message]
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 ` [PATCH 00/21] arm64: Move overflow sp into SP_EL1 and kernel sp into SP_EL0 Vladimir Murzin
2026-09-09 11:29 ` Will Deacon
2026-09-10 13:49 ` Vladimir Murzin
2026-09-11 12:57 ` Will Deacon
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