linux-kernel - [PATCH 0/2] Improve POE handling for uaccess

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Message-ID: <20250619160042.2499290-1-kevin.brodsky@arm.com>
Date: Thu, 19 Jun 2025 17:00:40 +0100
From: Kevin Brodsky <kevin.brodsky@....com>
To: linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org,
	Kevin Brodsky <kevin.brodsky@....com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Joey Gouly <joey.gouly@....com>,
	Will Deacon <will@...nel.org>
Subject: [PATCH 0/2] Improve POE handling for uaccess

This short series attempts to approach POE (Overlay) faults consistently
w.r.t. uaccess. We currently assume that spurious Overlay faults are
handled by retrying the access [1], but this isn't the case.

Patch 1 ensures that spurious Overlay faults are indeed ignored. This
being done, it typically isn't worth using an ISB when writing to
POR_EL0. Patch 2 removes the remaining ISB in the signal handling code.

Patch 1 changes the fault handling logic to rely solely on POR_EL0 and
VMA metadata to determine if a pkey fault occurred, instead of the
Overlay bit in ESR_EL1. The rationale is detailed in that patch; it
is worth noting that powerpc made a similar change but for a different
reason [2].

[1] https://lore.kernel.org/linux-arm-kernel/ZtYNGBrcE-j35fpw@arm.com/
[2] https://lore.kernel.org/all/20200505071729.54912-3-aneesh.kumar@linux.ibm.com/
---
Cc: "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Joey Gouly <joey.gouly@....com>
Cc: Will Deacon <will@...nel.org>
---

Kevin Brodsky (2):
  arm64: poe: Handle spurious Overlay faults
  arm64: signal: Remove ISB when resetting POR_EL0

 arch/arm64/kernel/process.c |  5 +++++
 arch/arm64/kernel/signal.c  |  7 +++++--
 arch/arm64/mm/fault.c       | 30 +++++++++++++++++++++---------
 3 files changed, 31 insertions(+), 11 deletions(-)

base-commit: e04c78d86a9699d136910cfc0bdcf01087e3267e
-- 
2.47.0