From: Ard Biesheuvel <ardb@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: maz@kernel.org, rmk+kernel@armlinux.org.uk,
linus.walleij@linaro.org,
Ard Biesheuvel <ard.biesheuvel@linaro.org>
Subject: [PATCH v2 0/2] ARM/decompressor: deal with disabled CP15 barrier instructions
Date: Mon, 18 Nov 2019 19:15:41 +0100 [thread overview]
Message-ID: <20191118181543.122968-1-ardb@kernel.org> (raw)
From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
While trying to test my v4.4 backport of the firmware/hypervisor based spectre
v1/v2 mitigations for 32-bit ARM, I noticed that KVM/qemu failed to boot my
kernel while it booted fine under TCG emulation.
As it turns out, KVM/qemu may instantiate the VCPU with support for CP15
barrier instructions disabled, causing them to UNDEF and crash the
decompressor.
I already fixed the same issue for UEFI boot, but since v4.4 does not support
that, I only noticed now that this is an issue for bare metal as well.
Changes since v1:
- instead of using v7 barriers in the v7 code, enable the CP15 barriers - this
way, we can keep using the v7 routines for some v6 CPUs that implement CPUID
instructions (causing them to take the v7 path) but not for the v7 barriers.
- applied Marc's and Linus's acks to #2 only
I have tested this via kernelci [0], which includes the v6 pogoplug that got
broken by the v1 version of this series.
[0] https://kernelci.org/build/ardb/branch/for-kernelci/kernel/v5.4-rc8-2-gcaea8d2861c8/
Cc: Russell King <rmk+kernel@armlinux.org.uk>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Marc Zyngier <maz@kernel.org>
Ard Biesheuvel (2):
ARM/decompressor: enable CP15 barrier instructions in v7 cache setup
code
Revert "ARM: 8857/1: efi: enable CP15 DMB instructions before cleaning
the cache"
arch/arm/boot/compressed/head.S | 29 ++++++++++----------
1 file changed, 14 insertions(+), 15 deletions(-)
--
2.20.1
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next reply other threads:[~2019-11-18 18:16 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-18 18:15 Ard Biesheuvel [this message]
2019-11-18 18:15 ` [PATCH v2 1/2] ARM/decompressor: enable CP15 barrier instructions in v7 cache setup code Ard Biesheuvel
2019-11-18 18:15 ` [PATCH v2 2/2] Revert "ARM: 8857/1: efi: enable CP15 DMB instructions before cleaning the cache" Ard Biesheuvel
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