From: Marc Zyngier <maz@kernel.org>
To: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu
Cc: Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
kernel-team@android.com, Ard Biesheuvel <ardb@kernel.org>
Subject: Re: [PATCH 00/17] arm64: Early CPU feature override, and an application to VHE
Date: Tue, 29 Dec 2020 19:27:14 +0000 [thread overview]
Message-ID: <20205dd2e203de92c680082eb3bf399e@kernel.org> (raw)
In-Reply-To: <20201228104958.1848833-1-maz@kernel.org>
On 2020-12-28 10:49, Marc Zyngier wrote:
> It recently came to light that there is a need to be able to override
> some CPU features very early on, before the kernel is fully up and
> running. The reasons for this range from specific feature support
> (such as using Protected KVM on VHE HW, which is the main motivation
> for this work) to errata workaround (a feature is broken on a CPU and
> needs to be turned off, or rather not enabled).
>
> This series tries to offer a limited framework for this kind of
> problems, by allowing a set of options to be passed on the
> command-line and altering the feature set that the cpufeature
> subsystem exposes to the rest of the kernel. Note that this doesn't
> change anything for code that directly uses the CPU ID registers.
>
> The series completely changes the way a VHE-capable arm64 boots, by
> *always* booting non-VHE first, and then upgrading to VHE when deemed
> capable. Although this sounds scary, this is actually simple to
> implement (and I wish I had though of it five years ago). The "upgrade
> to VHE" path is then conditioned on the VHE feature not being disabled
> from the command-line.
>
> Said command-line parsing borrows a lot from the kaslr code, and
> subsequently allows the "nokaslr" option to be moved to the new
> infrastructure (though it all looks a bit... odd).
>
> This has been tested on multiple VHE and non-VHE systems.
FWIW, I've just fixed a number of issues with this series, ranging
from compilation issues when CONFIG_RANDOMIZE_BASE is not set,
SPE setup bugs, and boot hangs when kaslr kicks in.
It all should be fixed now, and I have pushed an updated series
at [1], for those of you who really can't wait to try new stuff
while you could just ignore it all.
Thanks,
M.
[1]
https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=hack/arm64-early-cpufeature
--
Jazz is not dead. It just smells funny...
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WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <maz@kernel.org>
To: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu
Cc: Mark Rutland <mark.rutland@arm.com>,
Will Deacon <will@kernel.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
James Morse <james.morse@arm.com>,
David Brazdil <dbrazdil@google.com>,
kernel-team@android.com, Ard Biesheuvel <ardb@kernel.org>,
Julien Thierry <julien.thierry.kdev@gmail.com>
Subject: Re: [PATCH 00/17] arm64: Early CPU feature override, and an application to VHE
Date: Tue, 29 Dec 2020 19:27:14 +0000 [thread overview]
Message-ID: <20205dd2e203de92c680082eb3bf399e@kernel.org> (raw)
In-Reply-To: <20201228104958.1848833-1-maz@kernel.org>
On 2020-12-28 10:49, Marc Zyngier wrote:
> It recently came to light that there is a need to be able to override
> some CPU features very early on, before the kernel is fully up and
> running. The reasons for this range from specific feature support
> (such as using Protected KVM on VHE HW, which is the main motivation
> for this work) to errata workaround (a feature is broken on a CPU and
> needs to be turned off, or rather not enabled).
>
> This series tries to offer a limited framework for this kind of
> problems, by allowing a set of options to be passed on the
> command-line and altering the feature set that the cpufeature
> subsystem exposes to the rest of the kernel. Note that this doesn't
> change anything for code that directly uses the CPU ID registers.
>
> The series completely changes the way a VHE-capable arm64 boots, by
> *always* booting non-VHE first, and then upgrading to VHE when deemed
> capable. Although this sounds scary, this is actually simple to
> implement (and I wish I had though of it five years ago). The "upgrade
> to VHE" path is then conditioned on the VHE feature not being disabled
> from the command-line.
>
> Said command-line parsing borrows a lot from the kaslr code, and
> subsequently allows the "nokaslr" option to be moved to the new
> infrastructure (though it all looks a bit... odd).
>
> This has been tested on multiple VHE and non-VHE systems.
FWIW, I've just fixed a number of issues with this series, ranging
from compilation issues when CONFIG_RANDOMIZE_BASE is not set,
SPE setup bugs, and boot hangs when kaslr kicks in.
It all should be fixed now, and I have pushed an updated series
at [1], for those of you who really can't wait to try new stuff
while you could just ignore it all.
Thanks,
M.
[1]
https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=hack/arm64-early-cpufeature
--
Jazz is not dead. It just smells funny...
_______________________________________________
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next prev parent reply other threads:[~2020-12-29 19:27 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-28 10:49 [PATCH 00/17] arm64: Early CPU feature override, and an application to VHE Marc Zyngier
2020-12-28 10:49 ` Marc Zyngier
2020-12-28 10:49 ` [PATCH 01/17] arm64: Fix labels in el2_setup macros Marc Zyngier
2020-12-28 10:49 ` Marc Zyngier
2020-12-28 10:49 ` [PATCH 02/17] arm64: Fix outdated TCR setup comment Marc Zyngier
2020-12-28 10:49 ` Marc Zyngier
2020-12-28 10:49 ` [PATCH 03/17] arm64: Turn the MMU-on sequence into a macro Marc Zyngier
2020-12-28 10:49 ` Marc Zyngier
2020-12-28 10:49 ` [PATCH 04/17] arm64: Provide an 'upgrade to VHE' stub hypercall Marc Zyngier
2020-12-28 10:49 ` Marc Zyngier
2021-01-04 23:39 ` Jing Zhang
2021-01-04 23:39 ` Jing Zhang
2021-01-05 8:24 ` Marc Zyngier
2021-01-05 8:24 ` Marc Zyngier
2020-12-28 10:49 ` [PATCH 05/17] arm64: Initialise as nVHE before switching to VHE Marc Zyngier
2020-12-28 10:49 ` Marc Zyngier
2020-12-28 10:49 ` [PATCH 06/17] arm64: Move VHE-specific SPE setup to mutate_to_vhe() Marc Zyngier
2020-12-28 10:49 ` Marc Zyngier
2020-12-28 10:49 ` [PATCH 07/17] arm64: Simplify init_el2_state to be non-VHE only Marc Zyngier
2020-12-28 10:49 ` Marc Zyngier
2020-12-28 10:49 ` [PATCH 08/17] arm64: Move SCTLR_EL1 initialisation to EL-agnostic code Marc Zyngier
2020-12-28 10:49 ` Marc Zyngier
2020-12-28 10:49 ` [PATCH 09/17] arm64: cpufeature: Add global feature override facility Marc Zyngier
2020-12-28 10:49 ` Marc Zyngier
2020-12-28 10:49 ` [PATCH 10/17] arm64: Extract early FDT mapping from kaslr_early_init() Marc Zyngier
2020-12-28 10:49 ` Marc Zyngier
2020-12-28 10:49 ` [PATCH 11/17] arm64: cpufeature: Add an early command-line cpufeature override facility Marc Zyngier
2020-12-28 10:49 ` Marc Zyngier
2020-12-28 10:49 ` [PATCH 12/17] arm64: Allow ID_AA64MMFR1_EL1.VH to be overridden from the command line Marc Zyngier
2020-12-28 10:49 ` Marc Zyngier
2020-12-28 10:49 ` [PATCH 13/17] arm64: Honor VHE being disabled from the command-line Marc Zyngier
2020-12-28 10:49 ` Marc Zyngier
2020-12-28 10:49 ` [PATCH 14/17] arm64: Add an aliasing facility for the idreg override Marc Zyngier
2020-12-28 10:49 ` Marc Zyngier
2020-12-28 10:49 ` [PATCH 15/17] arm64: Make kvm-arm.mode={nvhe, protected} an alias of id_aa64mmfr1.vh=0 Marc Zyngier
2020-12-28 10:49 ` Marc Zyngier
2020-12-28 10:49 ` [PATCH 16/17] KVM: arm64: Document HVC_VHE_RESTART stub hypercall Marc Zyngier
2020-12-28 10:49 ` Marc Zyngier
2020-12-28 10:49 ` [PATCH 17/17] arm64: Move "nokaslr" over to the early cpufeature infrastructure Marc Zyngier
2020-12-28 10:49 ` Marc Zyngier
2020-12-29 19:27 ` Marc Zyngier [this message]
2020-12-29 19:27 ` [PATCH 00/17] arm64: Early CPU feature override, and an application to VHE Marc Zyngier
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