From: Srinivas Ramana <sramana@codeaurora.org>
To: Catalin Marinas <catalin.marinas@arm.com>, Marc Zyngier <maz@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org,
Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
David Brazdil <dbrazdil@google.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
Ard Biesheuvel <ardb@kernel.org>,
Jing Zhang <jingzhangos@google.com>,
Ajay Patil <pajay@qti.qualcomm.com>,
Prasad Sodagudi <psodagud@codeaurora.org>,
James Morse <james.morse@arm.com>,
Julien Thierry <julien.thierry.kdev@gmail.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
kernel-team@android.com
Subject: Re: [PATCH v3 09/21] arm64: cpufeature: Add global feature override facility
Date: Mon, 11 Jan 2021 12:38:43 -0800 [thread overview]
Message-ID: <de9d8631-4ff9-9d0c-e4eb-5ce0eeb0ecea@codeaurora.org> (raw)
In-Reply-To: <20210111184154.GC17941@gaia>
Hi Catalin,
On 1/11/2021 10:41 AM, Catalin Marinas wrote:
> Hi Marc,
>
> On Mon, Jan 11, 2021 at 01:27:59PM +0000, Marc Zyngier wrote:
>> Add a facility to globally override a feature, no matter what
>> the HW says. Yes, this is dangerous.
> Yeah, it's dangerous. We can make it less so if we only allow safe
> values (e.g. lower if FTR_UNSIGNED).
>
>> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
>> index 9a555809b89c..465d2cb63bfc 100644
>> --- a/arch/arm64/include/asm/cpufeature.h
>> +++ b/arch/arm64/include/asm/cpufeature.h
>> @@ -75,6 +75,8 @@ struct arm64_ftr_reg {
>> u64 sys_val;
>> u64 user_val;
>> const struct arm64_ftr_bits *ftr_bits;
>> + u64 *override_val;
>> + u64 *override_mask;
>> };
> At the arm64_ftr_reg level, we don't have any information about the safe
> values for a feature. Could we instead move this to arm64_ftr_bits? We
> probably only need a single field. When populating the feature values,
> we can make sure it doesn't go above the hardware one.
>
> I attempted a feature modification for MTE here, though I dropped the
> entire series in the meantime as we clarified the ARM ARM:
>
> https://lore.kernel.org/linux-arm-kernel/20200515171612.1020-24-catalin.marinas@arm.com/
>
> Srinivas copied it in his patch (but forgot to give credit ;)):
Sorry about that. I did mention that its taken from your patch-set in my
cover letter. But missed your signed-off-by in the patch.
https://lore.kernel.org/linux-arm-msm/6dfdf691b5ed57df81c4c61422949af5@misterjones.org/T/#m1ae76e6096c07ab5f1636a4e383a3fd6cfb4665f
Since we can ignore my patch with the mechanism added by Marc, I am not
re-sending this. Thanks.
>
> https://lore.kernel.org/linux-arm-msm/1610152163-16554-3-git-send-email-sramana@codeaurora.org/
>
> The above adds a filter function but, instead, just use your mechanism in
> this series for idreg.feature setting via cmdline. The arm64_ftr_value()
> function extracts the hardware value and lowers it if a cmdline argument
> was passed.
>
next prev parent reply other threads:[~2021-01-11 20:40 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-11 13:27 [PATCH v3 00/21] arm64: Early CPU feature override, and applications to VHE, BTI and PAuth Marc Zyngier
2021-01-11 13:27 ` [PATCH v3 01/21] arm64: Fix labels in el2_setup macros Marc Zyngier
2021-01-11 13:27 ` [PATCH v3 02/21] arm64: Fix outdated TCR setup comment Marc Zyngier
2021-01-11 13:27 ` [PATCH v3 03/21] arm64: Turn the MMU-on sequence into a macro Marc Zyngier
2021-01-11 13:27 ` [PATCH v3 04/21] arm64: Provide an 'upgrade to VHE' stub hypercall Marc Zyngier
2021-01-11 13:53 ` Marc Zyngier
2021-01-11 13:27 ` [PATCH v3 05/21] arm64: Initialise as nVHE before switching to VHE Marc Zyngier
2021-01-11 13:27 ` [PATCH v3 06/21] arm64: Move VHE-specific SPE setup to mutate_to_vhe() Marc Zyngier
2021-01-11 13:27 ` [PATCH v3 07/21] arm64: Simplify init_el2_state to be non-VHE only Marc Zyngier
2021-01-11 13:27 ` [PATCH v3 08/21] arm64: Move SCTLR_EL1 initialisation to EL-agnostic code Marc Zyngier
2021-01-11 13:27 ` [PATCH v3 09/21] arm64: cpufeature: Add global feature override facility Marc Zyngier
2021-01-11 18:41 ` Catalin Marinas
2021-01-11 19:48 ` Marc Zyngier
2021-01-12 9:17 ` Suzuki K Poulose
2021-01-12 11:50 ` Marc Zyngier
2021-01-12 11:51 ` Marc Zyngier
2021-01-12 12:20 ` Suzuki K Poulose
2021-01-12 11:59 ` Suzuki K Poulose
2021-01-12 14:54 ` Marc Zyngier
2021-01-11 20:38 ` Srinivas Ramana [this message]
2021-01-11 13:28 ` [PATCH v3 10/21] arm64: cpufeature: Use IDreg override in __read_sysreg_by_encoding() Marc Zyngier
2021-01-11 13:28 ` [PATCH v3 11/21] arm64: Extract early FDT mapping from kaslr_early_init() Marc Zyngier
2021-01-11 13:28 ` [PATCH v3 12/21] arm64: cpufeature: Add an early command-line cpufeature override facility Marc Zyngier
2021-01-11 13:28 ` [PATCH v3 13/21] arm64: Allow ID_AA64MMFR1_EL1.VH to be overridden from the command line Marc Zyngier
2021-01-11 13:28 ` [PATCH v3 14/21] arm64: Honor VHE being disabled from the command-line Marc Zyngier
2021-01-11 13:28 ` [PATCH v3 15/21] arm64: Add an aliasing facility for the idreg override Marc Zyngier
2021-01-11 13:28 ` [PATCH v3 16/21] arm64: Make kvm-arm.mode={nvhe,protected} an alias of id_aa64mmfr1.vh=0 Marc Zyngier
2021-01-11 13:28 ` [PATCH v3 17/21] KVM: arm64: Document HVC_VHE_RESTART stub hypercall Marc Zyngier
2021-01-11 13:28 ` [PATCH v3 18/21] arm64: Move "nokaslr" over to the early cpufeature infrastructure Marc Zyngier
2021-01-11 13:28 ` [PATCH v3 19/21] arm64: cpufeatures: Allow disabling of BTI from the command-line Marc Zyngier
2021-01-11 13:28 ` [PATCH v3 20/21] arm64: Defer enabling pointer authentication on boot core Marc Zyngier
2021-01-11 13:28 ` [PATCH v3 21/21] arm64: cpufeatures: Allow disabling of Pointer Auth from the command-line Marc Zyngier
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