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From: Marc Zyngier <maz@kernel.org>
To: David Brazdil <dbrazdil@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Jing Zhang <jingzhangos@google.com>,
	kernel-team@android.com, Srinivas Ramana <sramana@codeaurora.org>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	linux-kernel@vger.kernel.org, Ard Biesheuvel <ardb@kernel.org>,
	James Morse <james.morse@arm.com>,
	Julien Thierry <julien.thierry.kdev@gmail.com>,
	Ajay Patil <pajay@qti.qualcomm.com>,
	Prasad Sodagudi <psodagud@codeaurora.org>,
	Will Deacon <will@kernel.org>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v4 18/21] arm64: Move "nokaslr" over to the early cpufeature infrastructure
Date: Sun, 24 Jan 2021 18:41:19 +0000	[thread overview]
Message-ID: <87tur6jhyo.wl-maz@kernel.org> (raw)
In-Reply-To: <20210118144636.kysdvnmcdm7it5zp@google.com>

On Mon, 18 Jan 2021 14:46:36 +0000,
David Brazdil <dbrazdil@google.com> wrote:
> 
> On Mon, Jan 18, 2021 at 09:45:30AM +0000, Marc Zyngier wrote:
> > Given that the early cpufeature infrastructure has borrowed quite
> > a lot of code from the kaslr implementation, let's reimplement
> > the matching of the "nokaslr" option with it.
> > 
> > Signed-off-by: Marc Zyngier <maz@kernel.org>
> Acked-by: David Brazdil <dbrazdil@google.com>

[...]

> > @@ -126,7 +95,7 @@ u64 __init kaslr_early_init(void)
> >  	 * Check if 'nokaslr' appears on the command line, and
> >  	 * return 0 if that is the case.
> >  	 */
> > -	if (is_kaslr_disabled_cmdline(fdt)) {
> > +	if (kaslr_feature_val & kaslr_feature_mask & 0xf) {
> 
> nit: Isn't the 0xf redundant here? You don't re-mask for VH either.

Actually, I do. See the two back to back ubfx that extract both the
mask and the feature. The "& 0xf" here serves the same purpose.

Is it redundant? At the moment, quite possibly. But since we have
space for 16 "features", this is an indication that we are only using
the first one. I expect that eventually, we'll use it for other
things.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

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  reply	other threads:[~2021-01-24 18:42 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-18  9:45 [PATCH v4 00/21] arm64: Early CPU feature override, and applications to VHE, BTI and PAuth Marc Zyngier
2021-01-18  9:45 ` [PATCH v4 01/21] arm64: Fix labels in el2_setup macros Marc Zyngier
2021-01-18 11:13   ` David Brazdil
2021-01-18  9:45 ` [PATCH v4 02/21] arm64: Fix outdated TCR setup comment Marc Zyngier
2021-01-20 18:18   ` Catalin Marinas
2021-01-18  9:45 ` [PATCH v4 03/21] arm64: Turn the MMU-on sequence into a macro Marc Zyngier
2021-01-20 18:18   ` Catalin Marinas
2021-01-18  9:45 ` [PATCH v4 04/21] arm64: Provide an 'upgrade to VHE' stub hypercall Marc Zyngier
2021-01-18 11:25   ` David Brazdil
2021-01-24 18:44     ` Marc Zyngier
2021-01-18  9:45 ` [PATCH v4 05/21] arm64: Initialise as nVHE before switching to VHE Marc Zyngier
2021-01-18  9:45 ` [PATCH v4 06/21] arm64: Move VHE-specific SPE setup to mutate_to_vhe() Marc Zyngier
2021-01-18  9:45 ` [PATCH v4 07/21] arm64: Simplify init_el2_state to be non-VHE only Marc Zyngier
2021-01-18  9:45 ` [PATCH v4 08/21] arm64: Move SCTLR_EL1 initialisation to EL-agnostic code Marc Zyngier
2021-01-20 18:35   ` Catalin Marinas
2021-01-18  9:45 ` [PATCH v4 09/21] arm64: cpufeature: Add global feature override facility Marc Zyngier
2021-01-22 18:41   ` Catalin Marinas
2021-01-23 15:59   ` Suzuki K Poulose
2021-01-18  9:45 ` [PATCH v4 10/21] arm64: cpufeature: Use IDreg override in __read_sysreg_by_encoding() Marc Zyngier
2021-01-22 18:53   ` Catalin Marinas
2021-01-23 16:04     ` Suzuki K Poulose
2021-01-18  9:45 ` [PATCH v4 11/21] arm64: Extract early FDT mapping from kaslr_early_init() Marc Zyngier
2021-01-22 18:55   ` Catalin Marinas
2021-01-23 13:25   ` Catalin Marinas
2021-01-18  9:45 ` [PATCH v4 12/21] arm64: cpufeature: Add an early command-line cpufeature override facility Marc Zyngier
2021-01-18 13:07   ` David Brazdil
2021-01-23 13:23   ` Catalin Marinas
2021-01-23 13:43   ` Catalin Marinas
2021-01-24 16:21     ` Marc Zyngier
2021-01-18  9:45 ` [PATCH v4 13/21] arm64: Allow ID_AA64MMFR1_EL1.VH to be overridden from the command line Marc Zyngier
2021-01-23 14:04   ` Catalin Marinas
2021-01-18  9:45 ` [PATCH v4 14/21] arm64: Honor VHE being disabled from the command-line Marc Zyngier
2021-01-18 13:14   ` David Brazdil
2021-01-23 14:07   ` Catalin Marinas
2021-01-24 15:59     ` Marc Zyngier
2021-01-18  9:45 ` [PATCH v4 15/21] arm64: Add an aliasing facility for the idreg override Marc Zyngier
2021-01-18 13:18   ` David Brazdil
2021-01-24 19:01     ` Marc Zyngier
2021-01-23 14:12   ` Catalin Marinas
2021-01-18  9:45 ` [PATCH v4 16/21] arm64: Make kvm-arm.mode={nvhe, protected} an alias of id_aa64mmfr1.vh=0 Marc Zyngier
2021-01-23 14:15   ` [PATCH v4 16/21] arm64: Make kvm-arm.mode={nvhe,protected} " Catalin Marinas
2021-01-18  9:45 ` [PATCH v4 17/21] KVM: arm64: Document HVC_VHE_RESTART stub hypercall Marc Zyngier
2021-01-18 13:29   ` David Brazdil
2021-01-18  9:45 ` [PATCH v4 18/21] arm64: Move "nokaslr" over to the early cpufeature infrastructure Marc Zyngier
2021-01-18 14:46   ` David Brazdil
2021-01-24 18:41     ` Marc Zyngier [this message]
2021-01-23 14:19   ` Catalin Marinas
2021-01-18  9:45 ` [PATCH v4 19/21] arm64: cpufeatures: Allow disabling of BTI from the command-line Marc Zyngier
2021-01-23 14:24   ` Catalin Marinas
2021-01-18  9:45 ` [PATCH v4 20/21] arm64: Defer enabling pointer authentication on boot core Marc Zyngier
2021-01-23 14:26   ` Catalin Marinas
2021-01-18  9:45 ` [PATCH v4 21/21] arm64: cpufeatures: Allow disabling of Pointer Auth from the command-line Marc Zyngier
2021-01-23 14:28   ` Catalin Marinas
2021-01-18 14:54 ` [PATCH v4 00/21] arm64: Early CPU feature override, and applications to VHE, BTI and PAuth David Brazdil

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