linux-kernel - Re: [PATCH v6 00/10] arm64: add system vulnerability sysfs entries

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Message-ID: <20190325103344.704cbb74@donnerap.cambridge.arm.com>
Date:   Mon, 25 Mar 2019 10:33:44 +0000
From:   Andre Przywara <andre.przywara@....com>
To:     Jeremy Linton <jeremy.linton@....com>
Cc:     <linux-arm-kernel@...ts.infradead.org>, <catalin.marinas@....com>,
        <will.deacon@....com>, <marc.zyngier@....com>,
        <suzuki.poulose@....com>, <Dave.Martin@....com>,
        <shankerd@...eaurora.org>, <julien.thierry@....com>,
        <mlangsdo@...hat.com>, <stefan.wahren@....com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 00/10] arm64: add system vulnerability sysfs entries

On Thu, 21 Mar 2019 18:05:47 -0500
Jeremy Linton <jeremy.linton@....com> wrote:

Hi,

> Arm64 machines should be displaying a human readable
> vulnerability status to speculative execution attacks in
> /sys/devices/system/cpu/vulnerabilities 
> 
> This series enables that behavior by providing the expected
> functions. Those functions expose the cpu errata and feature
> states, as well as whether firmware is responding appropriately
> to display the overall machine status. This means that in a
> heterogeneous machine we will only claim the machine is mitigated
> or safe if we are confident all booted cores are safe or
> mitigated.
> 
> v5->v6:
> 	Invert meltdown logic to display that a core is safe rather
> 	       than mitigated if the mitigation has been enabled on
> 	       machines that are safe. This can happen when the
> 	       mitigation was forced on via command line or KASLR.
> 	       This means that in order to detect if kpti is enabled
> 	       other methods must be used (look at dmesg) when the
> 	       machine isn't itself susceptible to meltdown.
> 	Trivial whitespace tweaks.

Thanks for those changes, I am happy with them. The whole series looks
ready to me now.

Cheers,
Andre.

> v4->v5:
> 	Revert the changes to remove the CONFIG_EXPERT hidden
> 	       options, but leave the detection paths building
> 	       without #ifdef wrappers. Also remove the
> 	       CONFIG_GENERIC_CPU_VULNERABILITIES #ifdefs
> 	       as we are 'select'ing the option in the Kconfig.
> 	       This allows us to keep all three variations of
> 	       the CONFIG/enable/disable paths without a lot of
> 	       (CONFIG_X || CONFIG_Y) checks.
> 	Various bits/pieces moved between the patches in an attempt
> 		to keep similar features/changes together.
> 
> v3->v4:
>         Drop the patch which selectivly exports sysfs entries
>         Remove the CONFIG_EXPERT hidden options which allowed
>                the kernel to be built without the vulnerability
>                detection code.
>         Pick Marc Z's patches which invert the white/black
>                lists for spectrev2 and clean up the firmware
>                detection logic.
>         Document the existing kpti controls
>         Add a nospectre_v2 option to boot time disable the
>              mitigation
> 
> v2->v3:
>         Remove "Unknown" states, replace with further blacklists
>                and default vulnerable/not affected states.
>         Add the ability for an arch port to selectively export
>                sysfs vulnerabilities.
> 
> v1->v2:
>         Add "Unknown" state to ABI/testing docs.
>         Minor tweaks.
> 
> Jeremy Linton (6):
>   arm64: Provide a command line to disable spectre_v2 mitigation
>   arm64: add sysfs vulnerability show for meltdown
>   arm64: Always enable spectrev2 vulnerability detection
>   arm64: add sysfs vulnerability show for spectre v2
>   arm64: Always enable ssb vulnerability detection
>   arm64: add sysfs vulnerability show for speculative store bypass
> 
> Marc Zyngier (2):
>   arm64: Advertise mitigation of Spectre-v2, or lack thereof
>   arm64: Use firmware to detect CPUs that are not affected by Spectre-v2
> 
> Mian Yousaf Kaukab (2):
>   arm64: add sysfs vulnerability show for spectre v1
>   arm64: enable generic CPU vulnerabilites support
> 
>  .../admin-guide/kernel-parameters.txt         |   8 +-
>  arch/arm64/Kconfig                            |   1 +
>  arch/arm64/include/asm/cpufeature.h           |   4 -
>  arch/arm64/kernel/cpu_errata.c                | 239 +++++++++++++-----
>  arch/arm64/kernel/cpufeature.c                |  58 ++++-
>  5 files changed, 223 insertions(+), 87 deletions(-)
>