linux-kernel - Re: [patch 02/11] x86/time: Implement clocksource_arch

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Date:   Fri, 14 Sep 2018 17:45:06 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Matt Rickard <matt@...trans.com.au>,
        Stephen Boyd <sboyd@...nel.org>,
        John Stultz <john.stultz@...aro.org>,
        Florian Weimer <fweimer@...hat.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        devel@...uxdriverproject.org,
        virtualization@...ts.linux-foundation.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Arnd Bergmann <arnd@...db.de>, Juergen Gross <jgross@...e.com>
Subject: Re: [patch 02/11] x86/time: Implement clocksource_arch_init()

Thomas Gleixner <tglx@...utronix.de> writes:

> Runtime validate the VCLOCK_MODE in clocksource::archdata and disable
> VCLOCK if invalid, which disables the VDSO but keeps the system running.
>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  arch/x86/Kconfig       |    1 +
>  arch/x86/kernel/time.c |   16 ++++++++++++++++
>  2 files changed, 17 insertions(+)
>
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -48,6 +48,7 @@ config X86
>  	select ACPI_SYSTEM_POWER_STATES_SUPPORT	if ACPI
>  	select ANON_INODES
>  	select ARCH_CLOCKSOURCE_DATA
> +	select ARCH_CLOCKSOURCE_INIT
>  	select ARCH_DISCARD_MEMBLOCK
>  	select ARCH_HAS_ACPI_TABLE_UPGRADE	if ACPI
>  	select ARCH_HAS_DEBUG_VIRTUAL
> --- a/arch/x86/kernel/time.c
> +++ b/arch/x86/kernel/time.c
> @@ -10,6 +10,7 @@
>   *
>   */
>
> +#include <linux/clocksource.h>
>  #include <linux/clockchips.h>
>  #include <linux/interrupt.h>
>  #include <linux/irq.h>
> @@ -105,3 +106,18 @@ void __init time_init(void)
>  {
>  	late_time_init = x86_late_time_init;
>  }
> +
> +/*
> + * Sanity check the vdso related archdata content.
> + */
> +void clocksource_arch_init(struct clocksource *cs)
> +{
> +	if (cs->archdata.vclock_mode == VCLOCK_NONE)
> +		return;
> +
> +	if (cs->archdata.vclock_mode >= VCLOCK_MAX) {

It should be '>' as VCLOCK_MAX == VCLOCK_HVCLOCK == 3

> +		pr_warn("clocksource %s registered with invalid vclock_mode %d. Disabling vclock.\n",
> +			cs->name, cs->archdata.vclock_mode);
> +		cs->archdata.vclock_mode = VCLOCK_NONE;
> +	}
> +}

-- 
  Vitaly