Re: [PATCH 1/6] ARM: spectre-bhb: enable for Cortex-A15

[Jon Hunter <jonathanh@nvidia.com>]

Hi Ard,

On 28/03/2022 14:47, Ard Biesheuvel wrote:
> The Spectre-BHB mitigations were inadvertently left disabled for
> Cortex-A15, due to the fact that cpu_v7_bugs_init() is not called in
> that case. So fix that.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
>   arch/arm/mm/proc-v7-bugs.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm/mm/proc-v7-bugs.c b/arch/arm/mm/proc-v7-bugs.c
> index 06dbfb968182..fb9f3eb6bf48 100644
> --- a/arch/arm/mm/proc-v7-bugs.c
> +++ b/arch/arm/mm/proc-v7-bugs.c
> @@ -288,6 +288,7 @@ void cpu_v7_ca15_ibe(void)
>   {
>   	if (check_spectre_auxcr(this_cpu_ptr(&spectre_warned), BIT(0)))
>   		cpu_v7_spectre_v2_init();
> +	cpu_v7_spectre_bhb_init();
>   }
>   
>   void cpu_v7_bugs_init(void)


Since this patch has been merged, I am seeing a ton of messages when 
booting Linux on tegra124-jetson-tk1 ...

[ 1233.327547] CPU0: Spectre BHB: using loop workaround
[ 1233.327795] CPU1: Spectre BHB: using loop workaround
[ 1233.328270] CPU1: Spectre BHB: using loop workaround
[ 1233.328700] CPU1: Spectre BHB: using loop workaround
[ 1233.355477] CPU2: Spectre BHB: using loop workaround
** 7 printk messages dropped **
[ 1233.366271] CPU0: Spectre BHB: using loop workaround
[ 1233.366580] CPU0: Spectre BHB: using loop workaround
[ 1233.366815] CPU1: Spectre BHB: using loop workaround
[ 1233.405475] CPU1: Spectre BHB: using loop workaround
[ 1233.405874] CPU0: Spectre BHB: using loop workaround
[ 1233.406041] CPU1: Spectre BHB: using loop workaround
** 1 printk messages dropped **

This is significantly increasing the boot time and causing failures if 
the boot takes too long.

I see that Dmitry has posted a fix for one of these cases [0], but the 
above also needs to be fixed.

Thanks
Jon


[0] 
https://lore.kernel.org/linux-arm-kernel/20220519161310.1489625-1-dmitry.osipenko@collabora.com/T/
-- 
nvpublic