Re: [PATCH] L1TF support in PowerPC SYSFS.

[Michael Ellerman <mpe@ellerman.id.au>]

Hi Anthony,

Thanks for the patch.

asteinhauser@google.com writes:
> From: Anthony Steinhauser <asteinhauser@google.com>
>
> PowerPC CPUs are vulnerable to L1TF to the same extent as to Meltdown.
> It is also mitigated by flushing the L1D on privilege transition.
> Currently the SYSFS gives a false negative on L1TF on CPUs that I verified
> to be vulnerable.

Can you include the details of which CPUs you tested?

> https://www.ibm.com/blogs/psirt/potential-impact-processors-power-family/
> https://github.com/google/safeside/pull/52
> Signed-off-by: Anthony Steinhauser <asteinhauser@google.com>
> ---

I don't usually retain links in the change log, because they bit rot, so
I'll drop those, but they will remain in the email archive.

> diff --git a/arch/powerpc/kernel/security.c b/arch/powerpc/kernel/security.c
> index 7cfcb294b11c..a1a5017c5170 100644
> --- a/arch/powerpc/kernel/security.c
> +++ b/arch/powerpc/kernel/security.c
> @@ -135,7 +135,8 @@ void setup_spectre_v2(void)
>  #endif /* CONFIG_PPC_FSL_BOOK3E */
>  
>  #ifdef CONFIG_PPC_BOOK3S_64
> -ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
> +static ssize_t cpu_show_delayed_fault_common(

I guess that's an accurate name.

I probably would have just had cpu_show_l1tf() call cpu_show_meltdown(),
but I guess either approach is fine.

cheers


> @@ -167,6 +168,16 @@ ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, cha
>  
>  	return sprintf(buf, "Vulnerable\n");
>  }
> +
> +ssize_t cpu_show_l1tf(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	return cpu_show_delayed_fault_common(dev, attr, buf);
> +}
> +
> +ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	return cpu_show_delayed_fault_common(dev, attr, buf);
> +}
>  #endif
>  
>  ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, char *buf)
> -- 
> 2.24.0.rc0.303.g954a862665-goog