[MODERATED] Re: [PATCH v5 5/8] L1TFv4 0

[Borislav Petkov <bp@suse.de>]

On Wed, May 23, 2018 at 02:51:22PM -0700, speck for Andi Kleen wrote:
> From: Andi Kleen <ak@linux.intel.com>
> Subject:  x86, l1tf: Add sysfs reporting for l1tf
> 
> L1TF core kernel workarounds are cheap and normally always enabled,
> However we still want to report in sysfs if the system is vulnerable
> or mitigated. Add the necessary checks.
> 
> - We use the same checks as Meltdown to determine if the system is
> vulnerable. This excludes some Atom CPUs which don't have this
> problem.
> - We check for the (very unlikely) memory > MAX_PA/2 case
> - We check for 32bit non PAE and warn
> 
> Note this patch will likely conflict with some other workaround patches
> floating around, but should be straight forward to fix.

...

> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
> index 7416fc206b4a..6b557f069a6f 100644
> --- a/arch/x86/kernel/cpu/bugs.c
> +++ b/arch/x86/kernel/cpu/bugs.c
> @@ -707,4 +707,15 @@ ssize_t cpu_show_spec_store_bypass(struct device *dev, struct device_attribute *
>  {
>  	return cpu_show_common(dev, attr, buf, X86_BUG_SPEC_STORE_BYPASS);
>  }
> +
> +ssize_t cpu_show_l1tf(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	if (!boot_cpu_has_bug(X86_BUG_L1TF))
> +		return sprintf(buf, "Not affected\n");

In your other patches you should test the bug flag X86_BUG_L1TF like
here, not with boot_cpu_has().

It works now but we might enforce it someday.

> +
> +	if (boot_cpu_has(X86_FEATURE_L1TF_WA))
> +		return sprintf(buf, "Mitigated\n");
> +
> +	return sprintf(buf, "Vulnerable\n");
> +}

Make that cpu_show_l1tf() call cpu_show_common() like the others do.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
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