linux-kernel - Re: [PATCH v3 1/7] sysfs/cpu: Allow individual architectures to select vulnerabilities

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Date:   Fri, 18 Jan 2019 16:46:37 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     jeremy.linton@....com, linux-arm-kernel@...ts.infradead.org,
        catalin.marinas@....com, will.deacon@....com, marc.zyngier@....com,
        dave.martin@....com, shankerd@...eaurora.org,
        linux-kernel@...r.kernel.org, ykaukab@...e.de,
        julien.thierry@....com, mlangsdo@...hat.com, Steven.Price@....com,
        stefan.wahren@...e.com, rafael@...nel.org, tglx@...utronix.de,
        jpoimboe@...hat.com, konrad.wilk@...cle.com, mingo@...nel.org,
        longman@...hat.com, ak@...ux.intel.com, jkosina@...e.cz
Subject: Re: [PATCH v3 1/7] sysfs/cpu: Allow individual architectures to
 select vulnerabilities

On Mon, Jan 14, 2019 at 10:02:21AM +0000, Suzuki K Poulose wrote:
> 
> 
> On 09/01/2019 23:55, Jeremy Linton wrote:
> > As suggested on the list, https://lkml.org/lkml/2019/1/4/282, there are
> > a number of cases where its useful for a system to avoid exporting a
> > sysfs entry for a given vulnerability. This set adds an architecture
> > specific callback which returns the bitmap of vulnerabilities the
> > architecture would like to advertise.
> > 
> > Signed-off-by: Jeremy Linton <jeremy.linton@....com>
> > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > Cc: Rafael J. Wysocki <rafael@...nel.org>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: Josh Poimboeuf <jpoimboe@...hat.com>
> > Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> > Cc: Ingo Molnar <mingo@...nel.org>
> > Cc: Waiman Long <longman@...hat.com>
> > Cc: Andi Kleen <ak@...ux.intel.com>
> > Cc: Jiri Kosina <jkosina@...e.cz>
> > ---
> >   drivers/base/cpu.c  | 19 +++++++++++++++++++
> >   include/linux/cpu.h |  7 +++++++
> >   2 files changed, 26 insertions(+)
> > 
> > diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
> > index eb9443d5bae1..35f6dfb24cd6 100644
> > --- a/drivers/base/cpu.c
> > +++ b/drivers/base/cpu.c
> > @@ -561,6 +561,11 @@ static struct attribute *cpu_root_vulnerabilities_attrs[] = {
> >   	NULL
> >   };
> > +uint __weak arch_supported_vuln_attr_fields(void)
> > +{
> > +	return VULN_MELTDOWN|VULN_SPECTREV1|VULN_SPECTREV2|VULN_SSB|VULN_L1TF;
> > +}
> > +
> >   static const struct attribute_group cpu_root_vulnerabilities_group = {
> >   	.name  = "vulnerabilities",
> >   	.attrs = cpu_root_vulnerabilities_attrs,
> > @@ -568,6 +573,20 @@ static const struct attribute_group cpu_root_vulnerabilities_group = {
> >   static void __init cpu_register_vulnerabilities(void)
> >   {
> > +	int fld;
> > +	int max_fields = ARRAY_SIZE(cpu_root_vulnerabilities_attrs) - 1;
> > +	struct attribute **hd = cpu_root_vulnerabilities_attrs;
> > +	uint enabled_fields = arch_supported_vuln_attr_fields();
> > +
> > +	/* only enable entries requested by the arch code */
> > +	for (fld = 0; fld < max_fields; fld++) {
> > +		if (enabled_fields & 1 << fld) {
> > +			*hd = cpu_root_vulnerabilities_attrs[fld];
> > +			hd++;
> > +		}
> > +	}
> > +	*hd = NULL;
> > +
> 
> nit: Could we use "is_visible" callback in the attribute group to check this
> dynamically ?

You should, that is what it is there for.

thanks,

greg k-h