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SubjectRe: [PATCH v3 1/7] sysfs/cpu: Allow individual architectures to select vulnerabilities
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On 01/18/2019 09:46 AM, Greg KH wrote:
> 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@arm.com>
>>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>> Cc: Rafael J. Wysocki <rafael@kernel.org>
>>> Cc: Thomas Gleixner <tglx@linutronix.de>
>>> Cc: Josh Poimboeuf <jpoimboe@redhat.com>
>>> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>>> Cc: Ingo Molnar <mingo@kernel.org>
>>> Cc: Waiman Long <longman@redhat.com>
>>> Cc: Andi Kleen <ak@linux.intel.com>
>>> Cc: Jiri Kosina <jkosina@suse.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.


Yes, its a good suggestion. OTOH, I think the plan is to drop this
functionality all together by removing the ability to build kernels
without the vulnerability checking/processor white lists. That will
simplify some of the #ifdef'ing going on as well.




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