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SubjectRe: [PATCH v3 1/7] sysfs/cpu: Allow individual architectures to select vulnerabilities
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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 ?

> if (sysfs_create_group(&cpu_subsys.dev_root->kobj,
> &cpu_root_vulnerabilities_group))
> pr_err("Unable to register CPU vulnerabilities\n");
> diff --git a/include/linux/cpu.h b/include/linux/cpu.h
> index 218df7f4d3e1..5e45814bcc24 100644
> --- a/include/linux/cpu.h
> +++ b/include/linux/cpu.h
> @@ -189,4 +189,11 @@ static inline void cpu_smt_check_topology_early(void) { }
> static inline void cpu_smt_check_topology(void) { }
> #endif
>
> +/* generic cpu vulnerability attributes */
> +#define VULN_MELTDOWN 0x01
> +#define VULN_SPECTREV1 0x02
> +#define VULN_SPECTREV2 0x04
> +#define VULN_SSB 0x08
> +#define VULN_L1TF 0x10

nit: May use BIT() ?

Cheers
Suzuki

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