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    Subject[PATCH v3 1/7] sysfs/cpu: Allow individual architectures to select vulnerabilities
    Date
    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;
    +
    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
    +
    #endif /* _LINUX_CPU_H_ */
    --
    2.17.2
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