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    Subject[PATCH 4.4 328/342] x86/irq: Check vector allocation early
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Thomas Gleixner <tglx@linutronix.de>

    commit 3716fd27a604d61a91cda47083504971486b80f1 upstream.

    __assign_irq_vector() uses the vector_cpumask which is assigned by
    apic->vector_allocation_domain() without doing basic sanity checks. That can
    result in a situation where the final assignement of a newly found vector
    fails in apic->cpu_mask_to_apicid_and(). So we have to do rollbacks for no
    reason.

    apic->cpu_mask_to_apicid_and() only fails if

    vector_cpumask & requested_cpumask & cpu_online_mask

    is empty.

    Check for this condition right away and if the result is empty try immediately
    the next possible cpu in the requested mask. So in case of a failure the old
    setting is unchanged and we can remove the rollback code.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Tested-by: Borislav Petkov <bp@alien8.de>
    Tested-by: Joe Lawrence <joe.lawrence@stratus.com>
    Cc: Jiang Liu <jiang.liu@linux.intel.com>
    Cc: Jeremiah Mahler <jmmahler@gmail.com>
    Cc: andy.shevchenko@gmail.com
    Cc: Guenter Roeck <linux@roeck-us.net>
    Link: http://lkml.kernel.org/r/20151231160106.561877324@linutronix.de
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/kernel/apic/vector.c | 38 +++++++++++++++++++++++++-------------
    1 file changed, 25 insertions(+), 13 deletions(-)

    --- a/arch/x86/kernel/apic/vector.c
    +++ b/arch/x86/kernel/apic/vector.c
    @@ -30,7 +30,7 @@ struct apic_chip_data {

    struct irq_domain *x86_vector_domain;
    static DEFINE_RAW_SPINLOCK(vector_lock);
    -static cpumask_var_t vector_cpumask, searched_cpumask;
    +static cpumask_var_t vector_cpumask, vector_searchmask, searched_cpumask;
    static struct irq_chip lapic_controller;
    #ifdef CONFIG_X86_IO_APIC
    static struct apic_chip_data *legacy_irq_data[NR_IRQS_LEGACY];
    @@ -128,8 +128,20 @@ static int __assign_irq_vector(int irq,
    while (cpu < nr_cpu_ids) {
    int new_cpu, vector, offset;

    + /* Get the possible target cpus for @mask/@cpu from the apic */
    apic->vector_allocation_domain(cpu, vector_cpumask, mask);

    + /*
    + * Clear the offline cpus from @vector_cpumask for searching
    + * and verify whether the result overlaps with @mask. If true,
    + * then the call to apic->cpu_mask_to_apicid_and() will
    + * succeed as well. If not, no point in trying to find a
    + * vector in this mask.
    + */
    + cpumask_and(vector_searchmask, vector_cpumask, cpu_online_mask);
    + if (!cpumask_intersects(vector_searchmask, mask))
    + goto next_cpu;
    +
    if (cpumask_subset(vector_cpumask, d->domain)) {
    if (cpumask_equal(vector_cpumask, d->domain))
    goto success;
    @@ -162,7 +174,7 @@ next:
    if (test_bit(vector, used_vectors))
    goto next;

    - for_each_cpu_and(new_cpu, vector_cpumask, cpu_online_mask) {
    + for_each_cpu(new_cpu, vector_searchmask) {
    if (!IS_ERR_OR_NULL(per_cpu(vector_irq, new_cpu)[vector]))
    goto next;
    }
    @@ -174,7 +186,7 @@ next:
    d->move_in_progress =
    cpumask_intersects(d->old_domain, cpu_online_mask);
    }
    - for_each_cpu_and(new_cpu, vector_cpumask, cpu_online_mask)
    + for_each_cpu(new_cpu, vector_searchmask)
    per_cpu(vector_irq, new_cpu)[vector] = irq_to_desc(irq);
    d->cfg.vector = vector;
    cpumask_copy(d->domain, vector_cpumask);
    @@ -196,8 +208,14 @@ next_cpu:
    return -ENOSPC;

    success:
    - /* cache destination APIC IDs into cfg->dest_apicid */
    - return apic->cpu_mask_to_apicid_and(mask, d->domain, &d->cfg.dest_apicid);
    + /*
    + * Cache destination APIC IDs into cfg->dest_apicid. This cannot fail
    + * as we already established, that mask & d->domain & cpu_online_mask
    + * is not empty.
    + */
    + BUG_ON(apic->cpu_mask_to_apicid_and(mask, d->domain,
    + &d->cfg.dest_apicid));
    + return 0;
    }

    static int assign_irq_vector(int irq, struct apic_chip_data *data,
    @@ -407,6 +425,7 @@ int __init arch_early_irq_init(void)
    arch_init_htirq_domain(x86_vector_domain);

    BUG_ON(!alloc_cpumask_var(&vector_cpumask, GFP_KERNEL));
    + BUG_ON(!alloc_cpumask_var(&vector_searchmask, GFP_KERNEL));
    BUG_ON(!alloc_cpumask_var(&searched_cpumask, GFP_KERNEL));

    return arch_early_ioapic_init();
    @@ -496,14 +515,7 @@ static int apic_set_affinity(struct irq_
    return -EINVAL;

    err = assign_irq_vector(irq, data, dest);
    - if (err) {
    - if (assign_irq_vector(irq, data,
    - irq_data_get_affinity_mask(irq_data)))
    - pr_err("Failed to recover vector for irq %d\n", irq);
    - return err;
    - }
    -
    - return IRQ_SET_MASK_OK;
    + return err ? err : IRQ_SET_MASK_OK;
    }

    static struct irq_chip lapic_controller = {
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