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    Subject[PATCH v6 4/6] xen: add xen_pin_vcpu() to support calling functions on a dedicated pcpu
    Date
    Some hardware models (e.g. Dell Studio 1555 laptops) require calls to
    the firmware to be issued on cpu 0 only. As Dom0 might have to use
    these calls, add xen_pin_vcpu() to achieve this functionality.

    In case either the domain doesn't have the privilege to make the
    related hypercall or the hypervisor isn't supporting it, issue a
    warning once and disable further pinning attempts.

    Signed-off-by: Juergen Gross <jgross@suse.com>
    Acked-by: David Vrabel <david.vrabel@citrix.com>
    ---
    V5: less wordy messages as requested by David Vrabel
    ---
    arch/x86/xen/enlighten.c | 40 ++++++++++++++++++++++++++++++++++++++++
    1 file changed, 40 insertions(+)

    diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
    index b86ebb1..bc9aaba 100644
    --- a/arch/x86/xen/enlighten.c
    +++ b/arch/x86/xen/enlighten.c
    @@ -1925,6 +1925,45 @@ static void xen_set_cpu_features(struct cpuinfo_x86 *c)
    }
    }

    +static void xen_pin_vcpu(int cpu)
    +{
    + static bool disable_pinning;
    + struct sched_pin_override pin_override;
    + int ret;
    +
    + if (disable_pinning)
    + return;
    +
    + pin_override.pcpu = cpu;
    + ret = HYPERVISOR_sched_op(SCHEDOP_pin_override, &pin_override);
    +
    + /* Ignore errors when removing override. */
    + if (cpu < 0)
    + return;
    +
    + switch (ret) {
    + case -ENOSYS:
    + pr_warn("Unable to pin on physical cpu %d. In case of problems consider vcpu pinning.\n",
    + cpu);
    + disable_pinning = true;
    + break;
    + case -EPERM:
    + WARN(1, "Trying to pin vcpu without having privilege to do so\n");
    + disable_pinning = true;
    + break;
    + case -EINVAL:
    + case -EBUSY:
    + pr_warn("Physical cpu %d not available for pinning. Check Xen cpu configuration.\n",
    + cpu);
    + break;
    + case 0:
    + break;
    + default:
    + WARN(1, "rc %d while trying to pin vcpu\n", ret);
    + disable_pinning = true;
    + }
    +}
    +
    const struct hypervisor_x86 x86_hyper_xen = {
    .name = "Xen",
    .detect = xen_platform,
    @@ -1933,6 +1972,7 @@ const struct hypervisor_x86 x86_hyper_xen = {
    #endif
    .x2apic_available = xen_x2apic_para_available,
    .set_cpu_features = xen_set_cpu_features,
    + .pin_vcpu = xen_pin_vcpu,
    };
    EXPORT_SYMBOL(x86_hyper_xen);

    --
    2.6.6
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