[PATCH 6/6] xen: add xen_pin_vcpu() to support calling functions on a dedicated pcpu

From: Juergen Gross
Date: Fri Mar 11 2016 - 07:00:31 EST


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@xxxxxxxx>
---
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 d09e4c9..325e108 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1884,6 +1884,45 @@ 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);
+ if (cpu < 0)
+ return;
+
+ switch (ret) {
+ case -ENOSYS:
+ pr_warn("The kernel tried to call a function on physical cpu %d, but Xen isn't\n"
+ "supporting this. In case of problems you might 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("The kernel tried to call a function on physical cpu %d, but this cpu\n"
+ "seems not to be available. Please check your 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,
@@ -1892,6 +1931,7 @@ 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);

--
2.6.2