xen: Add xen_pin_vcpu() to support calling functions on a dedicated pCPU

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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: David Vrabel <david.vrabel@citrix.com>
Cc: Douglas_Warzecha@dell.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akataria@vmware.com
Cc: boris.ostrovsky@oracle.com
Cc: chrisw@sous-sol.org
Cc: hpa@zytor.com
Cc: jdelvare@suse.com
Cc: jeremy@goop.org
Cc: linux@roeck-us.net
Cc: pali.rohar@gmail.com
Cc: rusty@rustcorp.com.au
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1472453327-19050-5-git-send-email-jgross@suse.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 40 insertions, 0 deletions

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index b86ebb1a9a7f..bc9aaba01a22 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);