[Xen-devel] [PATCH v2 2/2] paravirt, xen: correct xen_nopvspin case

[Juergen Gross <jgross@xxxxxxxx>]

With the boot parameter "xen_nopvspin" specified a Xen guest should not
make use of paravirt spinlocks, but behave as if running on bare
metal. This is not true, however, as the qspinlock code will fall back
to a test-and-set scheme when it is detecting a hypervisor.

In order to avoid this disable the virt_spin_lock_key.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 arch/x86/xen/spinlock.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
index 25a7c4302ce7..e8ab80ad7a6f 100644
--- a/arch/x86/xen/spinlock.c
+++ b/arch/x86/xen/spinlock.c
@@ -10,6 +10,7 @@
 #include <linux/slab.h>
 
 #include <asm/paravirt.h>
+#include <asm/qspinlock.h>
 
 #include <xen/interface/xen.h>
 #include <xen/events.h>
@@ -129,6 +130,7 @@ void __init xen_init_spinlocks(void)
 
        if (!xen_pvspin) {
                printk(KERN_DEBUG "xen: PV spinlocks disabled\n");
+               static_branch_disable(&virt_spin_lock_key);
                return;
        }
        printk(KERN_DEBUG "xen: PV spinlocks enabled\n");
-- 
2.12.3


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