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Subject[PATCH v3 2/2] paravirt,xen: correct xen_nopvspin case
Date
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@suse.com>
---
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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