| Message ID | 20170906152928.8658-3-jgross@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 09/06/2017 11:29 AM, Juergen Gross wrote: > 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"); Acked-by: Waiman Long <longman@redhat.com>
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");
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(+)