lkml.org 
[lkml]   [2017]   [Oct]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip:locking/core] locking/spinlocks, paravirt, xen: Correct the xen_nopvspin case
Commit-ID:  e6fd28eb3522b31f79a938e24674f77268a120fd
Gitweb: https://git.kernel.org/tip/e6fd28eb3522b31f79a938e24674f77268a120fd
Author: Juergen Gross <jgross@suse.com>
AuthorDate: Wed, 6 Sep 2017 19:36:25 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 10 Oct 2017 11:50:13 +0200

locking/spinlocks, paravirt, xen: Correct the xen_nopvspin case

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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Waiman Long <longman@redhat.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: jeremy@goop.org
Cc: rusty@rustcorp.com.au
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/20170906173625.18158-3-jgross@suse.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
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 25a7c43..e8ab80a 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");
\
 
 \ /
  Last update: 2017-10-10 13:08    [W:0.152 / U:0.184 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site