[PATCH 20 of 24] xen: disable preemption during tlb flush

[Jeremy Fitzhardinge <jeremy@goop.org>]

Various places in the kernel flush the tlb even though preemption doens't
guarantee the tlb flush is happening on any particular CPU.  In many cases
this doesn't seem to matter, so don't make a fuss about it.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
---
 arch/x86/xen/enlighten.c |   15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -532,26 +532,37 @@
 static void xen_flush_tlb(void)
 {
 	struct mmuext_op *op;
-	struct multicall_space mcs = xen_mc_entry(sizeof(*op));
+	struct multicall_space mcs;
+
+	preempt_disable();
+
+	mcs = xen_mc_entry(sizeof(*op));
 
 	op = mcs.args;
 	op->cmd = MMUEXT_TLB_FLUSH_LOCAL;
 	MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF);
 
 	xen_mc_issue(PARAVIRT_LAZY_MMU);
+
+	preempt_enable();
 }
 
 static void xen_flush_tlb_single(unsigned long addr)
 {
 	struct mmuext_op *op;
-	struct multicall_space mcs = xen_mc_entry(sizeof(*op));
+	struct multicall_space mcs;
 
+	preempt_disable();
+
+	mcs = xen_mc_entry(sizeof(*op));
 	op = mcs.args;
 	op->cmd = MMUEXT_INVLPG_LOCAL;
 	op->arg1.linear_addr = addr & PAGE_MASK;
 	MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF);
 
 	xen_mc_issue(PARAVIRT_LAZY_MMU);
+
+	preempt_enable();
 }
 
 static void xen_flush_tlb_others(const cpumask_t *cpus, struct mm_struct *mm,