xen/x86/pvh: Use HVM's flush_tlb_others op

Using MMUEXT_TLB_FLUSH_MULTI doesn't buy us much since the hypervisor
will likely perform same IPIs as would have the guest.

More importantly, using MMUEXT_INVLPG_MULTI may not to invalidate the
guest's address on remote CPU (when, for example, VCPU from another guest
is running there).
Signed-off-by: NBoris Ostrovsky <boris.ostrovsky@oracle.com>
Suggested-by: NJan Beulich <jbeulich@suse.com>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>

arch/x86/xen/mmu.c

@@ -2495,14 +2495,9 @@ void __init xen_init_mmu_ops(void)
 {
 	x86_init.paging.pagetable_init = xen_pagetable_init;
 
-	/* Optimization - we can use the HVM one but it has no idea which
-	 * VCPUs are descheduled - which means that it will needlessly IPI
-	 * them. Xen knows so let it do the job.
-	 */
-	if (xen_feature(XENFEAT_auto_translated_physmap)) {
-		pv_mmu_ops.flush_tlb_others = xen_flush_tlb_others;
+	if (xen_feature(XENFEAT_auto_translated_physmap))
 		return;
-	}
+
 	pv_mmu_ops = xen_mmu_ops;
 
 	memset(dummy_mapping, 0xff, PAGE_SIZE);