x86: cpa: implement clflush optimization

Use clflush on CPUs which support this.

clflush is only used when the page attribute operation has been
successful. On CPUs which do not support clflush and in the case of
error the old fashioned global_flush_tlb() is called.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/mm/pageattr.c

@@ -52,6 +52,37 @@ static void global_flush_tlb(void)
 	on_each_cpu(flush_kernel_map, NULL, 1, 1);
 }
 
+struct clflush_data {
+	unsigned long addr;
+	int numpages;
+};
+
+static void __cpa_flush_range(void *arg)
+{
+	struct clflush_data *cld = arg;
+
+	/*
+	 * We could optimize that further and do individual per page
+	 * tlb invalidates for a low number of pages. Caveat: we must
+	 * flush the high aliases on 64bit as well.
+	 */
+	__flush_tlb_all();
+
+	clflush_cache_range((void *) cld->addr, cld->numpages * PAGE_SIZE);
+}
+
+static void cpa_flush_range(unsigned long addr, int numpages)
+{
+	struct clflush_data cld;
+
+	BUG_ON(irqs_disabled());
+
+	cld.addr = addr;
+	cld.numpages = numpages;
+
+	on_each_cpu(__cpa_flush_range, &cld, 1, 1);
+}
+
 /*
  * Certain areas of memory on x86 require very specific protection flags,
  * for example the BIOS area or kernel text. Callers don't always get this
@@ -316,7 +347,16 @@ static int change_page_attr_set_clr(unsigned long addr, int numpages,
 	int ret = __change_page_attr_set_clr(addr, numpages, mask_set,
 					     mask_clr);
 
-	global_flush_tlb();
+	/*
+	 * On success we use clflush, when the CPU supports it to
+	 * avoid the wbindv. If the CPU does not support it and in the
+	 * error case we fall back to global_flush_tlb (which uses
+	 * wbindv):
+	 */
+	if (!ret && cpu_has_clflush)
+		cpa_flush_range(addr, numpages);
+	else
+		global_flush_tlb();
 
 	return ret;
 }