x86/mm/cpa: Flush direct map alias during cpa

As an optimization, cpa_flush() was changed to optionally only flush
the range in @cpa if it was small enough.  However, this range does
not include any direct map aliases changed in cpa_process_alias(). So
small set_memory_() calls that touch that alias don't get the direct
map changes flushed. This situation can happen when the virtual
address taking variants are passed an address in vmalloc or modules
space.

In these cases, force a full TLB flush.

Note this issue does not extend to cases where the set_memory_() calls are
passed a direct map address, or page array, etc, as the primary target. In
those cases the direct map would be flushed.

Fixes: 935f5839 ("x86/mm/cpa: Optimize cpa_flush_array() TLB invalidation")
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200424105343.GA20730@hirez.programming.kicks-ass.net

arch/x86/mm/pat/set_memory.c

@@ -43,7 +43,8 @@ struct cpa_data {
 	unsigned long	pfn;
 	unsigned int	flags;
 	unsigned int	force_split		: 1,
-			force_static_prot	: 1;
+			force_static_prot	: 1,
+			force_flush_all		: 1;
 	struct page	**pages;
 };
 
@@ -355,10 +356,10 @@ static void cpa_flush(struct cpa_data *data, int cache)
 		return;
 	}
 
-	if (cpa->numpages <= tlb_single_page_flush_ceiling)
-		on_each_cpu(__cpa_flush_tlb, cpa, 1);
-	else
+	if (cpa->force_flush_all || cpa->numpages > tlb_single_page_flush_ceiling)
 		flush_tlb_all();
+	else
+		on_each_cpu(__cpa_flush_tlb, cpa, 1);
 
 	if (!cache)
 		return;
@@ -1598,6 +1599,8 @@ static int cpa_process_alias(struct cpa_data *cpa)
 		alias_cpa.flags &= ~(CPA_PAGES_ARRAY | CPA_ARRAY);
 		alias_cpa.curpage = 0;
 
+		cpa->force_flush_all = 1;
+
 		ret = __change_page_attr_set_clr(&alias_cpa, 0);
 		if (ret)
 			return ret;
@@ -1618,6 +1621,7 @@ static int cpa_process_alias(struct cpa_data *cpa)
 		alias_cpa.flags &= ~(CPA_PAGES_ARRAY | CPA_ARRAY);
 		alias_cpa.curpage = 0;
 
+		cpa->force_flush_all = 1;
 		/*
 		 * The high mapping range is imprecise, so ignore the
 		 * return value.