powerpc/mm/radix: Flush page walk cache when freeing page table

Even though a tlb_flush() does a flush with invalidate all cache,
we can end up doing an RCU page table free before calling tlb_flush().
That means we can have page walk cache entries even after we free the
page table pages. This can result in us doing wrong page table walk.

Avoid this by doing pwc flush on every page table free. We can't batch
the pwc flush, because the rcu call back function where we free the
page table pages doesn't have information of the mmu gather. Thus we
have to do a pwc on every page table page freed.

Note: I also removed the dummy tlb_flush_pgtable call functions for
hash 32.

Fixes: 1a472c9dba6b ("powerpc/mm/radix: Add tlbflush routines")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 41 insertions, 0 deletions

diff --git a/arch/powerpc/mm/tlb-radix.c b/arch/powerpc/mm/tlb-radix.c
index 71083621884e..ab2f60e812e2 100644
--- a/arch/powerpc/mm/tlb-radix.c
+++ b/arch/powerpc/mm/tlb-radix.c
@@ -128,6 +128,21 @@ void radix__local_flush_tlb_mm(struct mm_struct *mm)
 }
 EXPORT_SYMBOL(radix__local_flush_tlb_mm);
 
+void radix__local_flush_tlb_pwc(struct mmu_gather *tlb, unsigned long addr)
+{
+	unsigned long pid;
+	struct mm_struct *mm = tlb->mm;
+
+	preempt_disable();
+
+	pid = mm->context.id;
+	if (pid != MMU_NO_CONTEXT)
+		_tlbiel_pid(pid, RIC_FLUSH_PWC);
+
+	preempt_enable();
+}
+EXPORT_SYMBOL(radix__local_flush_tlb_pwc);
+
 void radix___local_flush_tlb_page(struct mm_struct *mm, unsigned long vmaddr,
 			    unsigned long ap, int nid)
 {
@@ -183,6 +198,32 @@ no_context:
 }
 EXPORT_SYMBOL(radix__flush_tlb_mm);
 
+void radix__flush_tlb_pwc(struct mmu_gather *tlb, unsigned long addr)
+{
+	unsigned long pid;
+	struct mm_struct *mm = tlb->mm;
+
+	preempt_disable();
+
+	pid = mm->context.id;
+	if (unlikely(pid == MMU_NO_CONTEXT))
+		goto no_context;
+
+	if (!mm_is_core_local(mm)) {
+		int lock_tlbie = !mmu_has_feature(MMU_FTR_LOCKLESS_TLBIE);
+
+		if (lock_tlbie)
+			raw_spin_lock(&native_tlbie_lock);
+		_tlbie_pid(pid, RIC_FLUSH_PWC);
+		if (lock_tlbie)
+			raw_spin_unlock(&native_tlbie_lock);
+	} else
+		_tlbiel_pid(pid, RIC_FLUSH_PWC);
+no_context:
+	preempt_enable();
+}
+EXPORT_SYMBOL(radix__flush_tlb_pwc);
+
 void radix___flush_tlb_page(struct mm_struct *mm, unsigned long vmaddr,
 		       unsigned long ap, int nid)
 {