Subject: [PATCH 3/4] powerpc/mm/radix: Avoid flushing the PWC on every flush_tlb_range

From: Benjamin Herrenschmidt <[email-masked]>
Date: Fri, 14 Jul 2017 11:52:57 +1000

We do that because it's used by THP pmd collapsing, so use
instead a dedicated flush function.

Signed-off-by: Benjamin Herrenschmidt <[email-masked]>
---
 .../powerpc/include/asm/book3s/64/tlbflush-radix.h |  1 +
 arch/powerpc/mm/pgtable-radix.c                    |  5 ++-
 arch/powerpc/mm/tlb-radix.c                        | 41 +++++++++++++++++++---
 3 files changed, 41 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/tlbflush-radix.h b/arch/powerpc/include/asm/book3s/64/tlbflush-radix.h
index 7196999..9b433a6 100644
--- a/arch/powerpc/include/asm/book3s/64/tlbflush-radix.h
+++ b/arch/powerpc/include/asm/book3s/64/tlbflush-radix.h
@@ -36,6 +36,7 @@ extern void radix__flush_tlb_page_psize(struct mm_struct *mm, unsigned long vmad
 #define radix__flush_tlb_page_psize(mm,addr,p) radix__local_flush_tlb_page_psize(mm,addr,p)
 #endif
 extern void radix__flush_tlb_pwc(struct mmu_gather *tlb, unsigned long addr);
+extern void radix__flush_tlb_collapsed_pmd(struct mm_struct *mm, unsigned long addr);
 extern void radix__flush_tlb_lpid_va(unsigned long lpid, unsigned long gpa,
 				     unsigned long page_size);
 extern void radix__flush_tlb_lpid(unsigned long lpid);
diff --git a/arch/powerpc/mm/pgtable-radix.c b/arch/powerpc/mm/pgtable-radix.c
index c28165d..83d70f7 100644
--- a/arch/powerpc/mm/pgtable-radix.c
+++ b/arch/powerpc/mm/pgtable-radix.c
@@ -706,9 +706,12 @@ pmd_t radix__pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long addre
 	 */
 	pmd = *pmdp;
 	pmd_clear(pmdp);
+
 	/*FIXME!!  Verify whether we need this kick below */
 	kick_all_cpus_sync();
-	flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
+
+	radix__flush_tlb_collapsed_pmd(vma->vm_mm, address);
+
 	return pmd;
 }
 
diff --git a/arch/powerpc/mm/tlb-radix.c b/arch/powerpc/mm/tlb-radix.c
index f65c928..73d3fbf 100644
--- a/arch/powerpc/mm/tlb-radix.c
+++ b/arch/powerpc/mm/tlb-radix.c
@@ -267,11 +267,7 @@ void radix__flush_tlb_range(struct vm_area_struct *vma, unsigned long start,
 {
 	struct mm_struct *mm = vma->vm_mm;
 
-	/*
-	 * This is currently used when collapsing THPs so we need to
-	 * flush the PWC. We should fix this.
-	 */
-	radix__flush_all_mm(mm);
+	radix__flush_tlb_mm(mm);
 }
 EXPORT_SYMBOL(radix__flush_tlb_range);
 
@@ -350,6 +346,41 @@ void radix__flush_tlb_range_psize(struct mm_struct *mm, unsigned long start,
 	preempt_enable();
 }
 
+void radix__flush_tlb_collapsed_pmd(struct mm_struct *mm, unsigned long addr)
+{
+	int local = mm_is_thread_local(mm);
+	unsigned long ap = mmu_get_ap(mmu_virtual_psize);
+	unsigned long pid, end;
+
+
+	pid = mm ? mm->context.id : 0;
+	if (unlikely(pid == MMU_NO_CONTEXT))
+		goto no_context;
+
+	/* 4k page size, just blow the world */
+	if (PAGE_SIZE == 0x1000) {
+		radix__flush_all_mm(mm);
+		return;
+	}
+
+	/* Otherwise first do the PWC */
+	if (local)
+		_tlbiel_pid(pid, RIC_FLUSH_PWC);
+	else
+		_tlbie_pid(pid, RIC_FLUSH_PWC);
+
+	/* Then iterate the pages */
+	end = addr + HPAGE_PMD_SIZE;
+	for (; addr < end; addr += PAGE_SIZE) {
+		if (local)
+			_tlbiel_va(addr, pid, ap, RIC_FLUSH_TLB);
+		else
+			_tlbie_va(addr, pid, ap, RIC_FLUSH_TLB);
+	}
+no_context:
+	preempt_enable();
+}
+
 void radix__flush_tlb_lpid_va(unsigned long lpid, unsigned long gpa,
 			      unsigned long page_size)
 {
-- 
2.9.4