linux-kernel - [PATCH 4.15 16/72] powerpc/mm: Workaround Nest MMU bug with TLB invalidations

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Date:   Fri,  6 Apr 2018 15:23:51 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Balbir Singh <bsingharora@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 4.15 16/72] powerpc/mm: Workaround Nest MMU bug with TLB invalidations

4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Benjamin Herrenschmidt <benh@...nel.crashing.org>

commit 80a4ae202f2d319eced8bbf612a4e8b0f11c21f5 upstream.

On POWER9 the Nest MMU may fail to invalidate some translations when
doing a tlbie "by PID" or "by LPID" that is targeted at the TLB only
and not the page walk cache.

This works around it by forcing such invalidations to escalate to
RIC=2 (full invalidation of TLB *and* PWC) when a coprocessor is in
use for the context.

Fixes: 03b8abedf4f4 ("cxl: Enable global TLBIs for cxl contexts")
Cc: stable@...r.kernel.org # v4.15+
Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Signed-off-by: Balbir Singh <bsingharora@...il.com>
[balbirs: fixed spelling and coding style to quiesce checkpatch.pl]
Tested-by: Balbir Singh <bsingharora@...il.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/mm/tlb-radix.c |   50 +++++++++++++++++++++++++++++++++++++-------
 1 file changed, 43 insertions(+), 7 deletions(-)

--- a/arch/powerpc/mm/tlb-radix.c
+++ b/arch/powerpc/mm/tlb-radix.c
@@ -85,7 +85,23 @@ static inline void _tlbiel_pid(unsigned
 static inline void _tlbie_pid(unsigned long pid, unsigned long ric)
 {
 	asm volatile("ptesync": : :"memory");
-	__tlbie_pid(pid, ric);
+
+	/*
+	 * Workaround the fact that the "ric" argument to __tlbie_pid
+	 * must be a compile-time contraint to match the "i" constraint
+	 * in the asm statement.
+	 */
+	switch (ric) {
+	case RIC_FLUSH_TLB:
+		__tlbie_pid(pid, RIC_FLUSH_TLB);
+		break;
+	case RIC_FLUSH_PWC:
+		__tlbie_pid(pid, RIC_FLUSH_PWC);
+		break;
+	case RIC_FLUSH_ALL:
+	default:
+		__tlbie_pid(pid, RIC_FLUSH_ALL);
+	}
 	asm volatile("eieio; tlbsync; ptesync": : :"memory");
 }
 
@@ -245,6 +261,16 @@ void radix__local_flush_tlb_page(struct
 }
 EXPORT_SYMBOL(radix__local_flush_tlb_page);
 
+static bool mm_needs_flush_escalation(struct mm_struct *mm)
+{
+	/*
+	 * P9 nest MMU has issues with the page walk cache
+	 * caching PTEs and not flushing them properly when
+	 * RIC = 0 for a PID/LPID invalidate
+	 */
+	return atomic_read(&mm->context.copros) != 0;
+}
+
 #ifdef CONFIG_SMP
 void radix__flush_tlb_mm(struct mm_struct *mm)
 {
@@ -255,9 +281,12 @@ void radix__flush_tlb_mm(struct mm_struc
 		return;
 
 	preempt_disable();
-	if (!mm_is_thread_local(mm))
-		_tlbie_pid(pid, RIC_FLUSH_TLB);
-	else
+	if (!mm_is_thread_local(mm)) {
+		if (mm_needs_flush_escalation(mm))
+			_tlbie_pid(pid, RIC_FLUSH_ALL);
+		else
+			_tlbie_pid(pid, RIC_FLUSH_TLB);
+	} else
 		_tlbiel_pid(pid, RIC_FLUSH_TLB);
 	preempt_enable();
 }
@@ -369,10 +398,14 @@ void radix__flush_tlb_range(struct vm_ar
 	}
 
 	if (full) {
-		if (local)
+		if (local) {
 			_tlbiel_pid(pid, RIC_FLUSH_TLB);
-		else
-			_tlbie_pid(pid, RIC_FLUSH_TLB);
+		} else {
+			if (mm_needs_flush_escalation(mm))
+				_tlbie_pid(pid, RIC_FLUSH_ALL);
+			else
+				_tlbie_pid(pid, RIC_FLUSH_TLB);
+		}
 	} else {
 		bool hflush = false;
 		unsigned long hstart, hend;
@@ -482,6 +515,9 @@ static inline void __radix__flush_tlb_ra
 	}
 
 	if (full) {
+		if (!local && mm_needs_flush_escalation(mm))
+			also_pwc = true;
+
 		if (local)
 			_tlbiel_pid(pid, also_pwc ? RIC_FLUSH_ALL : RIC_FLUSH_TLB);
 		else