openwrt/target/linux/generic/pending-5.15/301-MIPS-Add-barriers-between-dcache-icache-flushes.patch

From e6e6ef4275978823ec3a84133fc91f4ffbef5c84 Mon Sep 17 00:00:00 2001
From: Paul Burton <[email protected]>
Date: Mon, 22 Feb 2016 18:09:44 +0000
Subject: [PATCH] MIPS: Add barriers between dcache & icache flushes

Index-based cache operations may be arbitrarily reordered by out of
order CPUs. Thus code which writes back the dcache & then invalidates
the icache using indexed cache ops must include a barrier between
operating on the 2 caches in order to prevent the scenario in which:

  - icache invalidation occurs.

  - icache fetch occurs, due to speculation.

  - dcache writeback occurs.

If the above were allowed to happen then the icache would contain stale
data. Forcing the dcache writeback to complete before the icache
invalidation avoids this.

Signed-off-by: Paul Burton <[email protected]>
Cc: James Hogan <[email protected]>
---
 arch/mips/mm/c-r4k.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

--- a/arch/mips/mm/c-r4k.c
+++ b/arch/mips/mm/c-r4k.c
@@ -515,6 +515,7 @@ static inline void local_r4k___flush_cac
 
 	default:
 		r4k_blast_dcache();
+		mb(); /* cache instructions may be reordered */
 		r4k_blast_icache();
 		break;
 	}
@@ -595,8 +596,10 @@ static inline void local_r4k_flush_cache
 	if (cpu_has_dc_aliases || (exec && !cpu_has_ic_fills_f_dc))
 		r4k_blast_dcache();
 	/* If executable, blast stale lines from icache */
-	if (exec)
+	if (exec) {
+		mb(); /* cache instructions may be reordered */
 		r4k_blast_icache();
+	}
 }
 
 static void r4k_flush_cache_range(struct vm_area_struct *vma,
@@ -697,8 +700,13 @@ static inline void local_r4k_flush_cache
 	if (cpu_has_dc_aliases || (exec && !cpu_has_ic_fills_f_dc)) {
 		vaddr ? r4k_blast_dcache_page(addr) :
 			r4k_blast_dcache_user_page(addr);
-		if (exec && !cpu_icache_snoops_remote_store)
+		if (exec)
+			mb(); /* cache instructions may be reordered */
+
+		if (exec && !cpu_icache_snoops_remote_store) {
 			r4k_blast_scache_page(addr);
+			mb(); /* cache instructions may be reordered */
+		}
 	}
 	if (exec) {
 		if (vaddr && cpu_has_vtag_icache && mm == current->active_mm) {
@@ -765,6 +773,7 @@ static inline void __local_r4k_flush_ica
 			else
 				blast_dcache_range(start, end);
 		}
+		mb(); /* cache instructions may be reordered */
 	}
 
 	if (type == R4K_INDEX ||