linux-kernel - [PATCH 5.18 154/181] parisc: Fix flush_anon

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Date:   Mon, 27 Jun 2022 13:22:07 +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, John David Anglin <dave.anglin@...l.net>,
        Helge Deller <deller@....de>
Subject: [PATCH 5.18 154/181] parisc: Fix flush_anon_page on PA8800/PA8900

From: John David Anglin <dave.anglin@...l.net>

commit e9ed22e6e5010997a2f922eef61ca797d0a2a246 upstream.

Anonymous pages are allocated with the shared mappings colouring,
SHM_COLOUR. Since the alias boundary on machines with PA8800 and
PA8900 processors is unknown, flush_user_cache_page() might not
flush all mappings of a shared anonymous page. Flushing the whole
data cache flushes all mappings.

This won't fix all coherency issues with shared mappings but it
seems to work well in practice.  I haven't seen any random memory
faults in almost a month on a rp3440 running as a debian buildd
machine.

There is a small preformance hit.

Signed-off-by: John David Anglin <dave.anglin@...l.net>
Signed-off-by: Helge Deller <deller@....de>
Cc: stable@...r.kernel.org   # v5.18+
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/parisc/kernel/cache.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/arch/parisc/kernel/cache.c
+++ b/arch/parisc/kernel/cache.c
@@ -722,7 +722,10 @@ void flush_anon_page(struct vm_area_stru
 		return;

 	if (parisc_requires_coherency()) {
-		flush_user_cache_page(vma, vmaddr);
+		if (vma->vm_flags & VM_SHARED)
+			flush_data_cache();
+		else
+			flush_user_cache_page(vma, vmaddr);
 		return;
 	}