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parisc: Fix flush_anon_page on PA8800/PA8900

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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@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>
Cc: stable@vger.kernel.org   # v5.18+
This commit is contained in:
John David Anglin 2022-06-18 15:14:34 +00:00 committed by Helge Deller
parent d16c5c7c92
commit e9ed22e6e5
1 changed files with 4 additions and 1 deletions
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5
arch/parisc/kernel/cache.c
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@ -722,7 +722,10 @@ void flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned lon
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;
}