From: lauraa@codeaurora.org (Laura Abbott)
To: linux-arm-kernel@lists.infradead.org
Subject: arm64 cache maintenance on read only address loops forever
Date: Tue, 25 Feb 2014 20:59:46 -0800 [thread overview]
Message-ID: <530D74C2.4000402@codeaurora.org> (raw)
Hi,
On arm64, set_pte_at currently write protects user ptes that are not
dirty. The expected behavior is that the fault handler will fix this up
on a write to the address. do_page_fault will not mark the fault as a
write though if ESR has the CM (cache maintenance) bit set. This has the
unfortunate side effect that if cache maintenance is performed on a user
address that has not yet been marked as dirty, handle_mm_fault may
return without actually adjusting the pte or returning an error. This
means that the fault will be infinitely retried.
Calling cache maintenance on an address that hasn't actually been
written to isn't all that useful but looping forever seems like a poor
result. It seems like the check in do_page_fault is too restrictive and
we need to be able to fault in pages via cache maintenance.
Thoughts?
Thanks,
Laura
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation
next reply other threads:[~2014-02-26 4:59 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-26 4:59 Laura Abbott [this message]
2014-02-26 13:55 ` arm64 cache maintenance on read only address loops forever Will Deacon
2014-02-26 21:40 ` Laura Abbott
2014-02-27 18:15 ` Will Deacon
2014-02-26 14:03 ` Catalin Marinas
2014-02-26 22:00 ` Laura Abbott
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