lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Thu, 28 Dec 2006 01:00:00 +0100
From:	Martin Schwidefsky <>
To:	Linus Torvalds <>
Cc:	Peter Zijlstra <>,
	Martin Michlmayr <>,
	Hugh Dickins <>,
	Nick Piggin <>,
	Arjan van de Ven <>,
	Andrei Popa <>,
	Andrew Morton <>,
	Linux Kernel Mailing List <>,
	Florian Weimer <>,
	Marc Haber <>,
	Heiko Carstens <>,
	Arnd Bergmann <>,
Subject: Re: [PATCH] mm: fix page_mkclean_one (was: 2.6.19 file content
	corruption on ext3)

On Thu, 2006-12-21 at 12:01 -0800, Linus Torvalds wrote:
> What do you guys think? Does something like this work out for S/390 too? I
> tried to make that "ptep_flush_dirty()" concept work for architectures
> that hide the dirty bit somewhere else too, but..

For s390 there are two aspects to consider:
1) the pte values are 100% software controlled. They only change because
a cpu stored a value to it or issued one of the specialized instructions
(csp, ipte and idte). The ptep_flush_dirty would be a nop for s390.
2) ptep_exchange is a bit dangerous. For s390 we need a lock that
protects the software controlled updates of the ptes. The reason is the
ipte instruction. It is implemented by the machine microcode in a
non-atomic way in regard to the memory. It reads the byte of the pte
that contains the invalid bit, flushes the tlb entries for it and then
writes back the byte with the invalid bit set. The microcode makes sure
that this pte cannot be used for form a new tlb on any cpu while the
ipte is in progress.
That means a compare-and-swap semantics on ptes won't work together with
the ipte optimization. As long as there is the pte lock that protects
all software accesses to the pte we are fine. But if any code expects
that ptep_exchange does something like an xchg things break.

blue skies,

Martin Schwidefsky
Linux for zSeries Development & Services
IBM Deutschland Entwicklung GmbH

"Reality continues to ruin my life." - Calvin.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

Powered by blists - more mailing lists