From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: "Tyrel Datwyler" <tyreld@linux.vnet.ibm.com>,
"Michal Suchánek" <msuchanek@suse.de>,
"Ashley Lai" <ashleydlai@gmail.com>,
"Paul Mackerras" <paulus@samba.org>,
"Michael Ellerman" <mpe@ellerman.id.au>,
"Peter Huewe" <peterhuewe@gmx.de>,
"Marcel Selhorst" <tpmdd@selhorst.net>,
"Jarkko Sakkinen" <jarkko.sakkinen@linux.intel.com>,
"Jason Gunthorpe" <jgunthorpe@obsidianresearch.com>,
tpmdd-devel@lists.sourceforge.net, linuxppc-dev@lists.ozlabs.org,
linux-kernel@vger.kernel.org
Subject: Re: ibmvtpm byteswapping inconsistency
Date: Sat, 28 Jan 2017 06:58:57 +1100 [thread overview]
Message-ID: <1485547137.2980.94.camel@kernel.crashing.org> (raw)
In-Reply-To: <e518682f-e563-9533-9ffd-f465c662e998@linux.vnet.ibm.com>
On Fri, 2017-01-27 at 10:02 -0800, Tyrel Datwyler wrote:
> > The problem is that we are packing an in-memory structure into 2
> > registers and it's expected that this structure is laid out in the
> > registers as if it had been loaded by a BE CPU.
>
> This is only the case if the cpu is BE. If the cpu is LE, regardless of
> the fact that our in memory structure is laid out BE, when we break it
> into 2 words each of those words needs to be loaded LE.
That doesn't make sense and doesn't match the code... The structure
needs to always have the same in-register layout regardless of the
endianness of the CPU, especially since the underlying hypervisor
will most likely be BE :-)
Thta's why the code does a be64_to_cpu() when loading it, this in
effect performs a "BE" load, which on a BE CPU is just a normal load
and on LE is a swap to compensate for the CPU loading it the "wrong way
around".
Cheers,
Ben.
next prev parent reply other threads:[~2017-01-27 20:44 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-26 20:22 ibmvtpm byteswapping inconsistency Michal Suchánek
2017-01-26 22:05 ` Jason Gunthorpe
2017-01-26 22:43 ` Michal Suchanek
2017-01-26 22:58 ` Ashley Lai
2017-02-02 4:40 ` Vicky
2017-02-02 10:55 ` Michael Ellerman
2017-02-02 11:29 ` Michal Suchánek
2017-02-02 15:17 ` David Laight
2017-01-27 1:42 ` Tyrel Datwyler
2017-01-27 1:50 ` Benjamin Herrenschmidt
2017-01-27 9:03 ` Michal Suchanek
2017-01-27 21:19 ` Tyrel Datwyler
2017-01-30 4:32 ` Michael Ellerman
2017-01-30 20:34 ` Tyrel Datwyler
2017-01-31 8:38 ` Michael Ellerman
2017-01-27 18:02 ` Tyrel Datwyler
2017-01-27 19:58 ` Benjamin Herrenschmidt [this message]
2017-01-27 20:32 ` Tyrel Datwyler
2017-01-28 0:35 ` msuchanek
2017-01-28 4:28 ` Benjamin Herrenschmidt
2017-01-30 14:42 ` David Laight
2017-01-27 11:18 ` David Laight
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