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Re: [PATCH v4 2/4] xen: Add files needed for minimal ppc64le build
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 19 Jun 2023 10:02:55 +0200
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- Cc: tpearson@xxxxxxxxxxxxxxxxxxxxx, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Shawn Anastasio <sanastasio@xxxxxxxxxxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Mon, 19 Jun 2023 08:02:59 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 16.06.2023 22:27, Andrew Cooper wrote:
> On 16/06/2023 6:48 pm, Shawn Anastasio wrote:
>> diff --git a/xen/arch/ppc/ppc64/head.S b/xen/arch/ppc/ppc64/head.S
>> new file mode 100644
>> index 0000000000..0b289c713a
>> --- /dev/null
>> +++ b/xen/arch/ppc/ppc64/head.S
>> @@ -0,0 +1,27 @@
>> +/* SPDX-License-Identifier: GPL-2.0-or-later */
>> +
>> +.section .text.header, "ax", %progbits
>> +
>> +ENTRY(start)
>> + /*
>> + * Depending on how we were booted, the CPU could be running in either
>> + * Little Endian or Big Endian mode. The following trampoline from Linux
>> + * cleverly uses an instruction that encodes to a NOP if the CPU's
>> + * endianness matches the assumption of the assembler (LE, in our case)
>> + * or a branch to code that performs the endian switch in the other
>> case.
>> + */
>
> Sorry, I also meant to ask. How prevalent is Big Endian in practice in
> the Power world?
>
> It's another area (like 4k pages) where I expect there to be plenty of
> fun to be had with the codebase.
Why? I'd expect "fun" if ppc was meaning to run in big-endian mode.
Jan
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