Re: [Xen-devel] [PATCH] x86/entry/64: Remove %ebx handling from error_entry/exit

[Andy Lutomirski <luto@xxxxxxxxxx>]

On Thu, Aug 16, 2018 at 8:19 AM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> On Fri, Aug 10, 2018 at 12:23:45AM -0700, Sarah Newman wrote:
>> On 08/09/2018 05:41 AM, David Woodhouse wrote:
>> > On Wed, 2018-08-08 at 10:35 -0700, Sarah Newman wrote:
>> >> commit b3681dd548d06deb2e1573890829dff4b15abf46 upstream.
>> >>
>> >> This version applies to v4.9.
>> >
>> > I think you can kill the 'xorl %ebx,%ebx' from error_entry too but yes,
>> > this does want to go to 4.9 and earlier because the 'Fixes:' tag is a
>> > bit of a lie — the problem existed before that, at least in theory.
>>
>> The commit 2140a9942 "x86/entry/64: Relax pvops stub clobber
>> specifications" was what removed the "movl %ebx, %eax" line later on
>> originally, but it was the commit 3ac6d8c787b8 that removed the
>> 'xorl %ebx,%ebx'. So these weren't matched.
>>
>> I don't know if it's a concern, but if someone had gone to the effort of
>> backporting the original commit 3ac6d8c787b83, adding the removal of
>> 'xorl %ebx,%ebx' to this patch would create merge conflicts.
>> For that reason and given the line is harmless, should it be left in?
>
> I need some kind of agreement here for me to know what to do with this
> patch...  {hint}
>

I would remove the xorl.

If there's an actual candidate patch, I'd be happy to read it.

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