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Re: [PATCH 2/2] x86/time: add CF-clobber annotations


  • To: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Tue, 1 Mar 2022 15:18:26 +0100
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  • Cc: Wei Liu <wl@xxxxxxx>, Roger Pau Monne <roger.pau@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Tue, 01 Mar 2022 14:18:44 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 01.03.2022 14:18, Andrew Cooper wrote:
> On 01/03/2022 11:06, Jan Beulich wrote:
>> With bed9ae54df44 ("x86/time: switch platform timer hooks to altcall")
>> in place we can further arrange for ENDBR removal from the functions no
>> longer subject to indirect calls. Note that plt_tsc is left untouched,
>> for not holding any pointer eligible for ENDBR removal.
> 
> I'd be tempted to include it, for consistency sake alone.
> 
> It is less likely to go wrong in the future if another hook is introduced.

Can do, sure.

>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> With the commit message, I'm not not certain if this is linked to the
> previous patch.
> 
> Overall it looks fine, but I'd like to get clarity on this point.

Converting read_tsc() was discussed (with Roger) earlier on, so I'd
view this as a separate change. As said in reply to your comments on
the 1st patch, how exactly read_tsc() looks like is orthogonal to
the changes here at least as long as it doesn't live in .text.

Jan




 


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