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Re: [PATCH 2/3] x86/clang: add retpoline support
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 16 Feb 2022 15:07:51 +0100
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Wed, 16 Feb 2022 14:08:01 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 16.02.2022 12:26, Roger Pau Monné wrote:
> On Wed, Feb 16, 2022 at 10:47:52AM +0100, Jan Beulich wrote:
>> On 16.02.2022 10:02, Roger Pau Monne wrote:
>>> Detect whether the compiler supports clang retpoline option and enable
>>> by default if available, just like it's done for gcc.
>>>
>>> Note clang already disables jump tables when retpoline is enabled, so
>>> there's no need to also pass the fno-jump-tables parameter.
>>
>> That's one of the secondary gcc side arrangements. What about the other
>> (-mindirect-branch-register)?
>
> clang already passes the return address on a register always on amd64
> so that's not needed either. I can add a comment like I've done for
> no-jump-tables.
>
>>> Reported-by: Jan Beulich <JBeulich@xxxxxxxx>
>>
>> That's Andrew, not me?
>
> Ops, sorry, I got that mixed up then.
With the adjustments then
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
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