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Re: [PATCH 1/2] xen/*/nospec: Provide common versions of evaluate_nospec/block_speculation


  • To: Jan Beulich <jbeulich@xxxxxxxx>, Oleksii <oleksii.kurochko@xxxxxxxxx>
  • From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • Date: Tue, 5 Mar 2024 15:47:13 +0000
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  • Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Shawn Anastasio <sanastasio@xxxxxxxxxxxxxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Julien Grall <julien@xxxxxxx>
  • Delivery-date: Tue, 05 Mar 2024 15:47:22 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 05/03/2024 3:43 pm, Jan Beulich wrote:
> On 05.03.2024 16:15, Oleksii wrote:
>> I agree that upon examining the current state of the code around these
>> functions, it appears safe to provide stubs. However, the reason my
>> patch was rejected is that it may not be entirely safe, as Julien
>> pointed out that even with Arm, some functions shouldn't be empty.
>>
>> What I would like to propose is that it might be beneficial, at least
>> in CONFIG_DEBUG=y, to have a warning message. Does that make sense?
> A warning message to what effect? And are you thinking of a build-time
> warning, or a runtime one? Plus wouldn't different aspects quickly lead
> to proliferation of warnings?

Putting in a warning for something like this is specifically a bad idea.

All it will do is cause people to ignore warnings, and that's the very
worst thing Xen could do.

~Andrew



 


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