# Re: \[PATCH\] x86/paravirt: use %rip-relative addressing in hook calls

- From: Jan Beulich via Virtualization \<hidden\>
- Date: 2021-11-23 09:35:37 
- List: virtualization
- Page: https://ratatoskr.run/virtualization/2021/11/15818460
- Thread: https://ratatoskr.run/virtualization/2021/09/15818264/t.md

```text
On 05.10.2021 09:43, Juergen Gross wrote:
> On 30.09.21 14:40, Jan Beulich via Virtualization wrote:
>> While using a plain (constant) address works, its use needlessly invokes
>> a SIB addressing mode, making every call site one byte larger than
>> necessary. Instead of using an "i" constraint with address-of operator
>> and a 'c' operand modifier, simply use an ordinary "m" constraint, which
>> the 64-bit compiler will translate to %rip-relative addressing. This way
>> we also tell the compiler the truth about operand usage - the memory
>> location gets actually read, after all.
>>
>> 32-bit code generation is unaffected by the change.
>>
>> Signed-off-by: Jan Beulich <redacted>
> 
> Reviewed-by: Juergen Gross <jgross@suse.com>

Thanks. I notice this wasn't part of your 5.16-rc1 pull request, nor
did it make it into Linus'es tree via any other route. May I ask what
the plans here are?

Jan

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