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

- From: Juergen Gross via Virtualization \<hidden\>
- Date: 2021-10-05 07:43:26 
- List: virtualization
- Page: https://ratatoskr.run/virtualization/2021/10/15818265
- Thread: https://ratatoskr.run/virtualization/2021/09/15818264/t.md

```text
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>


Juergen
```