Virtualization - Jun 2023 - [PATCH RFC 13/43] x86/paravirt: Use relative reference for original instruction

On 28.04.23 11:50, Hou Wenlong wrote:
> Similar to the alternative patching, use relative reference for original
> instruction rather than absolute one, which saves 8 bytes for one entry
> on x86_64.  And it could generate R_X86_64_PC32 relocation instead of
> R_X86_64_64 relocation, which also reduces relocation metadata on
> relocatable builds. And the alignment could be hard coded to be 4 now.
> 
> Signed-off-by: Hou Wenlong <houwenlong.hwl at antgroup.com>
> Cc: Thomas Garnier <thgarnie at chromium.org>
> Cc: Lai Jiangshan <jiangshan.ljs at antgroup.com>
> Cc: Kees Cook <keescook at chromium.org>
Reviewed-by: Juergen Gross <jgross at suse.com>

I think this patch should be taken even without the series.


Juergen
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> On Jun 1, 2023, at 2:29 AM, Juergen Gross <jgross at suse.com> wrote:
> 
> On 28.04.23 11:50, Hou Wenlong wrote:
>> Similar to the alternative patching, use relative reference for
original
>> instruction rather than absolute one, which saves 8 bytes for one entry
>> on x86_64.  And it could generate R_X86_64_PC32 relocation instead of
>> R_X86_64_64 relocation, which also reduces relocation metadata on
>> relocatable builds. And the alignment could be hard coded to be 4 now.
>> Signed-off-by: Hou Wenlong <houwenlong.hwl at antgroup.com>
>> Cc: Thomas Garnier <thgarnie at chromium.org>
>> Cc: Lai Jiangshan <jiangshan.ljs at antgroup.com>
>> Cc: Kees Cook <keescook at chromium.org>
> 
> Reviewed-by: Juergen Gross <jgross at suse.com>
> 
> I think this patch should be taken even without the series.
It looks good to me, I am just not sure what the alignment is needed
at all.

Why not to make the struct __packed (like struct alt_instr) and get rid
of all the .align directives? Am I missing something?