[PATCHv11 05/19] x86/relocate_kernel: Use named labels for less confusion

[H. Peter Anvin]

On 5/29/24 03:47, Nikolay Borisov wrote:
>>
>> diff --git a/arch/x86/kernel/relocate_kernel_64.S 
>> b/arch/x86/kernel/relocate_kernel_64.S
>> index 56cab1bb25f5..085eef5c3904 100644
>> --- a/arch/x86/kernel/relocate_kernel_64.S
>> +++ b/arch/x86/kernel/relocate_kernel_64.S
>> @@ -148,9 +148,10 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
>>        */
>>       movl    $X86_CR4_PAE, %eax
>>       testq    $X86_CR4_LA57, %r13
>> -    jz    1f
>> +    jz    .Lno_la57
>>       orl    $X86_CR4_LA57, %eax
>> -1:
>> +.Lno_la57:
>> +
>>       movq    %rax, %cr4
>>       jmp 1f
> 
> That jmp 1f becomes redundant now as it simply jumps 1 line below.
> 

Uh... am I the only person to notice that ALL that is needed here is:

	andl $(X86_CR4_PAE|X86_CR4_LA57), %r13d
	movq %r13, %rax

... since %r13 is dead afterwards, and PAE *will* have been set in %r13 
already?

I don't believe that this specific jmp is actually needed -- there are 
several more synchronizing jumps later -- but it doesn't hurt.

However, if the effort is for improving the readability, it might be 
worthwhile to encapsulate the "jmp 1f; 1:" as a macro, e.g. "SYNC_CODE".

	-hpa