Re: [PATCH 2/3] x86/alternatives: Rework get_ideal_nops()

On 05.08.2026 08:34, Andrew Cooper wrote:
> On 05/08/2026 7:04 am, Jan Beulich wrote:
>> On 04.08.2026 19:13, Andrew Cooper wrote:
>>> On 02/06/2025 10:57 am, Jan Beulich wrote:
>>>> On 22.05.2025 17:00, Andrew Cooper wrote:
>>>>> --- a/xen/arch/x86/alternative.c
>>>>> +++ b/xen/arch/x86/alternative.c
>>>>> @@ -20,7 +20,7 @@
>>>>>  #define MAX_PATCH_LEN (255-1)
>>>>>  
>>>>>  #ifdef K8_NOP1
>>>>> -static const unsigned char k8nops[] init_or_livepatch_const = {
>>>>> +static const unsigned char k8_nops[] init_or_livepatch_const = {
>>>>>      K8_NOP1,
>>>>>      K8_NOP2,
>>>>>      K8_NOP3,
>>>>> @@ -31,22 +31,10 @@ static const unsigned char k8nops[] init_or_livepatch_const = {
>>>>>      K8_NOP8,
>>>>>      K8_NOP9,
>>>>>  };
>>>>> -static const unsigned char * const k8_nops[ASM_NOP_MAX+1] init_or_livepatch_constrel = {
>>>> ... the (at least visual) connection to ASM_NOP_MAX. Could I talk you into
>>>> adding build time array-size checks for both arrays, to restore the
>>>> connection?
>>> Sorry, but I have no idea what you're asking for here.
>>     BUILD_BUG_ON(ARRAY_SIZE(k8_nops) != ASM_NOP_MAX);
>>     BUILD_BUG_ON(ARRAY_SIZE(p6_nops) != ASM_NOP_MAX);
> 
> The arrays are 45 bytes (and elements) long.  ASM_NOP_MAX is 9.

Oh, right, sorry:

     BUILD_BUG_ON(ARRAY_SIZE(k8_nops) != (ASM_NOP_MAX * (ASM_NOP_MAX + 1)) / 2);
     BUILD_BUG_ON(ARRAY_SIZE(p6_nops) != (ASM_NOP_MAX * (ASM_NOP_MAX + 1)) / 2);

Jan