Re: [PATCH 5/8] x86/IDT: Make idt_tables[] be per_cpu(idt)

[Jan Beulich <jbeulich@xxxxxxxx>]

On 25.02.2025 16:40, Andrew Cooper wrote:
> On 25/02/2025 9:07 am, Jan Beulich wrote:
>> On 24.02.2025 17:05, Andrew Cooper wrote:
>>> --- a/xen/arch/x86/cpu/common.c
>>> +++ b/xen/arch/x86/cpu/common.c
>>> @@ -819,6 +819,7 @@ void load_system_tables(void)
>>>      * support using ARRAY_SIZE against per-cpu variables.
>>>      */
>>>     struct tss_page *tss_page = &this_cpu(tss_page);
>>> +        idt_entry_t *idt = this_cpu(idt);
>> Nit: Tab indentation here.
> 
> Yeah, I noticed that only after sending the email.  Other parts of the
> FRED series vastly changes this function.
> 
>>
>>> @@ -830,7 +831,7 @@ void load_system_tables(void)
>>>             .limit = LAST_RESERVED_GDT_BYTE,
>>>     };
>>>     const struct desc_ptr idtr = {
>>> -           .base = (unsigned long)idt_tables[cpu],
>>> +           .base = (unsigned long)idt,
>>>             .limit = sizeof(bsp_idt) - 1,
>>>     };
>> Coming back to the comment on the earlier patch: Now that you touch all
>> of the idt_tables[] uses anyway, ...
>>
>>> @@ -30,7 +31,7 @@ typedef union {
>>>  } idt_entry_t;
>>>  
>>>  extern idt_entry_t bsp_idt[X86_IDT_VECTORS];
>>> -extern idt_entry_t *idt_tables[];
>>> +DECLARE_PER_CPU(idt_entry_t *, idt);
>> ... this probably really ought to become
>>
>> DECLARE_PER_CPU(idt_entry_t (*)[X86_IDT_VECTORS], idt);
>>
>> ?
> 
> I'm afraid this doesn't compile.
> 
> arch/x86/crash.c:66:17: error: passing argument 1 of ‘set_ist’ from
> incompatible pointer type [-Werror=incompatible-pointer-types]
> ...
> note: expected ‘volatile idt_entry_t *’ but argument is of type
> ‘idt_entry_t (*)[256]’
> 
> Similarly {en,dis}able_each_ist() and _set_gate_lower().

Well, did you adjust the use sites? As said in the respective comment on
patch 4, that'll be necessary (to account for the abstract extra level of
indirection; generated code ought to not change).

Jan