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SubjectRe: [PATCH 2 of 7] x86/pvops: add a paravirt_ident functions to allow special patching
Rusty Russell wrote:
> On Thursday 29 January 2009 09:05:02 Jeremy Fitzhardinge wrote:
>
>> void _paravirt_nop(void);
>> +u32 _paravirt_ident_32(u32);
>> +u64 _paravirt_ident_64(u64);
>> +
>> #define paravirt_nop ((void *)_paravirt_nop)
>>
>
> So, we used a void * cast for the paravirt_nop case, but you decided to use explicit types for the ident cases?
>

Yes. Partly because any nop function is going to be basically
equivalent to (void (*)(void)), but the concrete types for the ident
function will vary (pointer, scalar, structure, etc).

>> if (opfunc == NULL)
>> /* If there's no function, patch it with a ud2a (BUG) */
>> ret = paravirt_patch_insns(insnbuf, len, ud2a, ud2a+sizeof(ud2a));
>> - else if (opfunc == paravirt_nop)
>> + else if (opfunc == _paravirt_nop)
>> /* If the operation is a nop, then nop the callsite */
>> ret = paravirt_patch_nop();
>>
>
> Gratuitous change?
>

To make it consistent with the newly added lines following. And its
slightly more correct.

>
>> +typedef pte_t make_pte_t(pteval_t);
>> +typedef pmd_t make_pmd_t(pmdval_t);
>> +typedef pud_t make_pud_t(pudval_t);
>> +typedef pgd_t make_pgd_t(pgdval_t);
>> +
>> +typedef pteval_t pte_val_t(pte_t);
>> +typedef pmdval_t pmd_val_t(pmd_t);
>> +typedef pudval_t pud_val_t(pud_t);
>> +typedef pgdval_t pgd_val_t(pgd_t);
>> +
>> +
>> +#if defined(CONFIG_X86_32) && !defined(CONFIG_X86_PAE)
>> +/* 32-bit pagetable entries */
>> +#define paravirt_native_make_pte (make_pte_t *)_paravirt_ident_32
>> +#define paravirt_native_pte_val (pte_val_t *)_paravirt_ident_32
>> +
>> +#define paravirt_native_make_pmd (make_pmd_t *)_paravirt_ident_32
>> +#define paravirt_native_pmd_val (pmd_val_t *)_paravirt_ident_32
>> +
>> +#define paravirt_native_make_pud (make_pud_t *)_paravirt_ident_32
>> +#define paravirt_native_pud_val (pud_val_t *)_paravirt_ident_32
>> +
>> +#define paravirt_native_make_pgd (make_pgd_t *)_paravirt_ident_32
>> +#define paravirt_native_pgd_val (pgd_val_t *)_paravirt_ident_32
>> +#else
>> +/* 64-bit pagetable entries */
>> +#define paravirt_native_make_pte (make_pte_t *)_paravirt_ident_64
>> +#define paravirt_native_pte_val (pte_val_t *)_paravirt_ident_64
>> +
>> +#define paravirt_native_make_pmd (make_pmd_t *)_paravirt_ident_64
>> +#define paravirt_native_pmd_val (pmd_val_t *)_paravirt_ident_64
>> +
>> +#define paravirt_native_make_pud (make_pud_t *)_paravirt_ident_64
>> +#define paravirt_native_pud_val (pud_val_t *)_paravirt_ident_64
>> +
>> +#define paravirt_native_make_pgd (make_pgd_t *)_paravirt_ident_64
>> +#define paravirt_native_pgd_val (pgd_val_t *)_paravirt_ident_64
>> +#endif
>>
>
> I think I prefer:
>
> /* make_pte etc and pgd_val etc are identity functions. */
> #define paravirt_native_page_op \
> (sizeof(pte_t) == sizeof(u64) ? paravirt_ident_64 : paravirt_ident_32)
>
> Then use that everywhere rather than these defines?
>

They disappear later in the series anyway.

> But it's a minor point; the code seems perfectly sound.
>

Great, thanks for reviewing.

J


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