Christophe,
On Wed, Dec 07 2022 at 16:53, Christophe Leroy wrote:
> Le 07/12/2022 à 16:36, Thomas Gleixner a écrit :
>> The "use free space in existing mappings" mechanism is not required to
>> be PMD_SIZE based, right?
Correct. I just used it for the example.
>> Large page size, strict separation:
>>
>> struct mod_alloc_type_params {
>> [MOD_ALLOC_TYPE_TEXT] = {
>> .mapto_type = MOD_ALLOC_TYPE_TEXT,
>> .flags = FLAG_SHARED_PMD | FLAG_SECOND_ADDRESS_SPACE,
>> .granularity = PMD_SIZE,
>> .alignment = MOD_ARCH_ALIGNMENT,
>> .start[0] = MODULES_VADDR,
>> .end[0] = MODULES_END,
>> .start[1] = MODULES_VADDR_2ND,
>> .end[1] = MODULES_END_2ND,
>> .pgprot = PAGE_KERNEL_EXEC,
>> .fill = text_poke,
>> .invalidate = text_poke_invalidate,
>> },
>
> Don't restrict implementation to PMD_SIZE only.
>
> On powerpc 8xx:
> - PMD_SIZE is 4 Mbytes
> - Large pages are 512 kbytes and 8 Mbytes.
>
> It even has large pages of size 16 kbytes when build for 4k normal page
> size.
@granularity takes any size which is valid from the architecture side
and can handle the @pgprot distinctions.
That's why I separated functionality and configuration.
Note, it's not strict compile time configuration. You can either build
it completely dynamic at boot or have a static configuration structure
as compile time default.
That static default might be __initconst for architectures where there
is no boot time detection and change required, but can be __initdata for
those which need to adjust it to the needs of the detected CPU/platform
before feeding it into the module allocator init function.
Does that answer your question?
Thanks,
tglx
