On 05.11.20 19:45, Peter Xu wrote: > On Thu, Nov 05, 2020 at 10:59:30AM +0100, Andrew Jones wrote: >>>>> +#define PTRS_PER_PAGE(page_size) ((page_size) / 8) >>>> >>>> Doh. I think this 8 is supposed to be a 16 for s390x, considering it >>>> was dividing by 256 in its version of vm_create_default. I need >>>> guidance from s390x gurus as to whether or not I should respin though. >>>> >>>> Thanks, >>>> drew >>>> >>> >>> This is kind of tricky. The last level page table is only 2kb (256 entries = 1MB range). >>> Depending on whether the page table allocation is clever or not (you can have 2 page >>> tables in one page) this means that indeed 16 might be better. But then you actually >>> want to change the macro name to PTES_PER_PAGE? >> >> Thanks Christian, >> >> I'll respin with the macro name change and 16 for s390. > > Maybe it can also be moved to common header, but instead define PTR_SIZE for > per-arch? I'm also curious whether PTR_SIZE will equals to "sizeof(void *)", > but seems not for s390x.. Thanks, Thats why I want to change the name. It is not about the ptr size. It is about number of page table entries in a page. And as a page table is just 2kb on s390 there is a mismatch. So instead of #define PTRS_PER_PAGE(page_size) ((page_size) / 8) let us just to #define PTES_PER_PAGETABLE 256 for s390 and #define PTES_PER_PAGETABLE 512 for the others
