On Thu, Sep 22, 2022 at 07:49:18PM +0000, Sean Christopherson wrote: > On Thu, Sep 22, 2022, Wang, Wei W wrote: > > On Thursday, September 15, 2022 10:29 PM, Chao Peng wrote: > > > +int inaccessible_get_pfn(struct file *file, pgoff_t offset, pfn_t *pfn, > > > + int *order) > > > > Better to remove "order" from this interface? > > Hard 'no'. > > > Some callers only need to get pfn, and no need to bother with > > defining and inputting something unused. For callers who need the "order", > > can easily get it via thp_order(pfn_to_page(pfn)) on their own. > > That requires (a) assuming the pfn is backed by struct page, and (b) assuming the > struct page is a transparent huge page. That might be true for the current > implementation, but it most certainly will not always be true. > > KVM originally did things like this, where there was dedicated code for THP vs. > HugeTLB, and it was a mess. The goal here is very much to avoid repeating those > mistakes. Have the backing store _tell_ KVM how big the mapping is, don't force > KVM to rediscover the info on its own. I guess we can allow order pointer to be NULL to cover caller that don't need to know the order. Is it useful? -- Kiryl Shutsemau / Kirill A. Shutemov
