Hi, On Fri, Sep 23, 2022 at 1:53 AM Kirill A . Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> wrote: > > 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? I think that would be useful. In pKVM we don't need to know the order, and I had to use a dummy variable when porting V7. Cheers, /fuad > -- > Kiryl Shutsemau / Kirill A. Shutemov
