Messages in this thread | | | Date | Mon, 17 Feb 2014 11:49:34 +0000 | From | Zoltan Kiss <> | Subject | Re: [PATCH v9] xen/grant-table: Avoid m2p_override during mapping |
| |
On 16/02/14 18:36, Stefano Stabellini wrote: > On Wed, 12 Feb 2014, Zoltan Kiss wrote: >> diff --git a/arch/arm/include/asm/xen/page.h b/arch/arm/include/asm/xen/page.h >> index e0965ab..4eaeb3f 100644 >> --- a/arch/arm/include/asm/xen/page.h >> +++ b/arch/arm/include/asm/xen/page.h >> @@ -97,16 +97,15 @@ static inline pte_t *lookup_address(unsigned long address, unsigned int *level) >> return NULL; >> } >> >> -static inline int m2p_add_override(unsigned long mfn, struct page *page, >> - struct gnttab_map_grant_ref *kmap_op) >> -{ >> - return 0; >> -} >> - >> -static inline int m2p_remove_override(struct page *page, bool clear_pte) >> -{ >> - return 0; >> -} >> +extern int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops, >> + struct gnttab_map_grant_ref *kmap_ops, >> + struct page **pages, unsigned int count, >> + bool m2p_override); >> + >> +extern int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops, >> + struct gnttab_map_grant_ref *kmap_ops, >> + struct page **pages, unsigned int count, >> + bool m2p_override); > > Much much better. > The only comment I have is about this m2p_override boolean parameter. > m2p_override is now meaningless in this context, what we really want to > let the arch specific implementation know is whether the mapping is a > kernel only mapping or a userspace mapping. > Testing for kmap_ops != NULL might even be enough, but it would not > improve the interface. gntdev is the only user of this, the kmap_ops parameter there is: use_ptemod ? map->kmap_ops + offset : NULL where: use_ptemod = !xen_feature(XENFEAT_auto_translated_physmap); So I think we can't rely on kmap_ops to decide whether we should m2p_override or not.
> Is it possible to realize if the mapping is a userspace mapping by > checking for GNTMAP_application_map in map_ops? > Otherwise I would keep the boolean and rename it to user_mapping. Sounds better, but as far as I see gntdev set that flag in find_grant_ptes, which is called only
if (use_ptemod) { err = apply_to_page_range(vma->vm_mm, vma->vm_start, vma->vm_end - vma->vm_start, find_grant_ptes, map);
So if xen_feature(XENFEAT_auto_translated_physmap), we don't have kmap_ops, and GNTMAP_application_map is not set as well, but I guess we still need m2p_override. Or not? I'm a bit confused, maybe because of Monday ...
Zoli
| |