Re: [PATCH v6 03/11] mm, x86: Add support for eXclusive Page Frame Ownership (XPFO)

Tycho Andersen
2017-09-08T14:58:15Z

On Fri, Sep 08, 2017 at 12:51:40AM -0700, Christoph Hellwig wrote:
> > +#include <linux/xpfo.h>
> >
> > #include <asm/cacheflush.h>
> >
> > @@ -55,24 +56,34 @@ static inline struct page *kmap_to_page(void *addr)
> > #ifndef ARCH_HAS_KMAP
> > static inline void *kmap(struct page *page)
> > {
> > + void *kaddr;
> > +
> > might_sleep();
> > - return page_address(page);
> > + kaddr = page_address(page);
> > + xpfo_kmap(kaddr, page);
> > + return kaddr;
> > }
> >
> > static inline void kunmap(struct page *page)
> > {
> > + xpfo_kunmap(page_address(page), page);
> > }
> >
> > static inline void *kmap_atomic(struct page *page)
> > {
> > + void *kaddr;
> > +
> > preempt_disable();
> > pagefault_disable();
> > - return page_address(page);
> > + kaddr = page_address(page);
> > + xpfo_kmap(kaddr, page);
> > + return kaddr;
> > }
>
> It seems to me like we should simply direct to pure xpfo
> implementations for the !HIGHMEM && XPFO case. - that is
> just have the prototypes for kmap, kunmap and co in
> linux/highmem.h and implement them in xpfo under those names.
>
> Instead of sprinkling them around.

Ok, IIUC we'll still need a #ifdef CONFIG_XPFO in this file, but at
least the implementations here won't have a diff. I'll make this
change, and all the others you've suggested.

Thanks!

Tycho