Re: [PATCH Part2 v6 09/49] x86/fault: Add support to handle the RMP fault for user address

[Jarkko Sakkinen]

On Tue, Sep 06, 2022 at 01:25:10PM +0300, Jarkko Sakkinen wrote:
> On Tue, Aug 09, 2022 at 06:55:43PM +0200, Borislav Petkov wrote:
> > On Mon, Jun 20, 2022 at 11:03:43PM +0000, Ashish Kalra wrote:
> > > +	pfn = pte_pfn(*pte);
> > > +
> > > +	/* If its large page then calculte the fault pfn */
> > > +	if (level > PG_LEVEL_4K) {
> > > +		unsigned long mask;
> > > +
> > > +		mask = pages_per_hpage(level) - pages_per_hpage(level - 1);
> > > +		pfn |= (address >> PAGE_SHIFT) & mask;
> > 
> > Oh boy, this is unnecessarily complicated. Isn't this
> > 
> > 	pfn |= pud_index(address);
> > 
> > or
> > 	pfn |= pmd_index(address);
> 
> I played with this a bit and ended up with
> 
>         pfn = pte_pfn(*pte) | PFN_DOWN(address & page_level_mask(level - 1));
> 
> Unless I got something terribly wrong, this should do the
> same (see the attached patch) as the existing calculations.

IMHO a better name for this function would be do_user_rmp_addr_fault() as
it is more consistent with the existing function names.

BR, Jarkko