Messages in this thread | | | Date | Thu, 13 Nov 2014 10:15:26 +0100 | From | Juergen Gross <> | Subject | Re: [PATCH V3 6/8] xen: Hide get_phys_to_machine() to be able to tune common path |
| |
On 11/12/2014 11:18 PM, Konrad Rzeszutek Wilk wrote: > On Tue, Nov 11, 2014 at 06:43:44AM +0100, Juergen Gross wrote: >> Today get_phys_to_machine() is always called when the mfn for a pfn >> is to be obtained. Add a wrapper __pfn_to_mfn() as inline function >> to be able to avoid calling get_phys_to_machine() when possible as > > s/when/where/
No. It's not a matter of the caller, but of the p2m list entry.
>> soon as the switch to a linear mapped p2m list has been done. > > But your inline function still calls get_phys_to_machine?
Sure. The switch is done in the next patch. David asked me to split the patch doing the preparation by adding __pfn_tom_mfn() in an own patch.
> > >> >> Signed-off-by: Juergen Gross <jgross@suse.com> >> --- >> arch/x86/include/asm/xen/page.h | 27 +++++++++++++++++++++------ >> arch/x86/xen/mmu.c | 2 +- >> arch/x86/xen/p2m.c | 6 +++--- >> 3 files changed, 25 insertions(+), 10 deletions(-) >> >> diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h >> index 28fa795..07d8a7b 100644 >> --- a/arch/x86/include/asm/xen/page.h >> +++ b/arch/x86/include/asm/xen/page.h >> @@ -59,6 +59,22 @@ extern int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops, >> struct page **pages, unsigned int count); >> extern unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn); >> >> +/* >> + * When to use pfn_to_mfn(), __pfn_to_mfn() or get_phys_to_machine(): >> + * - pfn_to_mfn() returns either INVALID_P2M_ENTRY or the mfn. In case of an >> + * identity entry the identity indicator will be cleared. > > Why don't you say : In case of identity PFN the same PFN is returned. > > But you did miss that also the FOREIGN_FRAME_BIT is cleared.
I'll reword the comment.
> >> + * - __pfn_to_mfn() returns the found entry of the p2m table. A possibly set > > s/of the/in the/ >> + * identity indicator will be still set. __pfn_to_mfn() is encapsulating > .. be still set if the PFN is an identity one. >> + * get_phys_to_machine() and might skip that function if possible to speed >> + * up the common path. > > How is is skipping that function? The patch below does no such thing?
The next patch in this series does.
> >> + * - get_phys_to_machine() is basically the same as __pfn_to_mfn(), but >> + * without any short cuts for the common fast path. > > Right. Perhpas we should call it 'slow_p2m' instead of the 'get_phys_to_machine'.
That's a matter of taste, I think. I can change it if nobody else objects.
Juergen
| |