On Tue, Jul 24, 2012 at 11:55:30AM +0100, Cyril Chemparathy wrote:
> On 7/24/2012 6:37 AM, Catalin Marinas wrote:
> > On Tue, Jul 24, 2012 at 02:09:05AM +0100, Cyril Chemparathy wrote:
> >> This patch fixes up the types used when converting back and forth between
> >> physical and virtual addresses.
> >>
> >> Signed-off-by: Vitaly Andrianov <vita...@ti.com>
> >> Signed-off-by: Cyril Chemparathy <cy...@ti.com>
> >> ---
> >> arch/arm/include/asm/memory.h | 17 +++++++++++------
> >> 1 file changed, 11 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
> >> index fcb5757..7629dfe 100644
> >> --- a/arch/arm/include/asm/memory.h
> >> +++ b/arch/arm/include/asm/memory.h
> >> @@ -169,22 +169,27 @@ extern unsigned long __pv_phys_offset;
> >> : "=r" (to) \
> >> : "r" (from), "I" (type))
> >>
> >> -static inline unsigned long __virt_to_phys(unsigned long x)
> >> +static inline phys_addr_t __virt_to_phys(unsigned long x)
> >> {
> >> unsigned long t;
> >> __pv_stub(x, t, "add", __PV_BITS_31_24);
> >> return t;
> >> }
> >>
> >> -static inline unsigned long __phys_to_virt(unsigned long x)
> >> +static inline unsigned long __phys_to_virt(phys_addr_t x)
> >> {
> >> unsigned long t;
> >> __pv_stub(x, t, "sub", __PV_BITS_31_24);
> >> return t;
> >> }
> >
> > BTW, I would prefer if the phys-to-virt patching was fixed as well. It
> > shouldn't be difficult.
>
> On that topic - yes, we have this on our radar, but in our case we;re
> talking about patching (in head.S) and then repatching (at switch over).
>
> One of the ideas we've been bouncing around has been to convert the
> phys-virt patch code into arithmetic on PFNs. This way we don't have to
> get too messy with 64-bit in the patch code, and we can use the same
> patch code for both phys_to_virt and virt_to_phys. Thoughts on this
> approach?
It may be slightly less efficient with Thumb-2 code as we can't have add
and lsl in the same instruction. It may anyway be faster than reading a
global variable.
But I suspect you can just mask out the top 32-bit part of a physical
address when converting to virtual. The opposite may also work, you just
have some constant in the top 32-bit part of the phys address. Note that
virt_to_phys is only valid for the lowmem, so 32-bit arithmetic with
some constant for the top 32-bit should be enough.
--
Catalin
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