Re: [Xen-devel] [PATCH] xen: arm: remove unnecessary cache flush in write_pte

[Tim Deegan <tim@xxxxxxx>]

At 15:57 +0100 on 29 Jul (1375113450), Ian Campbell wrote:
> ping?
> 
> On Wed, 2013-07-17 at 12:19 +0100, Ian Campbell wrote:
> > On a ARMv7/v8 SMP system the MMU is coherent
> > 
> > Suggested-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> > Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> > ---
> >  xen/include/asm-arm/arm32/page.h |    2 --
> >  xen/include/asm-arm/arm64/page.h |    2 --
> >  2 files changed, 0 insertions(+), 4 deletions(-)
> > 
> > diff --git a/xen/include/asm-arm/arm32/page.h 
> > b/xen/include/asm-arm/arm32/page.h
> > index 38bcffd..3a06a22 100644
> > --- a/xen/include/asm-arm/arm32/page.h
> > +++ b/xen/include/asm-arm/arm32/page.h
> > @@ -16,8 +16,6 @@ static inline void write_pte(lpae_t *p, lpae_t pte)
> >          /* Safely write the entry (STRD is atomic on CPUs that support 
> > LPAE) */
> >          "strd %0, %H0, [%1];"
> >          "dsb;"
> > -        /* Push this cacheline to the PoC so the rest of the system sees 
> > it. */
> > -        STORE_CP32(1, DCCMVAC)
> >          /* Ensure that the data flush is completed before proceeding */
> >          "dsb;"

We should drop this DSB and its comment too (likewise for the second
'dsb sy' below).  With that change, Acked-by: Tim Deegan <tim@xxxxxxx>.

Tim.

> >          : : "r" (pte.bits), "r" (p) : "memory");
> > diff --git a/xen/include/asm-arm/arm64/page.h 
> > b/xen/include/asm-arm/arm64/page.h
> > index bd48fe3..542f886 100644
> > --- a/xen/include/asm-arm/arm64/page.h
> > +++ b/xen/include/asm-arm/arm64/page.h
> > @@ -11,8 +11,6 @@ static inline void write_pte(lpae_t *p, lpae_t pte)
> >          "dsb sy;"
> >          "str %0, [%1];"         /* Write the entry */
> >          "dsb sy;"
> > -        /* Push this cacheline to the PoC so the rest of the system sees 
> > it. */
> > -        "dc cvac, %1;"
> >          /* Ensure that the data flush is completed before proceeding */
> >          "dsb sy;"
> >          : : "r" (pte.bits), "r" (p) : "memory");
> 
> 

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