Re: [PATCH v2] powerpc: Allow flush_(inval_)dcache_range to work across ranges >4GB

[Greg Kroah-Hartman]

On Mon, Aug 26, 2019 at 10:08:26PM +0200, Christophe Leroy wrote:
> 
> 
> Le 26/08/2019 à 18:50, Greg Kroah-Hartman a écrit :
> > On Wed, Aug 21, 2019 at 10:19:27AM +1000, Alastair D'Silva wrote:
> > > From: Alastair D'Silva <alastair@xxxxxxxxxxx>
> > > 
> > > The upstream commit:
> > > 22e9c88d486a ("powerpc/64: reuse PPC32 static inline flush_dcache_range()")
> > > has a similar effect, but since it is a rewrite of the assembler to C, is
> > > too invasive for stable. This patch is a minimal fix to address the issue in
> > > assembler.
> > > 
> > > This patch applies cleanly to v5.2, v4.19 & v4.14.
> > > 
> > > When calling flush_(inval_)dcache_range with a size >4GB, we were masking
> > > off the upper 32 bits, so we would incorrectly flush a range smaller
> > > than intended.
> > > 
> > > This patch replaces the 32 bit shifts with 64 bit ones, so that
> > > the full size is accounted for.
> > > 
> > > Changelog:
> > > v2
> > >    - Add related upstream commit
> > > 
> > > Signed-off-by: Alastair D'Silva <alastair@xxxxxxxxxxx>
> > > ---
> > >   arch/powerpc/kernel/misc_64.S | 4 ++--
> > >   1 file changed, 2 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S
> > > index 1ad4089dd110..d4d096f80f4b 100644
> > > --- a/arch/powerpc/kernel/misc_64.S
> > > +++ b/arch/powerpc/kernel/misc_64.S
> > > @@ -130,7 +130,7 @@ _GLOBAL_TOC(flush_dcache_range)
> > >   	subf	r8,r6,r4		/* compute length */
> > >   	add	r8,r8,r5		/* ensure we get enough */
> > >   	lwz	r9,DCACHEL1LOGBLOCKSIZE(r10)	/* Get log-2 of dcache block size */
> > > -	srw.	r8,r8,r9		/* compute line count */
> > > +	srd.	r8,r8,r9		/* compute line count */
> > >   	beqlr				/* nothing to do? */
> > >   	mtctr	r8
> > >   0:	dcbst	0,r6
> > > @@ -148,7 +148,7 @@ _GLOBAL(flush_inval_dcache_range)
> > >   	subf	r8,r6,r4		/* compute length */
> > >   	add	r8,r8,r5		/* ensure we get enough */
> > >   	lwz	r9,DCACHEL1LOGBLOCKSIZE(r10)/* Get log-2 of dcache block size */
> > > -	srw.	r8,r8,r9		/* compute line count */
> > > +	srd.	r8,r8,r9		/* compute line count */
> > >   	beqlr				/* nothing to do? */
> > >   	sync
> > >   	isync
> > 
> > I need an ack from the powerpc maintainer(s) before I can take this.
> 
> I think you already got an ack (on v1). See
> https://patchwork.ozlabs.org/patch/1147403/#2239663

How am I supposed to remember that?  :)

greg k-h