linux-kernel - RE: [PATCH v2] arm64: Fix double TCR_T0SZ

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Date: Mon, 8 Apr 2024 11:19:25 +0900
From: "Seongsu Park" <sgsu.park@...sung.com>
To: "'Mark Rutland'" <mark.rutland@....com>
Cc: <will@...nel.org>, <catalin.marinas@....com>, <ardb@...nel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
	"'Leem	ChaeHoon'" <infinite.run@...il.com>, "'Gyeonggeon Choi'"
	<gychoi@...dent.42seoul.kr>, "'Soomin Cho'" <to.soomin@...il.com>, "'DaeRo
 Lee'" <skseofh@...il.com>, "'kmasta'" <kmasta.study@...il.com>
Subject: RE: [PATCH v2] arm64: Fix double TCR_T0SZ_OFFSET shift



> On Wed, Apr 03, 2024 at 11:42:36AM +0900, Seongsu Park wrote:
> > We have already shifted the value of t0sz in TCR_T0SZ by
TCR_T0SZ_OFFSET.
> > So, the TCR_T0SZ_OFFSET shift here should be removed.
> 
> Can we please write a better commit message?
> 
> This doesn't explain:
> 
> * Where we have already shifted the value of t0sz, nor why it makes sense
> to do
>   that there.
> 
> * That the value of TCR_T0SZ_OFFSET is 0, and hence shifting this
> repeatedly is
>   beningn, and this patch is a cleanup rather than a fix.
> 
> Mark.
Thank you for feedback. I'll send v3 patch.
In v3, We will upgrade the commit message, and add the cpu_set_tcr_t0sz
macro.
Please check v3!
> 
> > Co-developed-by: Leem ChaeHoon <infinite.run@...il.com>
> > Signed-off-by: Leem ChaeHoon <infinite.run@...il.com>
> > Co-developed-by: Gyeonggeon Choi <gychoi@...dent.42seoul.kr>
> > Signed-off-by: Gyeonggeon Choi <gychoi@...dent.42seoul.kr>
> > Co-developed-by: Soomin Cho <to.soomin@...il.com>
> > Signed-off-by: Soomin Cho <to.soomin@...il.com>
> > Co-developed-by: DaeRo Lee <skseofh@...il.com>
> > Signed-off-by: DaeRo Lee <skseofh@...il.com>
> > Co-developed-by: kmasta <kmasta.study@...il.com>
> > Signed-off-by: kmasta <kmasta.study@...il.com>
> > Signed-off-by: Seongsu Park <sgsu.park@...sung.com>
> > ---
> >
> > Changes in v2:
> > - Condition is updated
> >
> > ---
> >  arch/arm64/include/asm/mmu_context.h | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/mmu_context.h
> > b/arch/arm64/include/asm/mmu_context.h
> > index c768d16b81a4..bd19f4c758b7 100644
> > --- a/arch/arm64/include/asm/mmu_context.h
> > +++ b/arch/arm64/include/asm/mmu_context.h
> > @@ -72,11 +72,11 @@ static inline void __cpu_set_tcr_t0sz(unsigned
> > long t0sz)  {
> >  	unsigned long tcr = read_sysreg(tcr_el1);
> >
> > -	if ((tcr & TCR_T0SZ_MASK) >> TCR_T0SZ_OFFSET == t0sz)
> > +	if ((tcr & TCR_T0SZ_MASK) == t0sz)
> >  		return;
> >
> >  	tcr &= ~TCR_T0SZ_MASK;
> > -	tcr |= t0sz << TCR_T0SZ_OFFSET;
> > +	tcr |= t0sz;
> >  	write_sysreg(tcr, tcr_el1);
> >  	isb();
> >  }
> > --
> > 2.34.1
> >