linux-kernel - Re: [PATCH V5 06/30] csky: Cache and TLB routines

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Message-ID: <20180927070859.GC5254@hirez.programming.kicks-ass.net>
Date:   Thu, 27 Sep 2018 09:08:59 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Guo Ren <ren_guo@...ky.com>
Cc:     akpm@...ux-foundation.org, arnd@...db.de,
        daniel.lezcano@...aro.org, davem@...emloft.net,
        gregkh@...uxfoundation.org, jason@...edaemon.net,
        marc.zyngier@....com, mark.rutland@....com,
        mchehab+samsung@...nel.org, robh@...nel.org, robh+dt@...nel.org,
        tglx@...utronix.de, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, devicetree@...r.kernel.org,
        c-sky_gcc_upstream@...ky.com, gnu-csky@...tor.com,
        green.hu@...il.com, palmer@...ive.com
Subject: Re: [PATCH V5 06/30] csky: Cache and TLB routines

On Thu, Sep 27, 2018 at 01:27:38PM +0800, Guo Ren wrote:
> On Tue, Sep 25, 2018 at 09:24:07AM +0200, Peter Zijlstra wrote:
> > On Mon, Sep 24, 2018 at 10:36:22PM +0800, Guo Ren wrote:
> > > diff --git a/arch/csky/abiv1/inc/abi/cacheflush.h b/arch/csky/abiv1/inc/abi/cacheflush.h
> > > new file mode 100644
> > > index 0000000..f0de49c
> > > --- /dev/null
> > > +++ b/arch/csky/abiv1/inc/abi/cacheflush.h

> > > +#define flush_cache_range(mm,start,end)	cache_wbinv_range(start, end)
> >                              ^^^ should be vma
> Yes, I'll change it to:
> #define flush_cache_range(mm,start,end)	cache_wbinv_all()
> 
> I'll improve it later after test.

That's not what I meant; I meant you need something like:

#define flush_cache_range(vma, start, end) cache_wbinv_range(start, end) 

The first argument is a vma, not an mm.

> > > +#endif /* __ABI_CSKY_CACHEFLUSH_H */
> > 
> > 
> > > diff --git a/arch/csky/abiv1/inc/abi/tlb.h b/arch/csky/abiv1/inc/abi/tlb.h
> > > new file mode 100644
> > > index 0000000..6d461f3
> > > --- /dev/null
> > > +++ b/arch/csky/abiv1/inc/abi/tlb.h
> > > @@ -0,0 +1,12 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
> > > +
> > > +#ifndef __ABI_CSKY_TLB_H
> > > +#define __ABI_CSKY_TLB_H
> > > +
> > > +#define tlb_start_vma(tlb, vma) \
> > > +	do { \
> > > +		if (!tlb->fullmm) \
> > > +			cache_wbinv_all(); \
> > > +	}  while (0)
> > > +#endif /* __ABI_CSKY_TLB_H */
> > 
> > That should be:
> > 
> > 	if (!tlb->fullmm)
> > 		flush_cache_range(vma, vma->vm_start, vma->vm_end);
> > 
> > Because as per the whole abiv1 vs abiv2, you don't need write back
> > invalidation for v2 at all, also, you only need to invalidate the vma
> > range, no reason to shoot everything down.
> > 
> > Also, I'll be shortly removing this:
> > 
> >   https://lkml.kernel.org/r/20180913092812.071989585@infradead.org
> Ok, I'll follow the rules.


> > > diff --git a/arch/csky/abiv2/inc/abi/cacheflush.h b/arch/csky/abiv2/inc/abi/cacheflush.h
> > > new file mode 100644
> > > index 0000000..756beb7
> > > --- /dev/null
> > > +++ b/arch/csky/abiv2/inc/abi/cacheflush.h
> > > @@ -0,0 +1,40 @@

> > > +#define flush_cache_range(vma, start, end)	do { } while (0)
> >                              ^^^ like here..
> #define flush_cache_range(vma, start, end) \
> 	do { \
> 		if (vma->vm_flags & VM_EXEC) \
> 			icache_inv_all(); \
> 	}
> 
> Hmm ?
> 

For v2, which IIUC is PIPT (as opposed to v1 which is VIPT), what you
had was correct.

I was merely pointing out that the flush_cache_range() definition was
inconsitent between v1 and v2; v1 using @mm and v2 using @vma for the
first argument.