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

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Date:   Tue, 25 Sep 2018 09:24:07 +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 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
> @@ -0,0 +1,43 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
> +
> +#ifndef __ABI_CSKY_CACHEFLUSH_H
> +#define __ABI_CSKY_CACHEFLUSH_H
> +
> +#include <linux/compiler.h>
> +#include <asm/string.h>
> +#include <asm/cache.h>
> +
> +#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
> +extern void flush_dcache_page(struct page *);
> +
> +#define flush_cache_mm(mm)		cache_wbinv_all()
> +#define flush_cache_page(vma,page,pfn)	cache_wbinv_all()
> +#define flush_cache_dup_mm(mm)		cache_wbinv_all()
> +
> +#define flush_cache_range(mm,start,end)	cache_wbinv_range(start, end)
                             ^^^ should be vma

> +#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

> 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 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#ifndef __ABI_CSKY_CACHEFLUSH_H
> +#define __ABI_CSKY_CACHEFLUSH_H
> +
> +/* Keep includes the same across arches.  */
> +#include <linux/mm.h>
> +
> +/*
> + * The cache doesn't need to be flushed when TLB entries change when
> + * the cache is mapped to physical memory, not virtual memory
> + */
> +#define flush_cache_all()			do { } while (0)
> +#define flush_cache_mm(mm)			do { } while (0)
> +#define flush_cache_dup_mm(mm)			do { } while (0)
> +#define flush_cache_range(vma, start, end)	do { } while (0)
                             ^^^ like here..

> +#endif /* __ABI_CSKY_TLB_H */