linux-kernel - Re: [PATCH] flush icache before set_pte take6. [4/4] optimization for cpus other than montecito

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Date:	Mon, 30 Jul 2007 22:15:50 -0600
From:	"David Mosberger-Tang" <dmosberger@...il.com>
To:	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
	"tony.luck@...el.com" <tony.luck@...el.com>,
	"Zoltan.Menyhart@...l.net" <Zoltan.Menyhart@...l.net>,
	"Christoph Lameter" <clameter@....com>
Subject: Re: [PATCH] flush icache before set_pte take6. [4/4] optimization for cpus other than montecito

This seems crazy to me.  Flushing should occur according to the
*architecture*, not model-by-model.  Even if we happen to get "lucky"
on pre-Montecito CPUs, that doesn't justify such ugly hacks.  Or you
really want to debug this *again* come next CPU?

  --david

On 7/30/07, KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
>
> Add "L2 cache is separated? check flag" as read_mostly global variable.
>
> This add one memory reference to global variable to page faults of "executable"
> map in do_wp_page(page copy case), file-mapped page fault and some system calls
> which does memory map changes. But not so bad as calling sync_icache_dcache in
> architectures which doesn't need it.
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>
>
> ---
>  arch/ia64/kernel/setup.c   |    7 +++++++
>  include/asm-ia64/pgtable.h |    3 ++-
>  2 files changed, 9 insertions(+), 1 deletion(-)
>
> Index: linux-2.6.23-rc1.test/arch/ia64/kernel/setup.c
> ===================================================================
> --- linux-2.6.23-rc1.test.orig/arch/ia64/kernel/setup.c
> +++ linux-2.6.23-rc1.test/arch/ia64/kernel/setup.c
> @@ -106,6 +106,8 @@ struct io_space io_space[MAX_IO_SPACES];
>  EXPORT_SYMBOL(io_space);
>  unsigned int num_io_spaces;
>
> +int separated_l2_icache_dcache __read_mostly;
> +
>  /*
>   * "flush_icache_range()" needs to know what processor dependent stride size to use
>   * when it makes i-cache(s) coherent with d-caches.
> @@ -718,6 +720,11 @@ get_model_name(__u8 family, __u8 model)
>                 printk(KERN_ERR
>                        "%s: Table overflow. Some processor model information will be missing\n",
>                        __FUNCTION__);
> +       /* Montecito has separated L2 Icache and Dcache. This requires
> +          synchronize Icache and Dcache before set_pte() */
> +       if (family == 0x20)
> +               separated_l2_icache_dcache = 1;
> +
>         return "Unknown";
>  }
>
> Index: linux-2.6.23-rc1.test/include/asm-ia64/pgtable.h
> ===================================================================
> --- linux-2.6.23-rc1.test.orig/include/asm-ia64/pgtable.h
> +++ linux-2.6.23-rc1.test/include/asm-ia64/pgtable.h
> @@ -489,9 +489,10 @@ extern struct page *zero_page_memmap_ptr
>   * as an executable pte.
>   */
>  extern void __sync_icache_dcache(pte_t pte);
> +extern int separated_l2_icache_dcache;
>  static inline void sync_icache_dcache(pte_t pte)
>  {
> -       if (pte_exec(pte))
> +       if (pte_exec(pte) && separated_l2_icache_dcache)
>                 __sync_icache_dcache(pte);
>  }
>  #define __HAVE_ARCH_SYNC_ICACHE_DCACHE
>
> -
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>


-- 
Mosberger Consulting LLC, http://www.mosberger-consulting.com/
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