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Re: [MIPS] SB1: Build fix: delete initialization of flush_icache_page po

To: manoje@broadcom.com
Subject: Re: [MIPS] SB1: Build fix: delete initialization of flush_icache_page pointer.
From: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Date: Thu, 28 Sep 2006 13:27:12 +0900 (JST)
Cc: linux-mips@linux-mips.org, ralf@linux-mips.org, mark.e.mason@broadcom.com
In-reply-to: <710F16C36810444CA2F5821E5EAB7F230A0E91@NT-SJCA-0752.brcm.ad.broadcom.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20060927.235804.95064004.anemo@mba.ocn.ne.jp> <710F16C36810444CA2F5821E5EAB7F230A0E91@NT-SJCA-0752.brcm.ad.broadcom.com>
Sender: linux-mips-bounce@linux-mips.org
On Wed, 27 Sep 2006 19:17:16 -0700, "Manoj Ekbote" <manoje@broadcom.com> wrote:
> I added a line that initializes the flush_icache_page pointer in
> sb1_cache_init.
> The below method worked. The SMP kernel boots fine now. Removing parts
> of local_sb1_flush_icache_page doesn't help. It looks like
> flush_icache_page in mm/memory.c:do_no_page is needed. Removing it will
> fail the boot process.

Thank you for testing.

Now I'm wondering why do_no_page() works on SMP.

        if (pte_none(*page_table)) {
                flush_icache_page(vma, new_page);
                entry = mk_pte(new_page, vma->vm_page_prot);
                if (write_access)
                        entry = maybe_mkwrite(pte_mkdirty(entry), vma);
                set_pte_at(mm, address, page_table, entry);
...
        } else {
                /* One of our sibling threads was faster, back out. */
                page_cache_release(new_page);
                goto unlock;
        }

        /* no need to invalidate: a not-present page shouldn't be cached */
        update_mmu_cache(vma, address, entry);

Other CPU might be able to load new pte value just after set_ste_at(),
but dcache is not flushed until update_mmu_cache().  Maybe I missed
something...

> I am wondering if people have booted the latest tree on non-Broadcom
> boards...curious to know if the removal of flush_icache_page has
> affected them.

Yes, Ralf and Thiemo said even some SB1 boards can work fine without
flush_icache_page.

---
Atsushi Nemoto

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