linux-kernel - Re: [PATCH 3/3] x86/mm: disable ioremap free page handling on x86-PAE

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Date:   Wed, 9 May 2018 15:47:19 +0000
From:   "Kani, Toshi" <toshi.kani@....com>
To:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "hpa@...or.com" <hpa@...or.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "Hocko, Michal" <MHocko@...e.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "mingo@...hat.com" <mingo@...hat.com>
CC:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "cpandya@...eaurora.org" <cpandya@...eaurora.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH 3/3] x86/mm: disable ioremap free page handling on x86-PAE

On Mon, 2018-04-30 at 11:59 -0600, Toshi Kani wrote:
> ioremap() supports pmd mappings on x86-PAE.  However, kernel's pmd
> tables are not shared among processes on x86-PAE.  Therefore, any
> update to sync'd pmd entries need re-syncing.  Freeing a pte page
> also leads to a vmalloc fault and hits the BUG_ON in vmalloc_sync_one().
> 
> Disable free page handling on x86-PAE.  pud_free_pmd_page() and
> pmd_free_pte_page() simply return 0 if a given pud/pmd entry is present.
> This assures that ioremap() does not update sync'd pmd entries at the
> cost of falling back to pte mappings.
> 
> Fixes: 28ee90fe6048 ("x86/mm: implement free pmd/pte page interfaces")
> Reported-by: Joerg Roedel <joro@...tes.org>

Hi Joerg,

Does it solve your problem?  Let me know if you have any issue with the
series. 

Thanks,
-Toshi