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Date:   Fri, 27 Apr 2018 08:28:27 +0200
From:   Ingo Molnar <mingo@kernel.org>
To:     "Kani, Toshi" <toshi.kani@hpe.com>
Cc:     "tglx@linutronix.de" <tglx@linutronix.de>,
        "joro@8bytes.org" <joro@8bytes.org>,
        "mingo@redhat.com" <mingo@redhat.com>,
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        "bp@suse.de" <bp@suse.de>,
        "willy@infradead.org" <willy@infradead.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>,
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        "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        "hpa@zytor.com" <hpa@zytor.com>, "Hocko, Michal" <MHocko@suse.com>,
        "jroedel@suse.de" <jroedel@suse.de>
Subject: Re: [PATCH] Revert "x86/mm: implement free pmd/pte page interfaces"
Message-ID: <20180427062827.js6kwkwye4ewkuz4@gmail.com>
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* Kani, Toshi <toshi.kani@hpe.com> wrote:

> On Thu, 2018-04-26 at 17:14 +0200, Joerg Roedel wrote:
> > From: Joerg Roedel <jroedel@suse.de>
> > 
> > This reverts commit 28ee90fe6048fa7b7ceaeb8831c0e4e454a4cf89.
> > 
> > This commit is broken for x86, as it unmaps the PTE and PMD
> > pages and immediatly frees them without doing a TLB flush.
> > 
> > Further this lacks synchronization with other page-tables in
> > the system when the PMD pages are not shared between
> > mm_structs.
> > 
> > On x86-32 with PAE and PTI patches on-top this patch
> > triggers the BUG_ON in vmalloc_sync_one() because the kernel
> > and the process page-table were not synchronized.
> > 
> > Signed-off-by: Joerg Roedel <jroedel@suse.de>
> 
> I do not agree with the comments and this revert.  Let's discuss further
> on the original thread.

The original patch is totally broken (it's based on a misunderstanding), so unless 
you have a fix the revert is justified.

Thanks,

	Ingo