linux-kernel - Re: [PATCH] Revert "x86/mm: implement free pmd/pte page interfaces"

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Date:   Thu, 26 Apr 2018 16:29:45 +0000
From:   "Kani, Toshi" <toshi.kani@....com>
To:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "joro@...tes.org" <joro@...tes.org>,
        "mingo@...hat.com" <mingo@...hat.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "bp@...e.de" <bp@...e.de>,
        "willy@...radead.org" <willy@...radead.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "hpa@...or.com" <hpa@...or.com>, "Hocko, Michal" <MHocko@...e.com>,
        "jroedel@...e.de" <jroedel@...e.de>
Subject: Re: [PATCH] Revert "x86/mm: implement free pmd/pte page interfaces"

On Thu, 2018-04-26 at 17:14 +0200, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@...e.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@...e.de>

I do not agree with the comments and this revert.  Let's discuss further
on the original thread.

Thanks,
-Toshi