linux-kernel - Re: [PATCH v2 5/5] x86/mm: Drop usage of __flush_tlb_all() in kernel_physical_mapping

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Date:   Mon, 3 Dec 2018 09:18:54 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Dan Williams <dan.j.williams@...el.com>, sashal@...nel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        stable <stable@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        X86 ML <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 5/5] x86/mm: Drop usage of __flush_tlb_all() in
 kernel_physical_mapping_init()

On 12/2/18 9:04 AM, Dan Williams wrote:
>> This patch on it's own doesn't apply to any of the stable trees, does it
>> maybe depend on some of the previous patches in this series?
> It does not strictly depend on them, but it does need to be rebased
> without them. The minimum patch for -stable are these
> __flush_tlb_all() removals, but without the
> set_{pte,pmd,pud,p4d,pgd}_safe() conversion. It's also an option to
> backport those helpers, and conversion but I'd defer to x86/mm folks
> to make that call.

I think we should skip backporting the helpers for now.  Hopefully,
mainline will help us catch bugs with those helpers and we can get the
fixes for those bugs backported if they show up.

I mostly say this because with the addition of the 5-level paging code,
there's been a lot of churn in the area of these helpers.  They will be
a mild pain to backport, and I'd expect more bugs from the backports
than from the lack of the new helpers.