linux-kernel - Re: [PATCH v2] x86/gart/kcore: Exclude GART aperture from kcore

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Date:   Tue, 19 Feb 2019 16:00:54 +0800
From:   Kairui Song <kasong@...hat.com>
To:     Baoquan He <bhe@...hat.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, jbohac@...e.cz,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>, osandov@...com,
        Bhupesh Sharma <bhsharma@...hat.com>,
        Dave Young <dyoung@...hat.com>
Subject: Re: [PATCH v2] x86/gart/kcore: Exclude GART aperture from kcore

On Thu, Jan 24, 2019 at 10:17 AM Baoquan He <bhe@...hat.com> wrote:
>
> On 01/23/19 at 10:50pm, Kairui Song wrote:
> > > >  int fix_aperture __initdata = 1;
> > > >
> > > > -#ifdef CONFIG_PROC_VMCORE
> > > > +#if defined(CONFIG_PROC_VMCORE) || defined(CONFIG_PROC_KCORE)
> > > >  /*
> > > >   * If the first kernel maps the aperture over e820 RAM, the kdump kernel will
> > > >   * use the same range because it will remain configured in the northbridge.
> > > > @@ -66,7 +67,7 @@ int fix_aperture __initdata = 1;
> > > >   */
> > > >  static unsigned long aperture_pfn_start, aperture_page_count;
> > > >
> > > > -static int gart_oldmem_pfn_is_ram(unsigned long pfn)
> > > > +static int gart_mem_pfn_is_ram(unsigned long pfn)
> > > >  {
> > > >       return likely((pfn < aperture_pfn_start) ||
> > > >                     (pfn >= aperture_pfn_start + aperture_page_count));
> > > > @@ -76,7 +77,12 @@ static void exclude_from_vmcore(u64 aper_base, u32 aper_order)
> > >
> > > Shouldn't this function name be changed? It's not only handling vmcore
> > > stuff any more, but also kcore. And this function is not excluding, but
> > > resgistering.
> > >
> > > Other than this, it looks good to me.
> > >
> > > Thanks
> > > Baoquan
> > >
> >
> > Good suggestion, it's good to change this function name too to avoid
> > any misleading. This patch hasn't got any other reviews recently, I'll
> > update it shortly.
>
> There's more.
>
> These two are doing the same thing:
>   register_mem_pfn_is_ram
>   register_oldmem_pfn_is_ram
>
> Need remove one of them and put it in a right place. Furthermore, may
> need see if there's existing function which is used to register a
> function to a hook.
>
> Secondly, exclude_from_vmcore() is not excluding anthing, it's only
> registering a function which is used to judge if oldmem/pfn is ram. Need
> rename it.
>
> Thanks
> Baoquan

Thanks a lot for the review! I've sent V3, using a different approach.
It's true repeating the hook infrastructure cause duplication, but I
see vmcore/kcore didn't share much code, so instead of sharing a
common hook infrastructure / registering entry, I used a new kcore
memory mapping list enum type to fix it, it also introduced less code.
Please have a look at V3, let me know how you think about it, thanks!


--
Best Regards,
Kairui Song