linux-kernel - Re: [PATCHv2] x86/boot/KASLR: skip the specified crashkernel reserved region

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Date:   Fri, 29 Mar 2019 15:25:59 +0800
From:   Pingfan Liu <kernelfans@...il.com>
To:     Baoquan He <bhe@...hat.com>
Cc:     Dave Young <dyoung@...hat.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Will Deacon <will.deacon@....com>,
        Nicolas Pitre <nico@...aro.org>,
        Chao Fan <fanc.fnst@...fujitsu.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv2] x86/boot/KASLR: skip the specified crashkernel reserved region

On Fri, Mar 29, 2019 at 2:27 PM Baoquan He <bhe@...hat.com> wrote:
>
> On 03/29/19 at 01:45pm, Pingfan Liu wrote:
> > On Fri, Mar 22, 2019 at 4:34 PM Baoquan He <bhe@...hat.com> wrote:
> > >
> > > On 03/22/19 at 03:52pm, Baoquan He wrote:
> > > > On 03/22/19 at 03:43pm, Pingfan Liu wrote:
> > > > > > > +/* parse crashkernel=x@y option */
> > > > > > > +static void mem_avoid_crashkernel_simple(char *option)
> > > > > >
> > > > > > Chao ever mentioned this, I want to ask again, why does it has to be
> > > > > > xxx_simple()?
> > > > > >
> > > > > Seems that I had replied Chao's question in another email. The naming
> > > > > follows the function parse_crashkernel_simple(), as the notes above
> > > >                        ~~~~~~~~~~~~~~~~~~~~~~~~
> > > >
> > > > Sorry, I don't get.  typo?
> > >
> > > OK, I misunderstood it. We do have parse_crashkernel_simple() to handle
> > > crashkernel=size[@offset] case, to differente with other complicated
> > > cases, like crashkernel=size,[high|low],
> > >
> > > Then I am fine with this naming. Soryy about the noise.
> > >
> > > By the way, do you think if we should take care of this case:
> > > crashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset]
> > >
> > > It can also specify @offset. Not sure if it's too complicated, you may
> > > have a investigation.
> > >
> > In this case, kernel should get the total memory size info. So
> > process_e820_entries() or process_efi_entries() should be called
> > twice. One before handle_mem_options(), so crashkernel can evaluate
> > the reserved size. It is doable, and what is your opinion about the
>
> You mean calling process_e820_entries to calculate the RAM size in
> system? I may not do like that, please check what __find_max_addr() is
> doing. Did I get it?

Yes, you got my meaning. But __find_max_addr() relies on the info, fed
by e820__memblock_setup(). It also involves the iteration of all e820
entries to get the max address. No essential difference, right?