linux-kernel - Re: [PATCH 1/2] x86 boot: add E820_RESVD

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Date:	Mon, 30 Jun 2008 15:03:54 +0800
From:	"Huang, Ying" <ying.huang@...el.com>
To:	Yinghai Lu <yhlu.kernel@...il.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, andi@...stfloor.org,
	mingo@...hat.com, tglx@...utronix.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] x86 boot: add E820_RESVD_KERN

On Fri, 2008-06-27 at 15:05 -0700, Yinghai Lu wrote:
> On Thu, Jun 26, 2008 at 7:48 PM, Huang, Ying <ying.huang@...el.com> wrote:
> > On Thu, 2008-06-26 at 19:22 -0700, Yinghai Lu wrote:
> >> On Thu, Jun 26, 2008 at 2:47 AM, Yinghai Lu <yhlu.kernel@...il.com> wrote:
> >> > On Thu, Jun 26, 2008 at 12:48 AM, Huang, Ying <ying.huang@...el.com> wrote:
> >> >> On Thu, 2008-06-26 at 00:25 -0700, Yinghai Lu wrote:
> >> >> [...]
> >> >>> >                if (pfn >= limit_pfn)
> >> >>> > @@ -977,7 +978,7 @@ u64 __init early_reserve_e820(u64 startt
> >> >>> >                return 0;
> >> >>> >
> >> >>> >        addr = round_down(start + size - sizet, align);
> >> >>> > -       e820_update_range(addr, sizet, E820_RAM, E820_RESERVED);
> >> >>> > +       e820_update_range(addr, sizet, E820_RAM, E820_RESVD_KERN);
> >> >>>
> >> >>> this line is not needed.
> >> >>
> >> >> Why? Memory reserved by early_rserved_e820 should not be saved during
> >> >> hibernation? shoudl not be saved by kdump?
> >> >>
> >
> > Can you tell me why this line is not needed?
> >
> > [...]
> >> some like the attach patch...
> >>
> >> you still can merge parse_setup_data parse_e820_ext
> >> also entries in parse_e820_ext is not initialized..., __copy_e820_map
> >> will do nothing.
> >
> > OK. Because some E820 entries are available after parse_setup_data(),
> > it is better to call reserve_setup_data() after calling
> > parse_setup_data() if update_e820_range() is used instead of
> > reserve_early().
> 
> please modify it and test on your platforms then submit to Ingo..

It seems that there is an issue:

- If parse_setup_data() is called before reserve_setup_data(), and there
is a conflict between memory area used by setup_data and other memory
area, it is possible that the contents of setup_data is changed. So that
system may panic before reporting memory area conflict. And it seems
that memory area conflict is not checked by e820_update_range().

So maybe it is better to use reserve_early() instead of
e820_update_range() for setup_data.

Best Regards,
Huang Ying

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