Re: [PATCH 1/2] x86 boot: add E820_RESVD_KERN

["Yinghai Lu" <yhlu.kernel@gmail.com>]

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On Mon, Jun 30, 2008 at 12:51 AM, Huang, Ying <ying.huang@intel.com> wrote:> On Mon, 2008-06-30 at 00:34 -0700, Yinghai Lu wrote:>> On Mon, Jun 30, 2008 at 12:03 AM, Huang, Ying <ying.huang@intel.com> wrote:>> > 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@intel.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@gmail.com> wrote:>> >> >> > On Thu, Jun 26, 2008 at 12:48 AM, Huang, Ying <ying.huang@intel.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().>>>> what is "other memory area"? returned from find_e820_area? no one use that yet.>> I mean memory area reserved with reserved_early() or e820_update_range()> before reserve_setup_data() is called.
before parse_setup_data, reserve_early is called for1. kernel text/data/bss + initial pgt2. ramdisk3. ebdae820_update_range is not called.at this time early_res have RAM reserved by kernel.
then setup_memory_map is called, so e820 have some ranges...directlyfrom e820 table
next need to call parse_setup_datait will add some entries in e820
then reserve_setup_data is called, it will use e820_update_range toreserve setup_data itself directly in e820
...
>> And because there is no conflict check in e820_update_range(), what to> deal with potential conflict between setup_data and other memory area> regardless which one is reserved earlier?
find_e820_area will make sure it only find ram from e820 and it is notconflict with early_res

>>> Another issue related:>> Because some memmap entries are available via extended E820 memmap> (SETUP_E820_EXT), it is not strictly safe to use e820_update_range()> between setup_memory_map() and parse_setup_data(). It may be better to> parse extended E820 memmap right after setup_memory_map().
will look at the code again..
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