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    SubjectRe: [PATCH 1/2 v2] x86: add max_addr boot option
    (2012/06/13 12:29), H. Peter Anvin wrote:
    > On 06/12/2012 07:21 PM, Kamezawa Hiroyuki wrote:
    >>
    >> But now, we know mem= boot option is buggy....it acts as max_addr=
    >> option, we have concerns that 'someone may fix mem= option as sane as ia64. because
    >> it's buggy".
    >>
    >> We'd like to fix mem= boot option by ourselves and preserve old behavior
    >> with max_addr= boot option, which ia64 has.
    >>
    >
    > Now I'm *really* confused.
    >
    > Realistically, there is no point in the old mem= behavior of assuming a
    > contiguous chunk of memory up to that point; it simply doesn't match how
    > modern hardware is constructed. Your notion that ia64 is "sane" is
    > probably more of "outdated" in my opinion.
    >
    > As such, the current behavior for mem= seems like the right thing and
    > the change was intentional (not to mention has been in place since
    > kernel 2.5.65, back in 2003); it also solves your requirements. If you
    > are concerned about it, it would make more sense to make sure it is
    > documented as intentional.
    >
    > In fact, it looks like IA64 introduced a divergence when the max_addr=
    > patch was introduced in 2004. You're basically proposing the same
    > divergence for x86 now; talk about having the tail wag the dog.
    >
    > Sorry. NAK.
    >

    Hmm, them, it's ok to post a patch for fixing kernel-param

    mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
    Amount of memory to be used when the kernel is not able
    to see the whole system memory or for test.
    [X86-32] Use together with memmap= to avoid physical
    address space collisions. Without memmap= PCI devices
    could be placed at addresses belonging to unused RAM.

    to explain 'work as limiting max address' and implementing current mem= behavior
    in x86-64/efi code ?

    Thanks,
    -Kame






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