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    SubjectRe: [PATCH 10/26] x86-64, NUMA: Move apicid to numa mapping initialization from amd_scan_nodes() to amd_numa_init()
    On 02/15/2011 12:36 PM, Tejun Heo wrote:
    ...
    >>
    >> Hi Tejun, while you at it, it seems apicid_base conditional assignment is
    >> redundant here (boot_cpu_physical_apicid is unsigned int) so we might have
    >> something like
    >>
    >> apicid_start = boot_cpu_physical_apicid;
    >> apicid_end = apicid_start + cores;
    >>
    >> for_each_node_mask(i, cpu_nodes_parsed) {
    >> for (j = apicid_start; j< apicid_end; j++)
    >> set_apicid_to_node((i<< bits) + j, i);
    >> }
    >
    > Right, I think the intention there was
    >
    > if (boot_cpu_physical_apicid == -1U)
    >
    > because that's the initial value and we don't really want to index the
    > apicid nid table with -1U. Care to send a patch? I'm gonna have to
    > rebase anyway and can put the patch at the front.
    >
    > Thanks.
    >

    Hi Tejun again :) I've looked some more and if I'm not missing something
    (Yinghai?) the code is broken in another way. We might have AMD system
    with corrupted MADT table so boot_cpu_physical_apicid remains =-1U
    and then we better BUG_ON instead of possible access of out-of-range
    __apicid_to_node array. If MADT is parsed successfully boot_cpu_physical_apicid
    will have correct value. So I think we rather should add something like the
    patch below. Again better Yinghai check it first so I would not _miss_ the
    point that such situation is impossible at all. (And if I'm right we need to
    check for set_apicid_to_node(apicid, ) never exceed MAX_LOCAL_APIC as well.

    Yinghai am I missing something?

    --
    Cyrill

    ---
    x86, numa: amd -- Check for screwed MADT table

    In case if MADT table is corrupted we might end up
    with boot_cpu_physical_apicid = -1U, corebits > 0 and
    get out of __apicid_to_node array bound access. Check for
    boot_cpu_physical_apicid being not default value.

    Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
    ---
    arch/x86/mm/amdtopology_64.c | 7 ++++++-
    1 file changed, 6 insertions(+), 1 deletion(-)

    Index: linux-2.6.git/arch/x86/mm/amdtopology_64.c
    =====================================================================
    --- linux-2.6.git.orig/arch/x86/mm/amdtopology_64.c
    +++ linux-2.6.git/arch/x86/mm/amdtopology_64.c
    @@ -271,9 +271,14 @@ int __init amd_scan_nodes(void)
    bits = boot_cpu_data.x86_coreid_bits;
    cores = (1<<bits);
    apicid_base = 0;
    +
    /* get the APIC ID of the BSP early for systems with apicid lifting */
    early_get_boot_cpu_id();
    - if (boot_cpu_physical_apicid > 0) {
    + if (boot_cpu_physical_apicid == -1U || ) {
    + pr_err("BAD APIC ID: %02x, NUMA node scaning canceled\n",
    + boot_cpu_physical_apicid);
    + return -1;
    + } else if (boot_cpu_physical_apicid > 0) {
    pr_info("BSP APIC ID: %02x\n", boot_cpu_physical_apicid);
    apicid_base = boot_cpu_physical_apicid;
    }

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