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    Subject[PATCH for 2.6.22] [1/10] i386: bug in i386 MTRR initialization
    Date

    From: Andrea Righi <righiandr@users.sourceforge.net>
    BUG: at include/linux/slub_def.h:77 kmalloc_index()
    [<c0168eb0>] get_slab+0x1d0/0x260
    [<c0169056>] __kmalloc+0x16/0x70
    [<c042b0ff>] sysenter_setup+0x6f/0x330
    [<c010baed>] mtrr_bp_init+0xcd/0x270
    [<c041a480>] unknown_bootoption+0x0/0x250
    [<c041a480>] unknown_bootoption+0x0/0x250
    [<c0423f78>] check_bugs+0x8/0x160
    [<c01a644c>] proc_sys_init+0xc/0x30
    [<c041a8ef>] start_kernel+0x21f/0x2b0
    [<c041a480>] unknown_bootoption+0x0/0x250
    =======================

    Reproduced running 2.6.22-rc2 (using SLUB) in a virtual machine with qemu 0.9.0
    + kqemu 1.3.0pre11. It occurs only using "-kernel-kqemu" option (full
    virtualization mode).

    In this case mtrr is supported by the real cpu, but no mtrr range is found,
    resulting in a kmalloc(0, GFP_KERNEL) in get_mtrr_state() and init_table().

    I don't know if it's an incorrect behaviour of qemu in the mtrr emulation, but I
    think it should be handled properly.

    Signed-off-by: Andrea Righi <a.righi@cineca.it>
    Signed-off-by: Andi Kleen <ak@suse.de>

    ---
    arch/i386/kernel/cpu/mtrr/generic.c | 3 +++
    arch/i386/kernel/cpu/mtrr/main.c | 5 +++++
    2 files changed, 8 insertions(+)

    Index: linux/arch/i386/kernel/cpu/mtrr/generic.c
    ===================================================================
    --- linux.orig/arch/i386/kernel/cpu/mtrr/generic.c
    +++ linux/arch/i386/kernel/cpu/mtrr/generic.c
    @@ -84,6 +84,9 @@ void get_mtrr_state(void)
    struct mtrr_var_range *vrs;
    unsigned lo, dummy;

    + if (!num_var_ranges)
    + return;
    +
    if (!mtrr_state.var_ranges) {
    mtrr_state.var_ranges = kmalloc(num_var_ranges * sizeof (struct mtrr_var_range),
    GFP_KERNEL);
    Index: linux/arch/i386/kernel/cpu/mtrr/main.c
    ===================================================================
    --- linux.orig/arch/i386/kernel/cpu/mtrr/main.c
    +++ linux/arch/i386/kernel/cpu/mtrr/main.c
    @@ -120,6 +120,11 @@ static void __init init_table(void)
    {
    int i, max;

    + if (!num_var_ranges) {
    + printk(KERN_ERR "mtrr: no MTRR range found.\n");
    + return;
    + }
    +
    max = num_var_ranges;
    if ((usage_table = kmalloc(max * sizeof *usage_table, GFP_KERNEL))
    == NULL) {
    -
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