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    Subject[PATCH] KVM: x86/mmu: Grab nx_lpage_splits as an unsigned long before division
    From
    Snapshot kvm->stats.nx_lpage_splits into a local unsigned long to avoid
    64-bit division on 32-bit kernels. Casting to an unsigned long is safe
    because the maximum number of shadow pages, n_max_mmu_pages, is also an
    unsigned long, i.e. KVM will start recycling shadow pages before the
    number of splits can exceed a 32-bit value.

    ERROR: modpost: "__udivdi3" [arch/x86/kvm/kvm.ko] undefined!

    Fixes: 7ee093d4f3f5 ("KVM: switch per-VM stats to u64")
    Signed-off-by: Sean Christopherson <seanjc@google.com>
    ---
    arch/x86/kvm/mmu/mmu.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
    index 720ceb0a1f5c..7d3e57678d34 100644
    --- a/arch/x86/kvm/mmu/mmu.c
    +++ b/arch/x86/kvm/mmu/mmu.c
    @@ -6043,6 +6043,7 @@ static int set_nx_huge_pages_recovery_ratio(const char *val, const struct kernel

    static void kvm_recover_nx_lpages(struct kvm *kvm)
    {
    + unsigned long nx_lpage_splits = kvm->stat.nx_lpage_splits;
    int rcu_idx;
    struct kvm_mmu_page *sp;
    unsigned int ratio;
    @@ -6054,7 +6055,7 @@ static void kvm_recover_nx_lpages(struct kvm *kvm)
    write_lock(&kvm->mmu_lock);

    ratio = READ_ONCE(nx_huge_pages_recovery_ratio);
    - to_zap = ratio ? DIV_ROUND_UP(kvm->stat.nx_lpage_splits, ratio) : 0;
    + to_zap = ratio ? DIV_ROUND_UP(nx_lpage_splits, ratio) : 0;
    for ( ; to_zap; --to_zap) {
    if (list_empty(&kvm->arch.lpage_disallowed_mmu_pages))
    break;
    --
    2.32.0.272.g935e593368-goog
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