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    Subject[PATCH 32/40] KVM: use SRCU for dirty log
    Date
    From: Marcelo Tosatti <mtosatti@redhat.com>

    Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
    ---
    arch/x86/kvm/x86.c | 49 +++++++++++++++++++++++++++++++++++++++++--------
    1 files changed, 41 insertions(+), 8 deletions(-)

    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index 6a795be..2d7c040 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -2416,27 +2416,60 @@ static int kvm_vm_ioctl_reinject(struct kvm *kvm,
    int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
    struct kvm_dirty_log *log)
    {
    - int r;
    - int n;
    + int r, n, i;
    struct kvm_memory_slot *memslot;
    - int is_dirty = 0;
    + unsigned long is_dirty = 0;
    + unsigned long *dirty_bitmap = NULL;

    down_write(&kvm->slots_lock);

    - r = kvm_get_dirty_log(kvm, log, &is_dirty);
    - if (r)
    + r = -EINVAL;
    + if (log->slot >= KVM_MEMORY_SLOTS)
    + goto out;
    +
    + memslot = &kvm->memslots->memslots[log->slot];
    + r = -ENOENT;
    + if (!memslot->dirty_bitmap)
    + goto out;
    +
    + n = ALIGN(memslot->npages, BITS_PER_LONG) / 8;
    +
    + r = -ENOMEM;
    + dirty_bitmap = vmalloc(n);
    + if (!dirty_bitmap)
    goto out;
    + memset(dirty_bitmap, 0, n);
    +
    + for (i = 0; !is_dirty && i < n/sizeof(long); i++)
    + is_dirty = memslot->dirty_bitmap[i];

    /* If nothing is dirty, don't bother messing with page tables. */
    if (is_dirty) {
    + struct kvm_memslots *slots, *old_slots;
    +
    spin_lock(&kvm->mmu_lock);
    kvm_mmu_slot_remove_write_access(kvm, log->slot);
    spin_unlock(&kvm->mmu_lock);
    - memslot = &kvm->memslots->memslots[log->slot];
    - n = ALIGN(memslot->npages, BITS_PER_LONG) / 8;
    - memset(memslot->dirty_bitmap, 0, n);
    +
    + slots = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);
    + if (!slots)
    + goto out_free;
    +
    + memcpy(slots, kvm->memslots, sizeof(struct kvm_memslots));
    + slots->memslots[log->slot].dirty_bitmap = dirty_bitmap;
    +
    + old_slots = kvm->memslots;
    + rcu_assign_pointer(kvm->memslots, slots);
    + synchronize_srcu_expedited(&kvm->srcu);
    + dirty_bitmap = old_slots->memslots[log->slot].dirty_bitmap;
    + kfree(old_slots);
    }
    +
    r = 0;
    + if (copy_to_user(log->dirty_bitmap, dirty_bitmap, n))
    + r = -EFAULT;
    +out_free:
    + vfree(dirty_bitmap);
    out:
    up_write(&kvm->slots_lock);
    return r;
    --
    1.6.5.3


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