On Wed, Mar 17, 2010 at 03:49:19PM +0800, Xiao Guangrong wrote:
> Using bitmap_empty() to see whether memslot->dirty_bitmap is empty
>
> Changlog:
> cleanup x86 specific kvm_vm_ioctl_get_dirty_log() and fix a local
> parameter's type address Takuya Yoshikawa's suggestion
>
> Signed-off-by: Xiao Guangrong <[email protected]>
> ---
> arch/x86/kvm/x86.c | 17 ++++-------------
> virt/kvm/kvm_main.c | 7 ++-----
> 2 files changed, 6 insertions(+), 18 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index bcf52d1..e6cbbd4 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2644,22 +2644,17 @@ 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, n, i;
> + int r, n, is_dirty = 0;
> struct kvm_memory_slot *memslot;
> - unsigned long is_dirty = 0;
> unsigned long *dirty_bitmap = NULL;
>
> mutex_lock(&kvm->slots_lock);
>
> - r = -EINVAL;
> - if (log->slot >= KVM_MEMORY_SLOTS)
> + r = kvm_get_dirty_log(kvm, log, &is_dirty);
> + if (r)
> goto out;
>
> memslot = &kvm->memslots->memslots[log->slot];
> - r = -ENOENT;
> - if (!memslot->dirty_bitmap)
> - goto out;
> -
Its different because the user copy must be done after the
SRCU assignment.
> index bcd08b8..b08a7de 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -767,9 +767,7 @@ int kvm_get_dirty_log(struct kvm *kvm,
> struct kvm_dirty_log *log, int *is_dirty)
> {
> struct kvm_memory_slot *memslot;
> - int r, i;
> - int n;
> - unsigned long any = 0;
> + int r, n, any = 0;
>
> r = -EINVAL;
> if (log->slot >= KVM_MEMORY_SLOTS)
> @@ -782,8 +780,7 @@ int kvm_get_dirty_log(struct kvm *kvm,
>
> n = ALIGN(memslot->npages, BITS_PER_LONG) / 8;
>
> - for (i = 0; !any && i < n/sizeof(long); ++i)
> - any = memslot->dirty_bitmap[i];
> + any = !bitmap_empty(memslot->dirty_bitmap, memslot->npages);
The opencoded version should be faster in comparison to __bitmap_empty
because the dirty bitmaps are always unsigned long aligned (and also
there's a function call).
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