Re: [PATCH v2] KVM: cleanup {kvm_vm_ioctl, kvm}_get_dirty_log()

[Takuya Yoshikawa]

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

Oh, for such a tiny comment.

Signed-off-by: Xiao Guangrong <xiaoguangr...@cn.fujitsu.com>
---
 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

What I said was just you may be able to use bitmap_empty() instead of

> -  for (i = 0; !is_dirty && i < n/sizeof(long); i++)
> -          is_dirty = memslot->dirty_bitmap[i];

for x86's code too, if your patch for kvm_get_dirty_log() was correct.

@@ -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;
-
        n = ALIGN(memslot->npages, BITS_PER_LONG) / 8;

r = -ENOMEM;

@@ -2668,9 +2663,6 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
                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;
@@ -2694,8 +2686,7 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
        }

r = 0;

-       if (copy_to_user(log->dirty_bitmap, dirty_bitmap, n))
-               r = -EFAULT;
+
 out_free:
        vfree(dirty_bitmap);
 out:
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
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);

r = -EFAULT;

        if (copy_to_user(log->dirty_bitmap, memslot->dirty_bitmap, n))

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