Now that mmu_lock is held only inside kvm_mmu_write_protect_pt_masked(),
we can do __put_user() for copying each 64/32 dirty bits to user-space.
This eliminates the need to copy the whole bitmap to an extra buffer and
the resulting code is much more cache friendly than before.
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@xxxxxxxxxxxxx>
Cc: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/x86.c | 18 ++++++++----------
virt/kvm/kvm_main.c | 6 +-----
2 files changed, 9 insertions(+), 15 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1d1f6df..79e8ad0 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3522,7 +3522,7 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
struct kvm_memory_slot *memslot;
unsigned long n, i;
unsigned long *dirty_bitmap;
- unsigned long *dirty_bitmap_buffer;
+ unsigned long __user *p_user;
bool is_dirty = false;
mutex_lock(&kvm->slots_lock);
@@ -3539,11 +3539,12 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
goto out;
n = kvm_dirty_bitmap_bytes(memslot);
+ r = -EFAULT;
+ if (clear_user(log->dirty_bitmap, n))
+ goto out;
- dirty_bitmap_buffer = dirty_bitmap + n / sizeof(long);
- memset(dirty_bitmap_buffer, 0, n);
-
- for (i = 0; i < n / sizeof(long); i++) {
+ p_user = (unsigned long __user *)log->dirty_bitmap;
+ for (i = 0; i < n / sizeof(long); i++, p_user++) {
unsigned long mask;
gfn_t offset;
@@ -3553,7 +3554,8 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
is_dirty = true;
mask = xchg(&dirty_bitmap[i], 0);
- dirty_bitmap_buffer[i] = mask;
+ if (__put_user(mask, p_user))
+ goto out;
offset = i * BITS_PER_LONG;
kvm_mmu_write_protect_pt_masked(kvm, memslot, offset, mask);
@@ -3561,10 +3563,6 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
if (is_dirty)
kvm_flush_remote_tlbs(kvm);
- r = -EFAULT;
- if (copy_to_user(log->dirty_bitmap, dirty_bitmap_buffer, n))
- goto out;
-
r = 0;
out:
mutex_unlock(&kvm->slots_lock);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index bf040c4..c919f58 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -626,14 +626,10 @@ static int kvm_vm_release(struct inode *inode, struct file *filp)
return 0;
}
-/*
- * Allocation size is twice as large as the actual dirty bitmap size.
- * See x86's kvm_vm_ioctl_get_dirty_log() why this is needed.
- */
static int kvm_create_dirty_bitmap(struct kvm_memory_slot *memslot)
{
#ifndef CONFIG_S390
- unsigned long dirty_bytes = 2 * kvm_dirty_bitmap_bytes(memslot);
+ unsigned long dirty_bytes = kvm_dirty_bitmap_bytes(memslot);
memslot->dirty_bitmap = kvm_kvzalloc(dirty_bytes);
if (!memslot->dirty_bitmap)
--
1.7.9.5
--
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