Re: [PATCH v13 3/7] KVM: x86: flush TLBs last before returning from KVM_GET_DIRTY_LOG

Paolo Bonzini
2014-11-07T07:44:05Z

On 07/11/2014 01:40, Mario Smarduch wrote:
> In the next patches, we will move parts of x86's kvm_vm_ioctl_get_dirty_log
> implementation to generic code; leave the arch-specific code at the end,
> similar to the existing generic function kvm_get_dirty_log.
>
> Reviewed-by: Mario Smarduch <m.smarduch@samsung.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

You should have a "Signed-off-by: Mario Smarduch ..." here, and you
should also add my authorship. You can do the latter with "git rebase
-i", adding

x git commit --amend -C HEAD --author 'Paolo Bonzini <pbonzini@redhat.com>'

after this patch. If you're using a patch queue instead (quilt or
similar) you can just edit the "From" line in the patch.

I guess if you reply to the patch with just

Signed-off-by: Mario Smarduch <m.smarduch@samsung.com>

the ARM maintainers can do the above for you, if there's no need for
a v14.

I'll send an eighth patch to actually switch x86 to the new function.
Again, the maintainers can apply it in the right place, but please
include it yourself if you have to do a v14.

Thanks,

Paolo

> ---
> arch/x86/kvm/x86.c | 22 ++++++++++------------
> 1 file changed, 10 insertions(+), 12 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 8f1e22d..dc8e66b 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3606,13 +3606,13 @@ static int kvm_vm_ioctl_reinject(struct kvm *kvm,
> *
> * 1. Take a snapshot of the bit and clear it if needed.
> * 2. Write protect the corresponding page.
> - * 3. Flush TLB's if needed.
> - * 4. Copy the snapshot to the userspace.
> + * 3. Copy the snapshot to the userspace.
> + * 4. Flush TLB's if needed.
> *
> - * Between 2 and 3, the guest may write to the page using the remaining TLB
> - * entry. This is not a problem because the page will be reported dirty at
> - * step 4 using the snapshot taken before and step 3 ensures that successive
> - * writes will be logged for the next call.
> + * Between 2 and 4, the guest may write to the page using the remaining TLB
> + * entry. This is not a problem because the page is reported dirty using
> + * the snapshot taken before and step 4 ensures that writes done after
> + * exiting to userspace will be logged for the next call.
> */
> int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
> {
> @@ -3661,6 +3661,10 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
>
> spin_unlock(&kvm->mmu_lock);
>
> + r = 0;
> + if (copy_to_user(log->dirty_bitmap, dirty_bitmap_buffer, n))
> + r = -EFAULT;
> +
> /* See the comments in kvm_mmu_slot_remove_write_access(). */
> lockdep_assert_held(&kvm->slots_lock);
>
> @@ -3670,12 +3674,6 @@ 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);
> return r;
>