Re: [PATCH v12 2/6] KVM: Add generic support for dirty page logging

[Mario Smarduch <m.smarduch@samsung.com>]

On 11/06/2014 02:14 AM, Paolo Bonzini wrote:
> 
> 
> On 06/11/2014 00:05, Mario Smarduch wrote:
>> On 11/05/2014 08:09 AM, Paolo Bonzini wrote:
>>>
>>>
>>> On 01/11/2014 11:12, James Hogan wrote:
>>>> AFAICT all of the arch implementations of kvm_vm_ioctl_get_dirty_log()
>>>> except x86 and ppc hv (i.e. ia60, mips, ppc pv, s390) already make use
>>>> of the existing generic function kvm_get_dirty_log() to help implement
>>>> their kvm_vm_ioctl_get_dirty_log functions, which all look pretty
>>>> similar now except for TLB flushing.
>>>>
>>>> Would they not be a better base for a generic
>>>> kvm_vm_ioctl_get_dirty_log()?
>>>>
>>>> It feels a bit wrong to add a generic higher level function which
>>>> doesn't make use of the existing generic lower level abstraction.
>>>>
>>>> (Appologies if this has already been brought up in previous versions of
>>>> the patchset, I haven't been tracking them).
>>>
>>> I agree that we should make the interface look more like
>>> kvm_get_dirty_log().  Here the steps are:
>>>
>>> + *   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.
>>
>> Hi Paolo,
>>   thanks for breaking it down between generic/architecture layers,
>> helps a lot. Initially I thought we could get TLB flushing to
>> generic layer, previous x86 version worked for ARM. But looking
>> deeper other architectures either use non-generic flush or none
>> at all. Right now we would have x86, ARM, IA64 using generic TLB flush.
>> I'll restructure for another version.
> 
> I'll test the swap between 3 and 4 above, and send it to the list.  Feel
> free to include it in v13, so that it gets back to me via Christoffer
> and Marc.
> 
> Paolo
> 

Ok, will do. So it would be kvm/kvm/x86 and 4 armv7 patches.

Mario