Re: [Qemu-devel] [RFC PATCH v3 3/3] VFIO Type1 IOMMU change: to support with iommu and without iommu

[Jike Song]

On 05/13/2016 04:31 PM, Neo Jia wrote:
> On Fri, May 13, 2016 at 07:45:14AM +0000, Tian, Kevin wrote:
>>
>> We use page tracking framework, which is newly added to KVM recently,
>> to mark RAM pages as read-only so write accesses are intercepted to 
>> device model.
> 
> Yes, I am aware of that patchset from Guangrong. So far the interface are all
> requiring struct *kvm, copied from https://lkml.org/lkml/2015/11/30/644
> 
> - kvm_page_track_add_page(): add the page to the tracking pool after
>   that later specified access on that page will be tracked
> 
> - kvm_page_track_remove_page(): remove the page from the tracking pool,
>   the specified access on the page is not tracked after the last user is
>   gone
> 
> void kvm_page_track_add_page(struct kvm *kvm, gfn_t gfn,
>                 enum kvm_page_track_mode mode);
> void kvm_page_track_remove_page(struct kvm *kvm, gfn_t gfn,
>                enum kvm_page_track_mode mode);
> 
> Really curious how you are going to have access to the struct kvm *kvm, or you
> are relying on the userfaultfd to track the write faults only as part of the
> QEMU userfault thread?
>

Hi Neo,

For the vGPU used as a device for KVM guest, there will be interfaces
wrapped or implemented in KVM layer, as a rival thing diverted from
the interfaces for Xen. That is where the KVM related code supposed to be.

--
Thanks,
Jike