Re: [PATCH v12 07/29] HMM: add per mirror page table v4.

[John Hubbard]

On Tue, 8 Mar 2016, JÃrÃme Glisse wrote:

> This patch add the per mirror page table. It also propagate CPU page
> table update to this per mirror page table using mmu_notifier callback.
> All update are contextualized with an HMM event structure that convey
> all information needed by device driver to take proper actions (update
> its own mmu to reflect changes and schedule proper flushing).
> 
> Core HMM is responsible for updating the per mirror page table once
> the device driver is done with its update. Most importantly HMM will
> properly propagate HMM page table dirty bit to underlying page.
> 
> Changed since v1:
>   - Removed unused fence code to defer it to latter patches.
> 
> Changed since v2:
>   - Use new bit flag helper for mirror page table manipulation.
>   - Differentiate fork event with HMM_FORK from other events.
> 
> Changed since v3:
>   - Get rid of HMM_ISDIRTY and rely on write protect instead.
>   - Adapt to HMM page table changes
> 
> Signed-off-by: JÃrÃme Glisse <jglisse@xxxxxxxxxx>
> Signed-off-by: Sherry Cheung <SCheung@xxxxxxxxxx>
> Signed-off-by: Subhash Gutti <sgutti@xxxxxxxxxx>
> Signed-off-by: Mark Hairgrove <mhairgrove@xxxxxxxxxx>
> Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
> Signed-off-by: Jatin Kumar <jakumar@xxxxxxxxxx>
> ---
>  include/linux/hmm.h |  83 ++++++++++++++++++++
>  mm/hmm.c            | 221 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 304 insertions(+)
> 
> diff --git a/include/linux/hmm.h b/include/linux/hmm.h
> index b559c0b..5488fa9 100644
> --- a/include/linux/hmm.h
> +++ b/include/linux/hmm.h
> @@ -46,6 +46,7 @@
>  #include <linux/mmu_notifier.h>
>  #include <linux/workqueue.h>
>  #include <linux/mman.h>
> +#include <linux/hmm_pt.h>
>  
>  
>  struct hmm_device;
> @@ -53,6 +54,38 @@ struct hmm_mirror;
>  struct hmm;
>  
>  
> +/*
> + * hmm_event - each event is described by a type associated with a struct.
> + */
> +enum hmm_etype {
> +	HMM_NONE = 0,
> +	HMM_FORK,
> +	HMM_MIGRATE,
> +	HMM_MUNMAP,
> +	HMM_DEVICE_RFAULT,
> +	HMM_DEVICE_WFAULT,

Hi Jerome,

Just a tiny thing I noticed, while connecting HMM to NVIDIA's upcoming 
device driver: the last two enum items above should probably be named 
like this:

	HMM_DEVICE_READ_FAULT,
	HMM_DEVICE_WRITE_FAULT,

instead of _WFAULT / _RFAULT. (Earlier code reviewers asked for more 
clarity on these types of names.)

thanks,
John Hubbard

> +	HMM_WRITE_PROTECT,
> +};
> +