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SubjectRe: [PATCH V3 3/4] mm: add a function to differentiate the pages is from DAX device memory

>
> DAX driver hotplug the device memory and move it to memory zone, these
> pages will be marked reserved flag, however, some other kernel componet
> will misconceive these pages are reserved mmio (ex: we map these dev_dax
> or fs_dax pages to kvm for DIMM/NVDIMM backend). Together with the type
> MEMORY_DEVICE_FS_DAX, we can use is_dax_page() to differentiate the pages
> is DAX device memory or not.
>
> Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com>
> Signed-off-by: Zhang Yu <yu.c.zhang@linux.intel.com>
> ---
> include/linux/mm.h | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 68a5121..de5cbc3 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -889,6 +889,13 @@ static inline bool is_device_public_page(const struct
> page *page)
> page->pgmap->type == MEMORY_DEVICE_PUBLIC;
> }
>
> +static inline bool is_dax_page(const struct page *page)
> +{
> + return is_zone_device_page(page) &&
> + (page->pgmap->type == MEMORY_DEVICE_FS_DAX ||
> + page->pgmap->type == MEMORY_DEVICE_DEV_DAX);
> +}

I think question from Dan for KVM VM with 'MEMORY_DEVICE_PUBLIC' still holds?
I am also interested to know if there is any use-case.

Thanks,
Pankaj

> +
> #else /* CONFIG_DEV_PAGEMAP_OPS */
> static inline void dev_pagemap_get_ops(void)
> {
> @@ -912,6 +919,11 @@ static inline bool is_device_public_page(const struct
> page *page)
> {
> return false;
> }
> +
> +static inline bool is_dax_page(const struct page *page)
> +{
> + return false;
> +}
> #endif /* CONFIG_DEV_PAGEMAP_OPS */
>
> static inline void get_page(struct page *page)
> --
> 2.7.4
>
>

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