linux-kernel - Re: [PATCH V5 0/4] Fix kvm misconceives NVDIMM pages as reserved mmio

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Date:   Wed, 19 Sep 2018 18:55:05 +0800
From:   Yi Zhang <yi.z.zhang@...ux.intel.com>
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-nvdimm@...ts.01.org, pbonzini@...hat.com,
        dan.j.williams@...el.com, dave.jiang@...el.com,
        yu.c.zhang@...el.com, pagupta@...hat.com, david@...hat.com,
        jack@...e.cz, hch@....de
Cc:     linux-mm@...ck.org, rkrcmar@...hat.com, jglisse@...hat.com,
        yi.z.zhang@...el.com
Subject: Re: [PATCH V5 0/4] Fix kvm misconceives NVDIMM pages as reserved mmio

Any comments?

Hi Pankaj and Paolo,

Can we Queue this to merge list since there no other comments last 2
weeks?

Regards
Yi.

On 2018-09-08 at 02:03:02 +0800, Zhang Yi wrote:
> For device specific memory space, when we move these area of pfn to
> memory zone, we will set the page reserved flag at that time, some of
> these reserved for device mmio, and some of these are not, such as
> NVDIMM pmem.
> 
> Now, we map these dev_dax or fs_dax pages to kvm for DIMM/NVDIMM
> backend, since these pages are reserved. the check of
> kvm_is_reserved_pfn() misconceives those pages as MMIO. Therefor, we
> introduce 2 page map types, MEMORY_DEVICE_FS_DAX/MEMORY_DEVICE_DEV_DAX,
> to indentify these pages are from NVDIMM pmem. and let kvm treat these
> as normal pages.
> 
> Without this patch, Many operations will be missed due to this
> mistreatment to pmem pages. For example, a page may not have chance to
> be unpinned for KVM guest(in kvm_release_pfn_clean); not able to be
> marked as dirty/accessed(in kvm_set_pfn_dirty/accessed) etc.
> 
> V1:
> https://lkml.org/lkml/2018/7/4/91
> 
> V2:
> https://lkml.org/lkml/2018/7/10/135
> 
> V3:
> https://lkml.org/lkml/2018/8/9/17
> 
> V4:
> https://lkml.org/lkml/2018/8/22/17
> 
> V5:
> [PATCH V3 1/4] Reviewed-by: David / Acked-by: Pankaj
> [PATCH V3 2/4] Reviewed-by: Jan
> [PATCH V3 3/4] Acked-by: Jan
> [PATCH V3 4/4] Added "Acked-by: Pankaj", Added in-line comments: Dave
> 
> Zhang Yi (4):
>   kvm: remove redundant reserved page check
>   mm: introduce memory type MEMORY_DEVICE_DEV_DAX
>   mm: add a function to differentiate the pages is from DAX device
>     memory
>   kvm: add a check if pfn is from NVDIMM pmem.
> 
>  drivers/dax/pmem.c       |  1 +
>  include/linux/memremap.h |  8 ++++++++
>  include/linux/mm.h       | 12 ++++++++++++
>  virt/kvm/kvm_main.c      | 24 ++++++++++++++++--------
>  4 files changed, 37 insertions(+), 8 deletions(-)
> 
> -- 
> 2.7.4
>