linux-kernel - Re: [PATCH V2 0/4] Fix kvm misconceives NVDIMM pages as reserved mmio

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Date:   Sat, 21 Jul 2018 00:24:41 +0800
From:   "Zhang,Yi" <yi.z.zhang@...ux.intel.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-nvdimm@...ts.01.org,
        dan.j.williams@...el.com, jack@...e.cz, hch@....de,
        yu.c.zhang@...el.com, dave.jiang@...el.com
Cc:     linux-mm@...ck.org, rkrcmar@...hat.com, yi.z.zhang@...el.com
Subject: Re: [PATCH V2 0/4] Fix kvm misconceives NVDIMM pages as reserved mmio

Thanks Paolo, let's wait Jan&Dan 's comments.

Thank you, Paolo.

Regards
Yi

On 2018年07月20日 16:32, Paolo Bonzini wrote:
> On 20/07/2018 16:11, Zhang,Yi wrote:
>> Added Jiang,Dave,
>>
>> Ping for further review, comments.
> I need an Acked-by from the MM people to merge this.  Jan, Dan?
>
> Paolo
>
>> Thanks All
>>
>> Regards
>> Yi.
>>
>>
>> On 2018年07月11日 01:01, 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:
>>> *Add documentation for MEMORY_DEVICE_DEV_DAX memory type in comment block
>>> *Add is_dax_page() in mm.h to differentiate the pages is from DAX device.
>>> *Remove the function kvm_is_nd_pfn().
>>>
>>> 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 |  9 +++++++++
>>>  include/linux/mm.h       | 12 ++++++++++++
>>>  virt/kvm/kvm_main.c      | 16 ++++++++--------
>>>  4 files changed, 30 insertions(+), 8 deletions(-)
>>>
>>