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

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Date:   Tue, 18 Sep 2018 22:43:06 -0400 (EDT)
From:   Pankaj Gupta <pagupta@...hat.com>
To:     Yi Zhang <yi.z.zhang@...ux.intel.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-nvdimm@...ts.01.org, pbonzini@...hat.com,
        dan j williams <dan.j.williams@...el.com>,
        dave jiang <dave.jiang@...el.com>,
        yu c zhang <yu.c.zhang@...el.com>, david@...hat.com,
        jack@...e.cz, hch@....de, linux-mm@...ck.org, rkrcmar@...hat.com,
        jglisse@...hat.com, yi z zhang <yi.z.zhang@...el.com>
Subject: Re: [PATCH V5 0/4] Fix kvm misconceives NVDIMM pages as reserved
 mmio


Hello Yi,

> Any comments?
> 
> Hi Pankaj and Paolo,

I am just helping with the review. Paolo & Dan probably will decide.

Thanks,
Pankaj

> 
> 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
> > 
>