linux-kernel - Re: [PATCH V4 4/4] kvm: add a check if pfn is from NVDIMM pmem.

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Message-ID: <20180831163941.GA1220@tiger-server>
Date:   Sat, 1 Sep 2018 00:39:42 +0800
From:   Yi Zhang <yi.z.zhang@...ux.intel.com>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     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, linux-mm@...ck.org, rkrcmar@...hat.com,
        jglisse@...hat.com, yi.z.zhang@...el.com
Subject: Re: [PATCH V4 4/4] kvm: add a check if pfn is from NVDIMM pmem.

On 2018-08-30 at 12:07:11 -0700, Dave Hansen wrote:
> On 08/22/2018 03:58 AM, Zhang Yi wrote:
> >  bool kvm_is_reserved_pfn(kvm_pfn_t pfn)
> >  {
> > -	if (pfn_valid(pfn))
> > -		return PageReserved(pfn_to_page(pfn));
> > +	struct page *page;
> > +
> > +	if (pfn_valid(pfn)) {
> > +		page = pfn_to_page(pfn);
> > +		return PageReserved(page) && !is_dax_page(page);
> > +	}
> 
> This is in desperate need of commenting about what it is doing and why.
> 
> The changelog alone doesn't cut it.
Thanks, Dave, Will add some comments