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

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Message-ID: <4192066a-79f3-2b3e-386f-c4ec9b6dd8fd@intel.com>
Date:   Thu, 30 Aug 2018 12:07:11 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Zhang Yi <yi.z.zhang@...ux.intel.com>, 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 V4 4/4] kvm: add a check if pfn is from NVDIMM pmem.

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.