Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH v4 2/2] kvm: Use huge pages for DAX-backed files
To:     Dan Williams <dan.j.williams@intel.com>
Cc:     Sean Christopherson <sean.j.christopherson@intel.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        David Hildenbrand <david@redhat.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Alexander Duyck <alexander.h.duyck@linux.intel.com>,
        linux-nvdimm <linux-nvdimm@lists.01.org>,
        X86 ML <x86@kernel.org>, KVM list <kvm@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "Zeng, Jason" <jason.zeng@intel.com>
References: <20191211213207.215936-1-brho@google.com>
 <20191211213207.215936-3-brho@google.com>
 <20191212173413.GC3163@linux.intel.com>
 <CAPcyv4hkz8XCETELBaUOjHQf3=VyVB=KWeRVEPYejvdsg3_MWA@mail.gmail.com>
From:   Barret Rhoden <brho@google.com>
Message-ID: <b50720a2-5358-19ea-a45e-a0c0628c68b0@google.com>
Date:   Thu, 12 Dec 2019 14:16:33 -0500
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.9.0
MIME-Version: 1.0
In-Reply-To: <CAPcyv4hkz8XCETELBaUOjHQf3=VyVB=KWeRVEPYejvdsg3_MWA@mail.gmail.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 12/12/19 12:37 PM, Dan Williams wrote:
> Yeah, since device-dax is the only path to support longterm page
> pinning for vfio device assignment, testing with device-dax + 1GB
> pages would be a useful sanity check.

What are the issues with fs-dax and page pinning?  Is that limitation 
something that is permanent and unfixable (by me or anyone)?

I'd like to put a lot more in a DAX/pmem region than just a guest's 
memory, and having a mountable filesystem would be extremely convenient.

Thanks,

Barret