linux-kernel - Re: [PATCH v16.1 6/9] virtio-balloon: Add support for providing free page reports to host

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Message-Id: <B3E5574A-B696-4239-8F1D-ED51496DD59C@redhat.com>
Date:   Tue, 11 Feb 2020 18:04:28 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Alexander Duyck <alexander.h.duyck@...ux.intel.com>
Cc:     David Hildenbrand <david@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        willy@...radead.org, mhocko@...nel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, mgorman@...hsingularity.net,
        vbabka@...e.cz, yang.zhang.wz@...il.com, nitesh@...hat.com,
        konrad.wilk@...cle.com, pagupta@...hat.com, riel@...riel.com,
        lcapitulino@...hat.com, dave.hansen@...el.com,
        wei.w.wang@...el.com, aarcange@...hat.com, pbonzini@...hat.com,
        dan.j.williams@...el.com, osalvador@...e.de
Subject: Re: [PATCH v16.1 6/9] virtio-balloon: Add support for providing free page reports to host



> Am 11.02.2020 um 17:33 schrieb Alexander Duyck <alexander.h.duyck@...ux.intel.com>:
> 
> On Tue, 2020-02-11 at 16:13 +0100, David Hildenbrand wrote:
>>>> AFAIKs, the guest could inflate/deflate (esp. temporarily) and
>>>> communicate via "actual" the actual balloon size as he sees it.
>>> 
>>> OK so you want hinted but unused pages counted, and reported
>>> in "actual"? That's a vmexit before each page use ...
>> 
>> No, not at all. I rather meant, that it is unclear how
>> inflation/deflation requests and "actual" *could* interact. Especially
>> if we would consider free page reporting as some way of inflation
>> (+immediate deflation) triggered by the guest. IMHO, we would not touch
>> "actual" in that case.
>> 
>> But as I said, I am totally fine with keeping it as is in this patch.
>> IOW not glue free page reporting to inflation/deflation but let it act
>> like something different with its own semantics (and document these
>> properly).
>> 
> 
> Okay, so before I post v17 am I leaving the virtio-balloon changes as they
> were then?

I‘d say yes :)