Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Tue, 15 Dec 2020 16:42:45 +0000
From:   Wei Liu <wei.liu@kernel.org>
To:     "Enrico Weigelt, metux IT consult" <lkml@metux.net>
Cc:     Wei Liu <wei.liu@kernel.org>,
        Linux on Hyper-V List <linux-hyperv@vger.kernel.org>,
        virtualization@lists.linux-foundation.org,
        Linux Kernel List <linux-kernel@vger.kernel.org>,
        Michael Kelley <mikelley@microsoft.com>,
        Vineeth Pillai <viremana@linux.microsoft.com>,
        Sunil Muthuswamy <sunilmut@microsoft.com>,
        Nuno Das Neves <nunodasneves@linux.microsoft.com>,
        sameo@linux.intel.com, robert.bradford@intel.com,
        sebastien.boeuf@intel.com
Subject: Re: [PATCH v3 00/17] Introducing Linux root partition support for
 Microsoft Hypervisor
Message-ID: <20201215164245.yrorpipw2476w35e@liuwe-devbox-debian-v2>
References: <20201124170744.112180-1-wei.liu@kernel.org>
 <227127cf-bfea-4a06-fcbc-f6c46102e9e6@metux.net>
 <20201202232234.5buzu5wysiaro3hc@liuwe-devbox-debian-v2>
 <87d94c39-e801-fbc6-8f7f-1f1b00fa719d@metux.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <87d94c39-e801-fbc6-8f7f-1f1b00fa719d@metux.net>
User-Agent: NeoMutt/20180716
Precedence: bulk

On Tue, Dec 15, 2020 at 04:25:03PM +0100, Enrico Weigelt, metux IT consult wrote:
> On 03.12.20 00:22, Wei Liu wrote:
> 
> Hi,
> 
> > I don't follow. Do you mean reusing /dev/kvm but with a different set of
> > APIs underneath? I don't think that will work.
> 
> My idea was using the same uapi for both hypervisors, so that we can use
> the same userlands for both.
> 
> Are the semantis so different that we can't provide the same API ?

We can provide some similar APIs for ease of porting, but can't provide
1:1 mappings. By definition KVM and MSHV are two different things. There
is no goal to make one ABI / API compatible with the other.

> 
> > In any case, the first version of /dev/mshv was posted a few days ago
> > [0].  While we've chosen to follow closely KVM's model, Microsoft
> > Hypervisor has its own APIs.
> 
> I have to admit, I don't know much about hyperv - what are the main
> differences (from userland perspective) between hyperv and kvm ?
> 

They have different architecture and hence different ways to deal with
things. The difference will inevitably make its way to userland.

Without going into all the details, you can have a look how Xen and KVM
differ architecturally. That will give you a pretty good idea on the
differences.

Wei.

> 
> --mtx
> 
> -- 
> ---
> Hinweis: unverschl?sselte E-Mails k?nnen leicht abgeh?rt und manipuliert
> werden ! F?r eine vertrauliche Kommunikation senden Sie bitte ihren
> GPG/PGP-Schl?ssel zu.
> ---
> Enrico Weigelt, metux IT consult
> Free software and Linux embedded engineering
> info@metux.net -- +49-151-27565287