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Message-ID: <c39553770dc895d7a4f172c337f3bad77642f131.camel@infradead.org>
Subject: Re: [PATCH v3 00/17] Introducing Linux root partition support for
 Microsoft Hypervisor
From:   David Woodhouse <dwmw2@infradead.org>
To:     Wei Liu <wei.liu@kernel.org>,
        "Enrico Weigelt, metux IT consult" <lkml@metux.net>,
        kvm <kvm@vger.kernel.org>
Cc:     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
Date:   Tue, 02 Feb 2021 10:40:43 +0000
In-Reply-To: <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>
         <20201215164245.yrorpipw2476w35e@liuwe-devbox-debian-v2>
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On Tue, 2020-12-15 at 16:42 +0000, Wei Liu wrote:
> On Tue, Dec 15, 2020 at 04:25:03PM +0100, Enrico Weigelt, metux IT consul=
t wrote:
> > On 03.12.20 00:22, Wei Liu wrote:
> >=20
> > Hi,
> >=20
> > > 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.
> >=20
> > My idea was using the same uapi for both hypervisors, so that we can us=
e
> > the same userlands for both.
> >=20
> > Are the semantis so different that we can't provide the same API ?
>=20
> 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.

I'm not sure I understand.

KVM is the Linux userspace API for virtualisation. It is designed to be
versatile enough that it can support multiple implementations across
multiple architectures, including both AMD SVM and Intel VMX on x86.

Are you saying that KVM has *failed* to be versatile enough that this
can be "just another implementation"? What are the problems? Is it
unfixable?=20

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