linux-kernel - Re: [PATCH v3 15/15] Drivers: hv: Add modules to expose /dev/mshv to VMMs running on Hyper-V

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Message-ID: <ZQ3y47GDfhjf23Rh@liuwe-devbox-debian-v2>
Date:   Fri, 22 Sep 2023 20:02:43 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Nuno Das Neves <nunodasneves@...ux.microsoft.com>
Cc:     linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linux-arch@...r.kernel.org, patches@...ts.linux.dev,
        mikelley@...rosoft.com, kys@...rosoft.com, wei.liu@...nel.org,
        gregkh@...uxfoundation.org, haiyangz@...rosoft.com,
        decui@...rosoft.com, apais@...ux.microsoft.com,
        Tianyu.Lan@...rosoft.com, ssengar@...ux.microsoft.com,
        mukeshrathor@...rosoft.com, stanislav.kinsburskiy@...il.com,
        jinankjain@...ux.microsoft.com, vkuznets@...hat.com,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com, will@...nel.org,
        catalin.marinas@....com
Subject: Re: [PATCH v3 15/15] Drivers: hv: Add modules to expose /dev/mshv to
 VMMs running on Hyper-V

On Fri, Sep 22, 2023 at 11:38:35AM -0700, Nuno Das Neves wrote:
> Add mshv, mshv_root, and mshv_vtl modules:
> 
> Module mshv is the parent module to the other two. It provides /dev/mshv,
> plus some common hypercall helper code. When one of the child modules is
> loaded, it is registered with the mshv module, which then provides entry
> point(s) to the child module via the IOCTLs defined in uapi/linux/mshv.h.
> 
> E.g. When the mshv_root module is loaded, it registers itself, and the
> MSHV_CREATE_PARTITION IOCTL becomes available in /dev/mshv. That is used to
> get a partition fd managed by mshv_root.
> 
> Similarly for mshv_vtl module, there is MSHV_CREATE_VTL, which creates
> an fd representing the lower vtl, managed by mshv_vtl.
> 
> Module mshv_root provides APIs for creating and managing child partitions.
> It defines abstractions for partitions (vms), vps (vcpus), and other things
> related to running a guest. It exposes the userspace interfaces for a VMM
> to manage the guest.
> 
> Module mshv_vtl provides VTL (Virtual Trust Level) support for VMMs. In
> this scenario, the host kernel and VMM run in a higher trust level than the
> guest, but within the same partition. This provides better isolation and
> performance.
> 
> Signed-off-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>

As far as I can tell, all my comments from the previous version are
addressed. I believe Saurabh and Boqun's comments are addressed, too.

The code looks good to me, so:

Acked-by: Wei Liu <wei.liu@...nel.org>

I will wait for some time for others to chime in, just in case the
community has more comments.