linux-kernel - Re: [PATCH v2 03/17] Drivers: hv: vmbus: skip VMBus initialization if Linux is root

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Date:   Thu, 12 Nov 2020 16:24:38 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Wei Liu <wei.liu@...nel.org>,
        Linux on Hyper-V List <linux-hyperv@...r.kernel.org>
Cc:     virtualization@...ts.linux-foundation.org,
        Linux Kernel List <linux-kernel@...r.kernel.org>,
        Michael Kelley <mikelley@...rosoft.com>,
        Vineeth Pillai <viremana@...ux.microsoft.com>,
        Sunil Muthuswamy <sunilmut@...rosoft.com>,
        Nuno Das Neves <nunodasneves@...ux.microsoft.com>,
        Wei Liu <wei.liu@...nel.org>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>
Subject: Re: [PATCH v2 03/17] Drivers: hv: vmbus: skip VMBus initialization
 if Linux is root

Wei Liu <wei.liu@...nel.org> writes:

> There is no VMBus and the other infrastructures initialized in
> hv_acpi_init when Linux is running as the root partition.
>
> Signed-off-by: Wei Liu <wei.liu@...nel.org>
> ---
>  drivers/hv/vmbus_drv.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 4fad3e6745e5..37c4d3a28309 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -2612,6 +2612,9 @@ static int __init hv_acpi_init(void)
>  	if (!hv_is_hyperv_initialized())
>  		return -ENODEV;
>  
> +	if (hv_root_partition)
> +		return -ENODEV;
> +

Nit: any particular reason why we need to return an error from here? I'd
suggest we 'return 0;' if it doesn't break anything (we're still running
on Hyper-V, it's just a coincedence that there's nothing to do here,
eventually we may get some devices/handlers I guess. Also, there's going
to be server-side Vmbus eventually, we may as well initialize it here.

>  	init_completion(&probe_event);
>  
>  	/*

-- 
Vitaly