linux-kernel - RE: [PATCH 6/7] Drivers: hv: vmbus: Suspend/resume the vmbus itself for hibernation

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Message-ID: <MWHPR21MB078461F2DB6FE0A6D0647B70D7DC0@MWHPR21MB0784.namprd21.prod.outlook.com>
Date:   Tue, 30 Jul 2019 23:25:37 +0000
From:   Michael Kelley <mikelley@...rosoft.com>
To:     Dexuan Cui <decui@...rosoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>,
        "sashal@...nel.org" <sashal@...nel.org>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 6/7] Drivers: hv: vmbus: Suspend/resume the vmbus itself
 for hibernation

From: Dexuan Cui <decui@...rosoft.com>  Sent: Monday, July 8, 2019 10:30 PM
> 
> This is needed when we resume the old kernel from the "current" kernel.

Perhaps a bit more descriptive commit message could be supplied?

> 
> Signed-off-by: Dexuan Cui <decui@...rosoft.com>
> ---
>  drivers/hv/connection.c   |  3 +--
>  drivers/hv/hyperv_vmbus.h |  2 ++
>  drivers/hv/vmbus_drv.c    | 40 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 43 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
> index 09829e1..806319c 100644
> --- a/drivers/hv/connection.c
> +++ b/drivers/hv/connection.c
> @@ -59,8 +59,7 @@ static __u32 vmbus_get_next_version(__u32 current_version)
>  	}
>  }
> 
> -static int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo,
> -					__u32 version)
> +int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo, u32 version)
>  {
>  	int ret = 0;
>  	unsigned int cur_cpu;
> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
> index 26ea161..e657197 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -274,6 +274,8 @@ struct vmbus_msginfo {
> 
>  extern struct vmbus_connection vmbus_connection;
> 
> +int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo, u32 version);
> +
>  static inline void vmbus_send_interrupt(u32 relid)
>  {
>  	sync_set_bit(relid, vmbus_connection.send_int_page);
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 1c2d935..1730e7b 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -2045,6 +2045,41 @@ static int vmbus_acpi_add(struct acpi_device *device)
>  	return ret_val;
>  }
> 
> +static int vmbus_bus_suspend(struct device *dev)
> +{
> +	vmbus_initiate_unload(false);
> +
> +	vmbus_connection.conn_state = DISCONNECTED;
> +
> +	return 0;
> +}
> +
> +static int vmbus_bus_resume(struct device *dev)
> +{
> +	struct vmbus_channel_msginfo *msginfo;
> +	size_t msgsize;
> +	int ret;
> +
> +	msgsize = sizeof(*msginfo) +
> +		  sizeof(struct vmbus_channel_initiate_contact);
> +
> +	msginfo = kzalloc(msgsize, GFP_KERNEL);
> +
> +	if (msginfo == NULL)
> +		return -ENOMEM;
> +
> +	ret = vmbus_negotiate_version(msginfo, vmbus_proto_version);

I think this code answers my earlier question:  Upon resume, we negotiate the same
VMbus protocol version we had at time of hibernation, even if running on a newer
version of Hyper-V that might support newer protocol versions.  Hence the offer
messages should not have any previously reserved fields now being used.   A
comment to this effect would be useful.

> +
> +	kfree(msginfo);
> +
> +	if (ret != 0)
> +		return ret;
> +
> +	vmbus_request_offers();
> +
> +	return 0;
> +}
> +
>  static const struct acpi_device_id vmbus_acpi_device_ids[] = {
>  	{"VMBUS", 0},
>  	{"VMBus", 0},
> @@ -2052,6 +2087,10 @@ static int vmbus_acpi_add(struct acpi_device *device)
>  };
>  MODULE_DEVICE_TABLE(acpi, vmbus_acpi_device_ids);
> 
> +static const struct dev_pm_ops vmbus_bus_pm = {
> +	SET_SYSTEM_SLEEP_PM_OPS(vmbus_bus_suspend, vmbus_bus_resume)
> +};
> +
>  static struct acpi_driver vmbus_acpi_driver = {
>  	.name = "vmbus",
>  	.ids = vmbus_acpi_device_ids,
> @@ -2059,6 +2098,7 @@ static int vmbus_acpi_add(struct acpi_device *device)
>  		.add = vmbus_acpi_add,
>  		.remove = vmbus_acpi_remove,
>  	},
> +	.drv.pm = &vmbus_bus_pm,
>  };
> 
>  static void hv_kexec_handler(void)
> --
> 1.8.3.1