Subject: Re: [PATCH] add POWER Virtual Management Channel driver

From: Greg Kroah-Hartman <[email-masked]>
Date: Tue, 16 Feb 2016 14:18:22 -0800

On Tue, Feb 16, 2016 at 02:43:13PM -0600, Steven Royer wrote:
> From: Steven Royer <[email-masked]>
> 
> The ibmvmc driver is a device driver for the POWER Virtual Management
> Channel virtual adapter on the PowerVM platform.  It is used to
> communicate with the hypervisor for virtualization management.  It
> provides both request/response and asynchronous message support through
> the /dev/ibmvmc node.

What is the protocol for that device node?

Where is the documentation here?  Why does this have to be a character
device?  Why can't it fit in with other drivers of this type?

> 
> Signed-off-by: Steven Royer <[email-masked]>
> ---
> This is used by the PowerVM NovaLink project.  You can see development history on github:
> https://github.com/powervm/ibmvmc
> 
>  Documentation/ioctl/ioctl-number.txt |    1 +
>  MAINTAINERS                          |    5 +
>  arch/powerpc/include/asm/hvcall.h    |    3 +-
>  drivers/misc/Kconfig                 |    9 +
>  drivers/misc/Makefile                |    1 +
>  drivers/misc/ibmvmc.c                | 1882 ++++++++++++++++++++++++++++++++++
>  drivers/misc/ibmvmc.h                |  203 ++++
>  7 files changed, 2103 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/misc/ibmvmc.c
>  create mode 100644 drivers/misc/ibmvmc.h
> 
> diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt
> index 91261a3..d5f5f4f 100644
> --- a/Documentation/ioctl/ioctl-number.txt
> +++ b/Documentation/ioctl/ioctl-number.txt
> @@ -324,6 +324,7 @@ Code  Seq#(hex)	Include File		Comments
>  0xCA	80-8F	uapi/scsi/cxlflash_ioctl.h
>  0xCB	00-1F	CBM serial IEC bus	in development:
>  					<mailto:[email-masked]>
> +0xCC	00-0F	drivers/misc/ibmvmc.h	pseries VMC driver
>  0xCD	01	linux/reiserfs_fs.h
>  0xCF	02	fs/cifs/ioctl.c
>  0xDB	00-0F	drivers/char/mwave/mwavepub.h
> diff --git a/MAINTAINERS b/MAINTAINERS
> index cc2f753..c39dca2 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -5353,6 +5353,11 @@ L:	[email-masked]
>  S:	Supported
>  F:	drivers/net/ethernet/ibm/ibmvnic.*
>  
> +IBM Power Virtual Management Channel Driver
> +M:	Steven Royer <[email-masked]>
> +S:	Supported
> +F:	drivers/misc/ibmvmc.*
> +
>  IBM Power Virtual SCSI Device Drivers
>  M:	Tyrel Datwyler <[email-masked]>
>  L:	[email-masked]
> diff --git a/arch/powerpc/include/asm/hvcall.h b/arch/powerpc/include/asm/hvcall.h
> index e3b54dd..1ee6f2b 100644
> --- a/arch/powerpc/include/asm/hvcall.h
> +++ b/arch/powerpc/include/asm/hvcall.h
> @@ -274,7 +274,8 @@
>  #define H_COP			0x304
>  #define H_GET_MPP_X		0x314
>  #define H_SET_MODE		0x31C
> -#define MAX_HCALL_OPCODE	H_SET_MODE
> +#define H_REQUEST_VMC		0x360
> +#define MAX_HCALL_OPCODE	H_REQUEST_VMC
>  
>  /* H_VIOCTL functions */
>  #define H_GET_VIOA_DUMP_SIZE	0x01
> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> index 054fc10..f8d9113 100644
> --- a/drivers/misc/Kconfig
> +++ b/drivers/misc/Kconfig
> @@ -526,6 +526,15 @@ config VEXPRESS_SYSCFG
>  	  bus. System Configuration interface is one of the possible means
>  	  of generating transactions on this bus.
>  
> +config IBMVMC
> +	tristate "IBM Virtual Management Channel support"
> +	depends on PPC_PSERIES
> +	help
> +	  This is the IBM POWER Virtual Management Channel
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called ibmvmc.
> +
>  source "drivers/misc/c2port/Kconfig"
>  source "drivers/misc/eeprom/Kconfig"
>  source "drivers/misc/cb710/Kconfig"
> diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
> index 537d7f3..08336b3 100644
> --- a/drivers/misc/Makefile
> +++ b/drivers/misc/Makefile
> @@ -56,3 +56,4 @@ obj-$(CONFIG_GENWQE)		+= genwqe/
>  obj-$(CONFIG_ECHO)		+= echo/
>  obj-$(CONFIG_VEXPRESS_SYSCFG)	+= vexpress-syscfg.o
>  obj-$(CONFIG_CXL_BASE)		+= cxl/
> +obj-$(CONFIG_IBMVMC)		+= ibmvmc.o
> diff --git a/drivers/misc/ibmvmc.c b/drivers/misc/ibmvmc.c
> new file mode 100644
> index 0000000..fb943b7
> --- /dev/null
> +++ b/drivers/misc/ibmvmc.c
> @@ -0,0 +1,1882 @@
> +/*
> + * IBM Power Systems Virtual Management Channel Support.
> + *
> + * Copyright (c) 2004, 2016 IBM Corp.
> + *   Dave Engebretsen [email-masked]
> + *   Steven Royer [email-masked]
> + *   Adam Reznechek [email-masked]
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version 2
> + * of the License, or (at your option) any later version.

I have to ask, but do you really mean "or any later version"?

> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/major.h>
> +#include <linux/string.h>
> +#include <linux/fcntl.h>
> +#include <linux/slab.h>
> +#include <linux/poll.h>
> +#include <linux/init.h>
> +#include <linux/fs.h>
> +#include <linux/interrupt.h>
> +#include <linux/spinlock.h>
> +#include <linux/percpu.h>
> +#include <linux/delay.h>
> +#include <linux/uaccess.h>
> +#include <linux/io.h>
> +#include <linux/device.h>
> +
> +#include <asm/byteorder.h>
> +#include <asm/irq.h>
> +#include <asm/vio.h>

Why are these asm files needed?

> +
> +#include "ibmvmc.h"

Why do you have a .h file for a single-file driver?  That shouldn't be
needed at all, unless you have an odd user api, and if so, it better be
documented...

> +
> +#define IBMVMC_DRIVER_VERSION "1.0"
> +
> +MODULE_DESCRIPTION("IBM VMC");
> +MODULE_AUTHOR("Steven Royer <[email-masked]>");
> +MODULE_LICENSE("GPL");
> +MODULE_VERSION(IBMVMC_DRIVER_VERSION);
> +
> +
> +/*
> + * Static global variables
> + */
> +static DECLARE_WAIT_QUEUE_HEAD(ibmvmc_read_wait);
> +
> +static const char ibmvmc_driver_name[] = "ibmvmc";
> +static const char ibmvmc_workq_name[] = "ibmvmc";
> +
> +static struct ibmvmc_struct ibmvmc;
> +static struct ibmvmc_hmc hmcs[MAX_HMCS];
> +static struct crq_server_adapter ibmvmc_adapter;
> +static dev_t ibmvmc_chrdev;
> +
> +static int ibmvmc_max_buf_pool_size = DEFAULT_BUF_POOL_SIZE;
> +static int ibmvmc_max_hmcs = DEFAULT_HMCS;
> +static int ibmvmc_max_mtu = DEFAULT_MTU;
> +static struct class *ibmvmc_class;
> +struct device *ibmvmc_dev;

Those are huge flags to me, why would you ever have a static pointer to
a device?  You should never deal with a "raw" struct device, unless
something is really odd...

> +
> +/* Module parameters */
> +module_param_named(buf_pool_size, ibmvmc_max_buf_pool_size,
> +		   int, S_IRUGO | S_IWUSR);
> +MODULE_PARM_DESC(buf_pool_size, "Buffer pool size");
> +module_param_named(max_hmcs, ibmvmc_max_hmcs, int, S_IRUGO | S_IWUSR);
> +MODULE_PARM_DESC(max_hmcs, "Max HMCs");
> +module_param_named(max_mtu, ibmvmc_max_mtu, int, S_IRUGO | S_IWUSR);
> +MODULE_PARM_DESC(max_mtu, "Max MTU");
> +
> +
> +static inline long h_copy_rdma(s64 length, u64 sliobn, u64 slioba,
> +	u64 dliobn, u64 dlioba)
> +{
> +	long rc = 0;
> +
> +	/* Ensure all writes to source memory are visible before hcall */
> +	mb();
> +	pr_debug("ibmvmc: h_copy_rdma(0x%llx, 0x%llx, 0x%llx, 0x%llx, 0x%llx\n",
> +			length, sliobn, slioba, dliobn, dlioba);

It's a driver, use dev_dbg() please.

> +	rc = plpar_hcall_norets(H_COPY_RDMA, length, sliobn, slioba,
> +			dliobn, dlioba);
> +	pr_debug("ibmvmc: h_copy_rdma rc = 0x%lx\n", rc);
> +
> +	return rc;
> +}
> +
> +static inline void h_free_crq(uint32_t unit_address)
> +{
> +	long rc = 0;
> +
> +	do {
> +		if (H_IS_LONG_BUSY(rc))
> +			msleep(get_longbusy_msecs(rc));
> +
> +		rc = plpar_hcall_norets(H_FREE_CRQ, unit_address);
> +	} while ((rc == H_BUSY) || (H_IS_LONG_BUSY(rc)));

endless loop?  Not good.

> +}
> +
> +/**
> + * h_request_vmc: - request a hypervisor virtual management channel device
> + * @vmc_index: drc index of the vmc device created
> + *
> + * Requests the hypervisor create a new virtual management channel device,
> + * allowing this partition to send hypervisor virtualization control commands.
> + *
> + */
> +static inline long h_request_vmc(u32 *vmc_index)
> +{
> +	long rc = 0;
> +	unsigned long retbuf[PLPAR_HCALL_BUFSIZE];
> +
> +	do {
> +		if (H_IS_LONG_BUSY(rc))
> +			msleep(get_longbusy_msecs(rc));
> +
> +		/* Call to request the VMC device from phyp */
> +		rc = plpar_hcall(H_REQUEST_VMC, retbuf);
> +		pr_debug("ibmvmc: h_request_vmc rc = 0x%lx\n", rc);
> +		*vmc_index = retbuf[0];
> +	} while ((rc == H_BUSY) || (H_IS_LONG_BUSY(rc)));

Another endless loop?  Your hardware must never fail :)

> +
> +	return rc;
> +}
> +
> +/* routines for managing a command/response queue */
> +/**
> + * ibmvmc_handle_event: - Interrupt handler for crq events
> + * @irq:        number of irq to handle, not used
> + * @dev_instance: crq_server_adapter that received interrupt
> + *
> + * Disables interrupts and schedules ibmvmc_task
> + * Always returns IRQ_HANDLED
> + */
> +static irqreturn_t ibmvmc_handle_event(int irq, void *dev_instance)
> +{
> +	struct crq_server_adapter *adapter =
> +		(struct crq_server_adapter *)dev_instance;
> +
> +	vio_disable_interrupts(to_vio_dev(adapter->dev));
> +	queue_work(adapter->work_queue, &adapter->work);
> +
> +	return IRQ_HANDLED;

No shared interrupt handling?

> +}
> +
> +	/* Dynamically allocate ibmvmc major number */
> +	if (alloc_chrdev_region(&ibmvmc_chrdev, 0, VMC_NUM_MINORS,
> +		ibmvmc_driver_name)) {
> +		pr_err("ibmvmc: unable to allocate a dev_t\n");
> +		rc = -EIO;
> +		goto alloc_chrdev_failed;
> +	}

A whole major number for one minor?  Use the misc class instead please.

And finally, you only have a self-sign-off here, which is fine for
trivial stuff, but I want to see that other people actually believe this
code is correct and they agree with it.  Get others to review it first
before making the community (i.e. me) do their work for them.  IBM has a
whole bunch of people that do this as part of their job, don't ignore
them...

bah.

greg k-h