RE: [PATCH 04/12] platform/x86: dell-smbios: Switch to a WMI-ACPI interface

[Mario.Limonciello]

> -----Original Message-----
> From: Pali RohÃr [mailto:pali.rohar@xxxxxxxxx]
> Sent: Monday, September 25, 2017 12:19 PM
> To: Limonciello, Mario <Mario_Limonciello@xxxxxxxx>
> Cc: dvhart@xxxxxxxxxxxxx; LKML <linux-kernel@xxxxxxxxxxxxxxx>; platform-driver-
> x86@xxxxxxxxxxxxxxx; quasisec@xxxxxxxxxx
> Subject: Re: [PATCH 04/12] platform/x86: dell-smbios: Switch to a WMI-ACPI
> interface
> 
> On Thursday 21 September 2017 08:57:09 Mario Limonciello wrote:
> > The driver currently uses an SMI interface which grants direct access
> > to physical memory to the platform via a pointer.
> >
> > Changing this to operate over WMI-ACPI will use an ACPI OperationRegion
> > for a buffer of data storage when platform calls are performed.
> >
> > This is a safer approach to use in kernel drivers as the platform will
> > only have access to that OperationRegion.
> 
> In my opinion direct access is safer then using ACPI wrapper for same
> functionality.

I'd like to hear how this is safer.

> 
> Anyway, this change would break support for laptops without ACPI-WMI
> functionality. IIRC I read in some Dell ACPI-WMI documentation that Dell
> SMM via ACPI-WMI is not supported on all machines (probably older
> machines) and it is needed to check some vendor bit in DMI data if Dell
> SMM ACPI-WMI is really supported.
> 
> In linux kernel we do not want to remove support for older machines,
> just because machines with new firmware can use also different new
> communication method/protocol.
> 

As mentioned on other email, I'll rework to support both methods and
prefer WMI method.

> > As a result, this change removes the dependency on this driver on the
> > dcdbas kernel module.
> >
> > Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxxx>
> > ---
> >  drivers/platform/x86/Kconfig       |  8 ++--
> >  drivers/platform/x86/dell-smbios.c | 76 ++++++++++++++++++++++++++------------
> >  drivers/platform/x86/dell-smbios.h | 11 +++---
> >  3 files changed, 63 insertions(+), 32 deletions(-)
> >
> > diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
> > index 9e52f05daa2e..81d61c0f4ef8 100644
> > --- a/drivers/platform/x86/Kconfig
> > +++ b/drivers/platform/x86/Kconfig
> > @@ -92,13 +92,13 @@ config ASUS_LAPTOP
> >  	  If you have an ACPI-compatible ASUS laptop, say Y or M here.
> >
> >  config DELL_SMBIOS
> > -	tristate
> > -	select DCDBAS
> > +	tristate "Dell WMI SMBIOS calling interface"
> > +	depends on ACPI_WMI
> >  	---help---
> >  	This module provides common functions for kernel modules using
> > -	Dell SMBIOS.
> > +	Dell SMBIOS over ACPI-WMI.
> >
> > -	If you have a Dell laptop, say Y or M here.
> > +	If you have a Dell computer, say Y or M here.
> >
> >  config DELL_LAPTOP
> >  	tristate "Dell Laptop Extras"
> > diff --git a/drivers/platform/x86/dell-smbios.c b/drivers/platform/x86/dell-
> smbios.c
> > index e9b1ca07c872..c06262a89169 100644
> > --- a/drivers/platform/x86/dell-smbios.c
> > +++ b/drivers/platform/x86/dell-smbios.c
> > @@ -4,6 +4,7 @@
> >   *  Copyright (c) Red Hat <mjg@xxxxxxxxxx>
> >   *  Copyright (c) 2014 Gabriele Mazzotta <gabriele.mzt@xxxxxxxxx>
> >   *  Copyright (c) 2014 Pali RohÃr <pali.rohar@xxxxxxxxx>
> > + *  Copyright (c) 2017 Dell Inc.
> >   *
> >   *  Based on documentation in the libsmbios package:
> >   *  Copyright (C) 2005-2014 Dell Inc.
> > @@ -18,13 +19,12 @@
> >  #include <linux/module.h>
> >  #include <linux/dmi.h>
> >  #include <linux/err.h>
> > -#include <linux/gfp.h>
> >  #include <linux/mutex.h>
> > -#include <linux/slab.h>
> > -#include <linux/io.h>
> > -#include "../../firmware/dcdbas.h"
> > +#include <linux/wmi.h>
> >  #include "dell-smbios.h"
> >
> > +#define DELL_WMI_SMBIOS_GUID "A80593CE-A997-11DA-B012-
> B622A1EF5492"
> > +
> >  struct calling_interface_structure {
> >  	struct dmi_header header;
> >  	u16 cmdIOAddress;
> > @@ -76,20 +76,39 @@ void dell_smbios_release_buffer(void)
> >  }
> >  EXPORT_SYMBOL_GPL(dell_smbios_release_buffer);
> >
> > -void dell_smbios_send_request(int class, int select)
> > +int run_wmi_smbios_call(struct calling_interface_buffer *buffer)
> >  {
> > -	struct smi_cmd command;
> > +	struct acpi_buffer output = {ACPI_ALLOCATE_BUFFER, NULL};
> > +	struct acpi_buffer input;
> > +	union acpi_object *obj;
> > +	acpi_status status;
> > +
> > +	input.length = sizeof(struct calling_interface_buffer);
> > +	input.pointer = buffer;
> > +
> > +	status = wmi_evaluate_method(DELL_WMI_SMBIOS_GUID,
> > +				     0, 1, &input, &output);
> > +	if (ACPI_FAILURE(status)) {
> > +		pr_err("%x/%x [%x,%x,%x,%x] call failed\n",
> > +			buffer->class, buffer->select, buffer->input[0],
> > +			buffer->input[1], buffer->input[2], buffer->input[3]);
> > +			return -EIO;
> > +	}
> > +	obj = (union acpi_object *)output.pointer;
> > +	if (obj->type != ACPI_TYPE_BUFFER) {
> > +		pr_err("invalid type : %d\n", obj->type);
> > +		return -EIO;
> > +	}
> > +	memcpy(buffer, obj->buffer.pointer, input.length);
> >
> > -	command.magic = SMI_CMD_MAGIC;
> > -	command.command_address = da_command_address;
> > -	command.command_code = da_command_code;
> > -	command.ebx = virt_to_phys(buffer);
> > -	command.ecx = 0x42534931;
> > +	return 0;
> > +}
> >
> > +void dell_smbios_send_request(int class, int select)
> > +{
> >  	buffer->class = class;
> >  	buffer->select = select;
> > -
> > -	dcdbas_smi_request(&command);
> > +	run_wmi_smbios_call(buffer);
> >  }
> >  EXPORT_SYMBOL_GPL(dell_smbios_send_request);
> >
> > @@ -170,7 +189,7 @@ static void __init find_tokens(const struct dmi_header
> *dm, void *dummy)
> >  	}
> >  }
> >
> > -static int __init dell_smbios_init(void)
> > +static int dell_smbios_probe(struct wmi_device *wdev)
> >  {
> >  	int ret;
> >
> > @@ -181,11 +200,7 @@ static int __init dell_smbios_init(void)
> >  		return -ENODEV;
> >  	}
> >
> > -	/*
> > -	 * Allocate buffer below 4GB for SMI data--only 32-bit physical addr
> > -	 * is passed to SMI handler.
> > -	 */
> > -	buffer = (void *)__get_free_page(GFP_KERNEL | GFP_DMA32);
> > +	buffer = (void *)__get_free_page(GFP_KERNEL);
> >  	if (!buffer) {
> >  		ret = -ENOMEM;
> >  		goto fail_buffer;
> > @@ -198,17 +213,32 @@ static int __init dell_smbios_init(void)
> >  	return ret;
> >  }
> >
> > -static void __exit dell_smbios_exit(void)
> > +static int dell_smbios_remove(struct wmi_device *wdev)
> >  {
> >  	kfree(da_tokens);
> >  	free_page((unsigned long)buffer);
> > +	return 0;
> >  }
> >
> > -subsys_initcall(dell_smbios_init);
> > -module_exit(dell_smbios_exit);
> > +static const struct wmi_device_id dell_smbios_id_table[] = {
> > +	{ .guid_string = DELL_WMI_SMBIOS_GUID },
> > +	{ },
> > +};
> > +
> > +static struct wmi_driver dell_smbios_driver = {
> > +	.driver = {
> > +		.name = "dell-smbios",
> > +	},
> > +	.probe = dell_smbios_probe,
> > +	.remove = dell_smbios_remove,
> > +	.id_table = dell_smbios_id_table,
> > +};
> > +module_wmi_driver(dell_smbios_driver);
> > +
> >
> >  MODULE_AUTHOR("Matthew Garrett <mjg@xxxxxxxxxx>");
> >  MODULE_AUTHOR("Gabriele Mazzotta <gabriele.mzt@xxxxxxxxx>");
> >  MODULE_AUTHOR("Pali RohÃr <pali.rohar@xxxxxxxxx>");
> > -MODULE_DESCRIPTION("Common functions for kernel modules using Dell
> SMBIOS");
> > +MODULE_AUTHOR("Mario Limonciello <mario.limonciello@xxxxxxxx>");
> > +MODULE_DESCRIPTION("Common functions for kernel modules using Dell
> SMBIOS over WMI");
> >  MODULE_LICENSE("GPL");
> > diff --git a/drivers/platform/x86/dell-smbios.h b/drivers/platform/x86/dell-
> smbios.h
> > index 45cbc2292cd3..e1e29697b362 100644
> > --- a/drivers/platform/x86/dell-smbios.h
> > +++ b/drivers/platform/x86/dell-smbios.h
> > @@ -4,6 +4,7 @@
> >   *  Copyright (c) Red Hat <mjg@xxxxxxxxxx>
> >   *  Copyright (c) 2014 Gabriele Mazzotta <gabriele.mzt@xxxxxxxxx>
> >   *  Copyright (c) 2014 Pali RohÃr <pali.rohar@xxxxxxxxx>
> > + *  Copyright (c) 2017 Dell Inc.
> >   *
> >   *  Based on documentation in the libsmbios package:
> >   *  Copyright (C) 2005-2014 Dell Inc.
> > @@ -18,14 +19,14 @@
> >
> >  struct notifier_block;
> >
> > -/* This structure will be modified by the firmware when we enter
> > - * system management mode, hence the volatiles */
> > -
> >  struct calling_interface_buffer {
> >  	u16 class;
> >  	u16 select;
> > -	volatile u32 input[4];
> > -	volatile u32 output[4];
> > +	u32 input[4];
> > +	u32 output[4];
> > +	u32 argattrib;
> > +	u32 blength;
> > +	u8 data[4052];
> >  } __packed;
> >
> >  struct calling_interface_token {
> 
> --
> Pali RohÃr
> pali.rohar@xxxxxxxxx