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Date: Thu, 18 Aug 2016 09:29:37 -0700
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: lkml <linux-kernel@...r.kernel.org>,
"3.8+" <stable@...r.kernel.org>, Mark Laws <mdl@...z.org>
Subject: Re: [PATCH 4.7 172/186] Input: i8042 - break load dependency between
atkbd/psmouse and i8042
On Thu, Aug 18, 2016 at 6:59 AM, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
> 4.7-stable review patch. If anyone has any objections, please let me know.
Greg, please hold this patch off till your next cycle. I will be
sending a fixup for it to Linus today or tomorrow.
Thanks!
>
> ------------------
>
> From: Dmitry Torokhov <dmitry.torokhov@...il.com>
>
> commit 4097461897df91041382ff6fcd2bfa7ee6b2448c upstream.
>
> As explained in 1407814240-4275-1-git-send-email-decui@...rosoft.com we
> have a hard load dependency between i8042 and atkbd which prevents
> keyboard from working on Gen2 Hyper-V VMs.
>
>> hyperv_keyboard invokes serio_interrupt(), which needs a valid serio
>> driver like atkbd.c. atkbd.c depends on libps2.c because it invokes
>> ps2_command(). libps2.c depends on i8042.c because it invokes
>> i8042_check_port_owner(). As a result, hyperv_keyboard actually
>> depends on i8042.c.
>>
>> For a Generation 2 Hyper-V VM (meaning no i8042 device emulated), if a
>> Linux VM (like Arch Linux) happens to configure CONFIG_SERIO_I8042=m
>> rather than =y, atkbd.ko can't load because i8042.ko can't load(due to
>> no i8042 device emulated) and finally hyperv_keyboard can't work and
>> the user can't input: https://bugs.archlinux.org/task/39820
>> (Ubuntu/RHEL/SUSE aren't affected since they use CONFIG_SERIO_I8042=y)
>
> To break the dependency we move away from using i8042_check_port_owner()
> and instead allow serio port owner specify a mutex that clients should use
> to serialize PS/2 command stream.
>
> Reported-by: Mark Laws <mdl@...z.org>
> Tested-by: Mark Laws <mdl@...z.org>
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>
> ---
> drivers/input/serio/i8042.c | 16 +---------------
> drivers/input/serio/libps2.c | 10 ++++------
> include/linux/i8042.h | 6 ------
> include/linux/serio.h | 24 +++++++++++++++++++-----
> 4 files changed, 24 insertions(+), 32 deletions(-)
>
> --- a/drivers/input/serio/i8042.c
> +++ b/drivers/input/serio/i8042.c
> @@ -1277,6 +1277,7 @@ static int __init i8042_create_kbd_port(
> serio->start = i8042_start;
> serio->stop = i8042_stop;
> serio->close = i8042_port_close;
> + serio->ps2_cmd_mutex = &i8042_mutex;
> serio->port_data = port;
> serio->dev.parent = &i8042_platform_device->dev;
> strlcpy(serio->name, "i8042 KBD port", sizeof(serio->name));
> @@ -1373,21 +1374,6 @@ static void i8042_unregister_ports(void)
> }
> }
>
> -/*
> - * Checks whether port belongs to i8042 controller.
> - */
> -bool i8042_check_port_owner(const struct serio *port)
> -{
> - int i;
> -
> - for (i = 0; i < I8042_NUM_PORTS; i++)
> - if (i8042_ports[i].serio == port)
> - return true;
> -
> - return false;
> -}
> -EXPORT_SYMBOL(i8042_check_port_owner);
> -
> static void i8042_free_irqs(void)
> {
> if (i8042_aux_irq_registered)
> --- a/drivers/input/serio/libps2.c
> +++ b/drivers/input/serio/libps2.c
> @@ -56,19 +56,17 @@ EXPORT_SYMBOL(ps2_sendbyte);
>
> void ps2_begin_command(struct ps2dev *ps2dev)
> {
> - mutex_lock(&ps2dev->cmd_mutex);
> + struct mutex *m = ps2dev->serio->ps2_cmd_mutex ?: &ps2dev->cmd_mutex;
>
> - if (i8042_check_port_owner(ps2dev->serio))
> - i8042_lock_chip();
> + mutex_lock(m);
> }
> EXPORT_SYMBOL(ps2_begin_command);
>
> void ps2_end_command(struct ps2dev *ps2dev)
> {
> - if (i8042_check_port_owner(ps2dev->serio))
> - i8042_unlock_chip();
> + struct mutex *m = ps2dev->serio->ps2_cmd_mutex ?: &ps2dev->cmd_mutex;
>
> - mutex_unlock(&ps2dev->cmd_mutex);
> + mutex_unlock(m);
> }
> EXPORT_SYMBOL(ps2_end_command);
>
> --- a/include/linux/i8042.h
> +++ b/include/linux/i8042.h
> @@ -62,7 +62,6 @@ struct serio;
> void i8042_lock_chip(void);
> void i8042_unlock_chip(void);
> int i8042_command(unsigned char *param, int command);
> -bool i8042_check_port_owner(const struct serio *);
> int i8042_install_filter(bool (*filter)(unsigned char data, unsigned char str,
> struct serio *serio));
> int i8042_remove_filter(bool (*filter)(unsigned char data, unsigned char str,
> @@ -83,11 +82,6 @@ static inline int i8042_command(unsigned
> return -ENODEV;
> }
>
> -static inline bool i8042_check_port_owner(const struct serio *serio)
> -{
> - return false;
> -}
> -
> static inline int i8042_install_filter(bool (*filter)(unsigned char data, unsigned char str,
> struct serio *serio))
> {
> --- a/include/linux/serio.h
> +++ b/include/linux/serio.h
> @@ -31,7 +31,8 @@ struct serio {
>
> struct serio_device_id id;
>
> - spinlock_t lock; /* protects critical sections from port's interrupt handler */
> + /* Protects critical sections from port's interrupt handler */
> + spinlock_t lock;
>
> int (*write)(struct serio *, unsigned char);
> int (*open)(struct serio *);
> @@ -40,16 +41,29 @@ struct serio {
> void (*stop)(struct serio *);
>
> struct serio *parent;
> - struct list_head child_node; /* Entry in parent->children list */
> + /* Entry in parent->children list */
> + struct list_head child_node;
> struct list_head children;
> - unsigned int depth; /* level of nesting in serio hierarchy */
> + /* Level of nesting in serio hierarchy */
> + unsigned int depth;
>
> - struct serio_driver *drv; /* accessed from interrupt, must be protected by serio->lock and serio->sem */
> - struct mutex drv_mutex; /* protects serio->drv so attributes can pin driver */
> + /*
> + * serio->drv is accessed from interrupt handlers; when modifying
> + * caller should acquire serio->drv_mutex and serio->lock.
> + */
> + struct serio_driver *drv;
> + /* Protects serio->drv so attributes can pin current driver */
> + struct mutex drv_mutex;
>
> struct device dev;
>
> struct list_head node;
> +
> + /*
> + * For use by PS/2 layer when several ports share hardware and
> + * may get indigestion when exposed to concurrent access (i8042).
> + */
> + struct mutex *ps2_cmd_mutex;
> };
> #define to_serio_port(d) container_of(d, struct serio, dev)
>
>
>
--
Dmitry
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