[PATCH v5 13/13] tty: gunyah: Add tty console driver for RM Console Services

Elliot Berman
2022-10-11T00:11:05Z

Gunyah provides a console for each VM using the VM console resource
manager APIs. This driver allows console data from other
VMs to be accessed via a TTY device and exports a console device to dump
Linux's own logs to our console.

Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
---
MAINTAINERS | 1 +
drivers/tty/Kconfig | 8 +
drivers/tty/Makefile | 1 +
drivers/tty/gunyah_console.c | 439 +++++++++++++++++++++++++++++++++++
4 files changed, 449 insertions(+)
create mode 100644 drivers/tty/gunyah_console.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 8a3d79b56698..e85140fa0dfe 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8889,6 +8889,7 @@ F: Documentation/devicetree/bindings/firmware/gunyah-hypervisor.yaml
F: Documentation/virt/gunyah/
F: arch/arm64/gunyah/
F: drivers/mailbox/gunyah-msgq.c
+F: drivers/tty/gunyah_tty.c
F: drivers/virt/gunyah/
F: include/asm-generic/gunyah.h
F: include/linux/gunyah*.h
diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
index cc30ff93e2e4..ff86e977f9ac 100644
--- a/drivers/tty/Kconfig
+++ b/drivers/tty/Kconfig
@@ -380,6 +380,14 @@ config RPMSG_TTY
To compile this driver as a module, choose M here: the module will be
called rpmsg_tty.

+config GUNYAH_CONSOLE
+ tristate "Gunyah Consoles"
+ depends on GUNYAH
+ help
+ This enables support for console output using Gunyah's Resource Manager RPC.
+ This is normally used when a secondary VM which does not have exclusive access
+ to a real or virtualized serial device and virtio-console is unavailable.
+
endif # TTY

source "drivers/tty/serdev/Kconfig"
diff --git a/drivers/tty/Makefile b/drivers/tty/Makefile
index 07aca5184a55..134b7321c630 100644
--- a/drivers/tty/Makefile
+++ b/drivers/tty/Makefile
@@ -27,5 +27,6 @@ obj-$(CONFIG_GOLDFISH_TTY) += goldfish.o
obj-$(CONFIG_MIPS_EJTAG_FDC_TTY) += mips_ejtag_fdc.o
obj-$(CONFIG_VCC) += vcc.o
obj-$(CONFIG_RPMSG_TTY) += rpmsg_tty.o
+obj-$(CONFIG_GUNYAH_CONSOLE) += gunyah_console.o

obj-y += ipwireless/
diff --git a/drivers/tty/gunyah_console.c b/drivers/tty/gunyah_console.c
new file mode 100644
index 000000000000..71d9f22c2a43
--- /dev/null
+++ b/drivers/tty/gunyah_console.c
@@ -0,0 +1,439 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+
+#include <linux/console.h>
+#include <linux/kfifo.h>
+#include <linux/kref.h>
+#include <linux/gunyah_rsc_mgr.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include <linux/workqueue.h>
+
+/*
+ * The Linux TTY code requires us to know ahead of time how many ports we might
+ * need. Each port here corresponds to a VM. 16 seems like a reasonable number
+ * of ports for systems that are running Gunyah and using the console interface.
+ */
+#define RM_CONS_TTY_ADAPATERS (16)
+
+struct rm_cons_port {
+ struct tty_port port;
+ u16 vmid;
+ unsigned int index;
+};
+
+struct rm_cons_drv_data {
+ struct tty_driver *tty_driver;
+ struct device *dev;
+
+ spinlock_t ports_lock;
+ struct rm_cons_port *ports[RM_CONS_TTY_ADAPATERS];
+
+ struct notifier_block rm_cons_notif;
+ struct console console;
+
+ /* below are for printk console.
+ * gh_rm_console_* calls will sleep and console_write can be called from
+ * atomic ctx. Two xmit buffers are used. The active buffer is tracked with
+ * co_xmit_idx. Writes go into the co_xmit_buf[co_xmit_idx] buffer.
+ * A work is scheduled to flush the bytes. The work will swap the active buffer
+ * and write out the other buffer.
+ */
+ char *co_xmit_buf[2];
+ int co_xmit_idx;
+ unsigned int co_xmit_count;
+ spinlock_t co_xmit_lock;
+ struct work_struct co_flush_work;
+};
+
+static int rm_cons_notif_handler(struct notifier_block *nb, unsigned long cmd, void *data)
+{
+ int count, i;
+ struct rm_cons_port *rm_port = NULL;
+ struct tty_port *tty_port = NULL;
+ struct rm_cons_drv_data *cons_data =
+ container_of(nb, struct rm_cons_drv_data, rm_cons_notif);
+ const struct gh_rm_notification *notif = data;
+ struct gh_rm_notif_vm_console_chars const * const msg = notif->buff;
+
+ if (cmd != GH_RM_NOTIF_VM_CONSOLE_CHARS ||
+ notif->size < sizeof(*msg))
+ return NOTIFY_DONE;
+
+ spin_lock(&cons_data->ports_lock);
+ for (i = 0; i < RM_CONS_TTY_ADAPATERS; i++) {
+ if (!cons_data->ports[i])
+ continue;
+ if (cons_data->ports[i]->vmid == msg->vmid) {
+ rm_port = cons_data->ports[i];
+ break;
+ }
+ }
+ if (rm_port)
+ tty_port = tty_port_get(&rm_port->port);
+ spin_unlock(&cons_data->ports_lock);
+
+ if (!rm_port)
+ dev_warn(cons_data->dev, "Received unexpected console characters for VMID %u\n",
+ msg->vmid);
+ if (!tty_port)
+ return NOTIFY_DONE;
+
+ count = tty_buffer_request_room(tty_port, msg->num_bytes);
+ tty_insert_flip_string(tty_port, msg->bytes, count);
+ tty_flip_buffer_push(tty_port);
+
+ tty_port_put(tty_port);
+ return NOTIFY_OK;
+}
+
+static int rm_cons_tty_open(struct tty_struct *tty, struct file *filp)
+{
+ struct rm_cons_port *rm_port = dev_get_drvdata(tty->dev);
+
+ return tty_port_open(&rm_port->port, tty, filp);
+}
+
+static void rm_cons_tty_close(struct tty_struct *tty, struct file *filp)
+{
+ struct rm_cons_port *rm_port = dev_get_drvdata(tty->dev);
+
+ tty_port_close(&rm_port->port, tty, filp);
+}
+
+static int rm_cons_tty_write(struct tty_struct *tty, const unsigned char *buf, int count)
+{
+ struct rm_cons_port *rm_port = dev_get_drvdata(tty->dev);
+ int ret;
+
+ if (!count)
+ return 0;
+
+ ret = gh_rm_console_write(rm_port->vmid, buf, count);
+ if (ret)
+ return -EAGAIN;
+ return count;
+}
+
+static void rm_cons_tty_flush_chars(struct tty_struct *tty)
+{
+ struct rm_cons_port *rm_port = dev_get_drvdata(tty->dev);
+
+ gh_rm_console_flush(rm_port->vmid);
+}
+
+static unsigned int rm_cons_mgr_tty_write_room(struct tty_struct *tty)
+{
+ return GH_RM_CONSOLE_WRITE_CHARS;
+}
+
+static const struct tty_operations rm_cons_tty_ops = {
+ .open = rm_cons_tty_open,
+ .close = rm_cons_tty_close,
+ .write = rm_cons_tty_write,
+ .flush_chars = rm_cons_tty_flush_chars,
+ .write_room = rm_cons_mgr_tty_write_room,
+};
+
+static int rm_cons_port_activate(struct tty_port *port, struct tty_struct *tty)
+{
+ struct rm_cons_port *rm_port = container_of(port, struct rm_cons_port, port);
+
+ return gh_rm_console_open(rm_port->vmid);
+}
+
+static void rm_cons_port_shutdown(struct tty_port *port)
+{
+ struct rm_cons_port *rm_port = container_of(port, struct rm_cons_port, port);
+ int ret;
+
+ ret = gh_rm_console_close(rm_port->vmid);
+ if (ret)
+ dev_err(port->tty->dev, "Failed to close ttyGH%d: %d\n", rm_port->index, ret);
+}
+
+static void rm_cons_port_destruct(struct tty_port *port)
+{
+ struct rm_cons_port *rm_port = container_of(port, struct rm_cons_port, port);
+ struct rm_cons_drv_data *cons_data = dev_get_drvdata(port->tty->dev);
+
+ spin_lock(&cons_data->ports_lock);
+ cons_data->ports[rm_port->index] = NULL;
+ spin_unlock(&cons_data->ports_lock);
+ kfree(rm_port);
+}
+
+static const struct tty_port_operations rm_cons_port_ops = {
+ .activate = rm_cons_port_activate,
+ .shutdown = rm_cons_port_shutdown,
+ .destruct = rm_cons_port_destruct,
+};
+
+static void rm_cons_console_flush_work(struct work_struct *ws)
+{
+ struct rm_cons_drv_data *cons_data =
+ container_of(ws, struct rm_cons_drv_data, co_flush_work);
+ struct console *co = &cons_data->console;
+ struct rm_cons_port *rm_port = co->data;
+ unsigned long flags;
+ size_t size;
+ int ret, old_buf = cons_data->co_xmit_idx;
+
+ spin_lock_irqsave(&cons_data->co_xmit_lock, flags);
+ cons_data->co_xmit_idx = 1 - old_buf;
+ size = cons_data->co_xmit_count;
+ cons_data->co_xmit_count = 0;
+ spin_unlock_irqrestore(&cons_data->co_xmit_lock, flags);
+
+ do {
+ ret = gh_rm_console_write(rm_port->vmid, cons_data->co_xmit_buf[old_buf], size);
+ } while (ret && ret != -ENOMEM);
+
+ gh_rm_console_flush(rm_port->vmid);
+}
+
+static void rm_cons_console_write(struct console *co, const char *buf, unsigned count)
+{
+ struct rm_cons_drv_data *cons_data = container_of(co, struct rm_cons_drv_data, console);
+ unsigned long flags;
+
+ spin_lock_irqsave(&cons_data->co_xmit_lock, flags);
+ count = min(count, (unsigned)(PAGE_SIZE - cons_data->co_xmit_count));
+ memcpy(&cons_data->co_xmit_buf[cons_data->co_xmit_idx][cons_data->co_xmit_count], buf,
+ count);
+ cons_data->co_xmit_count += count;
+ spin_unlock_irqrestore(&cons_data->co_xmit_lock, flags);
+
+ schedule_work(&cons_data->co_flush_work);
+}
+
+static struct tty_driver *rm_cons_console_device(struct console *co, int *index)
+{
+ struct rm_cons_drv_data *cons_data = container_of(co, struct rm_cons_drv_data, console);
+ struct rm_cons_port *rm_port = co->data;
+
+ *index = rm_port->index;
+ return cons_data->tty_driver;
+}
+
+static int rm_cons_console_setup(struct console *co, char *unused)
+{
+ struct rm_cons_drv_data *cons_data = container_of(co, struct rm_cons_drv_data, console);
+ struct rm_cons_port *rm_port = co->data;
+ int ret;
+
+ if (!tty_port_get(&rm_port->port))
+ return -ENODEV;
+
+ cons_data->co_xmit_buf[0] = (unsigned char *)get_zeroed_page(GFP_KERNEL);
+ if (!cons_data->co_xmit_buf[0])
+ goto err;
+ cons_data->co_xmit_buf[1] = (unsigned char *)get_zeroed_page(GFP_KERNEL);
+ if (!cons_data->co_xmit_buf[1])
+ goto err;
+
+ mutex_lock(&rm_port->port.mutex);
+ if (!tty_port_initialized(&rm_port->port)) {
+ ret = gh_rm_console_open(rm_port->vmid);
+ if (ret) {
+ dev_err(rm_port->port.tty->dev, "Failed to open %s%d: %d\n",
+ co->name, rm_port->index, ret);
+ goto err;
+ }
+ tty_port_set_initialized(&rm_port->port, true);
+ }
+ rm_port->port.console = true;
+ mutex_unlock(&rm_port->port.mutex);
+
+ return 0;
+err:
+ if (cons_data->co_xmit_buf[1])
+ free_page((unsigned long)cons_data->co_xmit_buf[1]);
+ if (cons_data->co_xmit_buf[0])
+ free_page((unsigned long)cons_data->co_xmit_buf[0]);
+ mutex_unlock(&rm_port->port.mutex);
+ tty_port_put(&rm_port->port);
+ return ret;
+}
+
+static int rm_cons_console_exit(struct console *co)
+{
+ struct rm_cons_port *rm_port = co->data;
+ int ret;
+
+ mutex_lock(&rm_port->port.mutex);
+ rm_port->port.console = false;
+
+ if (!tty_port_active(&rm_port->port)) {
+ ret = gh_rm_console_close(rm_port->vmid);
+ if (ret)
+ dev_err(rm_port->port.tty->dev, "Failed to close %s%d: %d\n",
+ co->name, rm_port->index, ret);
+ tty_port_set_initialized(&rm_port->port, false);
+ }
+
+ mutex_unlock(&rm_port->port.mutex);
+ tty_port_put(&rm_port->port);
+
+ return 0;
+}
+
+static struct rm_cons_port *rm_cons_port_create(struct rm_cons_drv_data *cons_data, u16 vmid)
+{
+ struct rm_cons_port *rm_port;
+ struct device *ttydev;
+ unsigned int index;
+ int ret;
+
+ rm_port = kzalloc(sizeof(*rm_port), GFP_KERNEL);
+ if (!rm_port)
+ return ERR_PTR(-ENOMEM);
+ rm_port->vmid = vmid;
+ tty_port_init(&rm_port->port);
+ rm_port->port.ops = &rm_cons_port_ops;
+
+ spin_lock(&cons_data->ports_lock);
+ for (index = 0; index < RM_CONS_TTY_ADAPATERS; index++) {
+ if (!cons_data->ports[index]) {
+ cons_data->ports[index] = rm_port;
+ rm_port->index = index;
+ break;
+ }
+ }
+ spin_unlock(&cons_data->ports_lock);
+ if (index >= RM_CONS_TTY_ADAPATERS) {
+ ret = -ENOSPC;
+ goto err_put_port;
+ }
+
+ ttydev = tty_port_register_device_attr(&rm_port->port, cons_data->tty_driver, index,
+ cons_data->dev, rm_port, NULL);
+ if (IS_ERR(ttydev)) {
+ ret = PTR_ERR(ttydev);
+ goto err_put_port;
+ }
+
+ return rm_port;
+err_put_port:
+ tty_port_put(&rm_port->port);
+ return ERR_PTR(ret);
+}
+
+static int rm_cons_console_probe(struct device *dev)
+{
+ struct rm_cons_drv_data *cons_data;
+ struct rm_cons_port *rm_port;
+ int ret;
+ u16 vmid;
+
+ cons_data = devm_kzalloc(dev, sizeof(*cons_data), GFP_KERNEL);
+ if (!cons_data)
+ return -ENOMEM;
+ dev_set_drvdata(dev, cons_data);
+ cons_data->dev = dev;
+
+ cons_data->tty_driver = tty_alloc_driver(RM_CONS_TTY_ADAPATERS,
+ TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV |
+ TTY_DRIVER_RESET_TERMIOS);
+ if (IS_ERR(cons_data->tty_driver))
+ return PTR_ERR(cons_data->tty_driver);
+
+ cons_data->tty_driver->driver_name = KBUILD_MODNAME;
+ cons_data->tty_driver->name = "ttyGH";
+ cons_data->tty_driver->type = TTY_DRIVER_TYPE_SYSTEM;
+ cons_data->tty_driver->subtype = SYSTEM_TYPE_TTY;
+ cons_data->tty_driver->init_termios = tty_std_termios;
+ tty_set_operations(cons_data->tty_driver, &rm_cons_tty_ops);
+
+ ret = tty_register_driver(cons_data->tty_driver);
+ if (ret) {
+ dev_err(dev, "Could not register tty driver: %d\n", ret);
+ goto err_put_tty;
+ }
+
+ spin_lock_init(&cons_data->ports_lock);
+
+ cons_data->rm_cons_notif.notifier_call = rm_cons_notif_handler;
+ ret = gh_rm_register_notifier(&cons_data->rm_cons_notif);
+ if (ret) {
+ dev_err(dev, "Could not register for resource manager notifications: %d\n", ret);
+ goto err_put_tty;
+ }
+
+ spin_lock_init(&cons_data->co_xmit_lock);
+ INIT_WORK(&cons_data->co_flush_work, rm_cons_console_flush_work);
+
+ rm_port = rm_cons_port_create(cons_data, GH_VMID_SELF);
+ if (IS_ERR(rm_port)) {
+ ret = PTR_ERR(rm_port);
+ dev_err(dev, "Could not create own console: %d\n", ret);
+ goto err_unreg_notif;
+ }
+
+ rm_port->port.console = 1;
+ strncpy(cons_data->console.name, "ttyGH", sizeof(cons_data->console.name));
+ cons_data->console.write = rm_cons_console_write;
+ cons_data->console.device = rm_cons_console_device;
+ cons_data->console.setup = rm_cons_console_setup;
+ cons_data->console.exit = rm_cons_console_exit;
+ cons_data->console.index = rm_port->index;
+ cons_data->console.data = rm_port;
+ register_console(&cons_data->console);
+
+ ret = gh_rm_get_vmid(&vmid);
+ if (!ret) {
+ rm_port = rm_cons_port_create(cons_data, vmid);
+ if (IS_ERR(rm_port))
+ dev_warn(dev, "Could not create loopback console: %ld\n", PTR_ERR(rm_port));
+ } else {
+ dev_warn(dev, "Failed to get this VM's VMID: %d. Not creating loop-back console\n",
+ ret);
+ }
+
+ return 0;
+err_unreg_notif:
+ gh_rm_unregister_notifier(&cons_data->rm_cons_notif);
+err_put_tty:
+ tty_driver_kref_put(cons_data->tty_driver);
+ return ret;
+}
+
+static int rm_cons_console_remove(struct device *dev)
+{
+ struct rm_cons_drv_data *cons_data = dev_get_drvdata(dev);
+
+ unregister_console(&cons_data->console);
+ if (cons_data->co_xmit_buf[1])
+ free_page((unsigned long)cons_data->co_xmit_buf[1]);
+ if (cons_data->co_xmit_buf[0])
+ free_page((unsigned long)cons_data->co_xmit_buf[0]);
+ gh_rm_unregister_notifier(&cons_data->rm_cons_notif);
+ tty_unregister_driver(cons_data->tty_driver);
+ tty_driver_kref_put(cons_data->tty_driver);
+
+ return 0;
+}
+
+static struct gunyah_rm_cons_device_id rm_cons_console_ids[] = {
+ { .name = GH_RM_DEVICE_CONSOLE },
+ {}
+};
+MODULE_DEVICE_TABLE(gunyah_rsc_mgr, rm_cons_console_ids);
+
+static struct gh_rm_driver rm_cons_console_drv = {
+ .drv = {
+ .name = KBUILD_MODNAME,
+ .probe = rm_cons_console_probe,
+ .remove = rm_cons_console_remove,
+ },
+ .id_table = rm_cons_console_ids,
+};
+module_gh_rm_driver(rm_cons_console_drv);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Gunyah Console");
--
2.25.1