xref: /linux/drivers/platform/goldfish/goldfish_pipe.c (revision a1ff5a7d78a036d6c2178ee5acd6ba4946243800)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) 2012 Intel, Inc.
4  * Copyright (C) 2013 Intel, Inc.
5  * Copyright (C) 2014 Linaro Limited
6  * Copyright (C) 2011-2016 Google, Inc.
7  *
8  * This software is licensed under the terms of the GNU General Public
9  * License version 2, as published by the Free Software Foundation, and
10  * may be copied, distributed, and modified under those terms.
11  *
12  * This program is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15  * GNU General Public License for more details.
16  *
17  */
18 
19 /* This source file contains the implementation of a special device driver
20  * that intends to provide a *very* fast communication channel between the
21  * guest system and the QEMU emulator.
22  *
23  * Usage from the guest is simply the following (error handling simplified):
24  *
25  *    int  fd = open("/dev/qemu_pipe",O_RDWR);
26  *    .... write() or read() through the pipe.
27  *
28  * This driver doesn't deal with the exact protocol used during the session.
29  * It is intended to be as simple as something like:
30  *
31  *    // do this _just_ after opening the fd to connect to a specific
32  *    // emulator service.
33  *    const char*  msg = "<pipename>";
34  *    if (write(fd, msg, strlen(msg)+1) < 0) {
35  *       ... could not connect to <pipename> service
36  *       close(fd);
37  *    }
38  *
39  *    // after this, simply read() and write() to communicate with the
40  *    // service. Exact protocol details left as an exercise to the reader.
41  *
42  * This driver is very fast because it doesn't copy any data through
43  * intermediate buffers, since the emulator is capable of translating
44  * guest user addresses into host ones.
45  *
46  * Note that we must however ensure that each user page involved in the
47  * exchange is properly mapped during a transfer.
48  */
49 
50 #include <linux/module.h>
51 #include <linux/mod_devicetable.h>
52 #include <linux/interrupt.h>
53 #include <linux/kernel.h>
54 #include <linux/spinlock.h>
55 #include <linux/miscdevice.h>
56 #include <linux/platform_device.h>
57 #include <linux/poll.h>
58 #include <linux/sched.h>
59 #include <linux/bitops.h>
60 #include <linux/slab.h>
61 #include <linux/io.h>
62 #include <linux/dma-mapping.h>
63 #include <linux/mm.h>
64 #include <linux/acpi.h>
65 #include <linux/bug.h>
66 #include "goldfish_pipe_qemu.h"
67 
68 /*
69  * Update this when something changes in the driver's behavior so the host
70  * can benefit from knowing it
71  */
72 enum {
73 	PIPE_DRIVER_VERSION = 2,
74 	PIPE_CURRENT_DEVICE_VERSION = 2
75 };
76 
77 enum {
78 	MAX_BUFFERS_PER_COMMAND = 336,
79 	MAX_SIGNALLED_PIPES = 64,
80 	INITIAL_PIPES_CAPACITY = 64
81 };
82 
83 struct goldfish_pipe_dev;
84 
85 /* A per-pipe command structure, shared with the host */
86 struct goldfish_pipe_command {
87 	s32 cmd;	/* PipeCmdCode, guest -> host */
88 	s32 id;		/* pipe id, guest -> host */
89 	s32 status;	/* command execution status, host -> guest */
90 	s32 reserved;	/* to pad to 64-bit boundary */
91 	union {
92 		/* Parameters for PIPE_CMD_{READ,WRITE} */
93 		struct {
94 			/* number of buffers, guest -> host */
95 			u32 buffers_count;
96 			/* number of consumed bytes, host -> guest */
97 			s32 consumed_size;
98 			/* buffer pointers, guest -> host */
99 			u64 ptrs[MAX_BUFFERS_PER_COMMAND];
100 			/* buffer sizes, guest -> host */
101 			u32 sizes[MAX_BUFFERS_PER_COMMAND];
102 		} rw_params;
103 	};
104 };
105 
106 /* A single signalled pipe information */
107 struct signalled_pipe_buffer {
108 	u32 id;
109 	u32 flags;
110 };
111 
112 /* Parameters for the PIPE_CMD_OPEN command */
113 struct open_command_param {
114 	u64 command_buffer_ptr;
115 	u32 rw_params_max_count;
116 };
117 
118 /* Device-level set of buffers shared with the host */
119 struct goldfish_pipe_dev_buffers {
120 	struct open_command_param open_command_params;
121 	struct signalled_pipe_buffer
122 		signalled_pipe_buffers[MAX_SIGNALLED_PIPES];
123 };
124 
125 /* This data type models a given pipe instance */
126 struct goldfish_pipe {
127 	/* pipe ID - index into goldfish_pipe_dev::pipes array */
128 	u32 id;
129 
130 	/* The wake flags pipe is waiting for
131 	 * Note: not protected with any lock, uses atomic operations
132 	 *  and barriers to make it thread-safe.
133 	 */
134 	unsigned long flags;
135 
136 	/* wake flags host have signalled,
137 	 *  - protected by goldfish_pipe_dev::lock
138 	 */
139 	unsigned long signalled_flags;
140 
141 	/* A pointer to command buffer */
142 	struct goldfish_pipe_command *command_buffer;
143 
144 	/* doubly linked list of signalled pipes, protected by
145 	 * goldfish_pipe_dev::lock
146 	 */
147 	struct goldfish_pipe *prev_signalled;
148 	struct goldfish_pipe *next_signalled;
149 
150 	/*
151 	 * A pipe's own lock. Protects the following:
152 	 *  - *command_buffer - makes sure a command can safely write its
153 	 *    parameters to the host and read the results back.
154 	 */
155 	struct mutex lock;
156 
157 	/* A wake queue for sleeping until host signals an event */
158 	wait_queue_head_t wake_queue;
159 
160 	/* Pointer to the parent goldfish_pipe_dev instance */
161 	struct goldfish_pipe_dev *dev;
162 
163 	/* A buffer of pages, too large to fit into a stack frame */
164 	struct page *pages[MAX_BUFFERS_PER_COMMAND];
165 };
166 
167 /* The global driver data. Holds a reference to the i/o page used to
168  * communicate with the emulator, and a wake queue for blocked tasks
169  * waiting to be awoken.
170  */
171 struct goldfish_pipe_dev {
172 	/* A magic number to check if this is an instance of this struct */
173 	void *magic;
174 
175 	/*
176 	 * Global device spinlock. Protects the following members:
177 	 *  - pipes, pipes_capacity
178 	 *  - [*pipes, *pipes + pipes_capacity) - array data
179 	 *  - first_signalled_pipe,
180 	 *      goldfish_pipe::prev_signalled,
181 	 *      goldfish_pipe::next_signalled,
182 	 *      goldfish_pipe::signalled_flags - all singnalled-related fields,
183 	 *                                       in all allocated pipes
184 	 *  - open_command_params - PIPE_CMD_OPEN-related buffers
185 	 *
186 	 * It looks like a lot of different fields, but the trick is that
187 	 * the only operation that happens often is the signalled pipes array
188 	 * manipulation. That's why it's OK for now to keep the rest of the
189 	 * fields under the same lock. If we notice too much contention because
190 	 * of PIPE_CMD_OPEN, then we should add a separate lock there.
191 	 */
192 	spinlock_t lock;
193 
194 	/*
195 	 * Array of the pipes of |pipes_capacity| elements,
196 	 * indexed by goldfish_pipe::id
197 	 */
198 	struct goldfish_pipe **pipes;
199 	u32 pipes_capacity;
200 
201 	/* Pointers to the buffers host uses for interaction with this driver */
202 	struct goldfish_pipe_dev_buffers *buffers;
203 
204 	/* Head of a doubly linked list of signalled pipes */
205 	struct goldfish_pipe *first_signalled_pipe;
206 
207 	/* ptr to platform device's device struct */
208 	struct device *pdev_dev;
209 
210 	/* Some device-specific data */
211 	int irq;
212 	int version;
213 	unsigned char __iomem *base;
214 
215 	struct miscdevice miscdev;
216 };
217 
goldfish_pipe_cmd_locked(struct goldfish_pipe * pipe,enum PipeCmdCode cmd)218 static int goldfish_pipe_cmd_locked(struct goldfish_pipe *pipe,
219 				    enum PipeCmdCode cmd)
220 {
221 	pipe->command_buffer->cmd = cmd;
222 	/* failure by default */
223 	pipe->command_buffer->status = PIPE_ERROR_INVAL;
224 	writel(pipe->id, pipe->dev->base + PIPE_REG_CMD);
225 	return pipe->command_buffer->status;
226 }
227 
goldfish_pipe_cmd(struct goldfish_pipe * pipe,enum PipeCmdCode cmd)228 static int goldfish_pipe_cmd(struct goldfish_pipe *pipe, enum PipeCmdCode cmd)
229 {
230 	int status;
231 
232 	if (mutex_lock_interruptible(&pipe->lock))
233 		return PIPE_ERROR_IO;
234 	status = goldfish_pipe_cmd_locked(pipe, cmd);
235 	mutex_unlock(&pipe->lock);
236 	return status;
237 }
238 
239 /*
240  * This function converts an error code returned by the emulator through
241  * the PIPE_REG_STATUS i/o register into a valid negative errno value.
242  */
goldfish_pipe_error_convert(int status)243 static int goldfish_pipe_error_convert(int status)
244 {
245 	switch (status) {
246 	case PIPE_ERROR_AGAIN:
247 		return -EAGAIN;
248 	case PIPE_ERROR_NOMEM:
249 		return -ENOMEM;
250 	case PIPE_ERROR_IO:
251 		return -EIO;
252 	default:
253 		return -EINVAL;
254 	}
255 }
256 
goldfish_pin_pages(unsigned long first_page,unsigned long last_page,unsigned int last_page_size,int is_write,struct page * pages[MAX_BUFFERS_PER_COMMAND],unsigned int * iter_last_page_size)257 static int goldfish_pin_pages(unsigned long first_page,
258 			      unsigned long last_page,
259 			      unsigned int last_page_size,
260 			      int is_write,
261 			      struct page *pages[MAX_BUFFERS_PER_COMMAND],
262 			      unsigned int *iter_last_page_size)
263 {
264 	int ret;
265 	int requested_pages = ((last_page - first_page) >> PAGE_SHIFT) + 1;
266 
267 	if (requested_pages > MAX_BUFFERS_PER_COMMAND) {
268 		requested_pages = MAX_BUFFERS_PER_COMMAND;
269 		*iter_last_page_size = PAGE_SIZE;
270 	} else {
271 		*iter_last_page_size = last_page_size;
272 	}
273 
274 	ret = pin_user_pages_fast(first_page, requested_pages,
275 				  !is_write ? FOLL_WRITE : 0,
276 				  pages);
277 	if (ret <= 0)
278 		return -EFAULT;
279 	if (ret < requested_pages)
280 		*iter_last_page_size = PAGE_SIZE;
281 
282 	return ret;
283 }
284 
285 /* Populate the call parameters, merging adjacent pages together */
populate_rw_params(struct page ** pages,int pages_count,unsigned long address,unsigned long address_end,unsigned long first_page,unsigned long last_page,unsigned int iter_last_page_size,int is_write,struct goldfish_pipe_command * command)286 static void populate_rw_params(struct page **pages,
287 			       int pages_count,
288 			       unsigned long address,
289 			       unsigned long address_end,
290 			       unsigned long first_page,
291 			       unsigned long last_page,
292 			       unsigned int iter_last_page_size,
293 			       int is_write,
294 			       struct goldfish_pipe_command *command)
295 {
296 	/*
297 	 * Process the first page separately - it's the only page that
298 	 * needs special handling for its start address.
299 	 */
300 	unsigned long xaddr = page_to_phys(pages[0]);
301 	unsigned long xaddr_prev = xaddr;
302 	int buffer_idx = 0;
303 	int i = 1;
304 	int size_on_page = first_page == last_page
305 			? (int)(address_end - address)
306 			: (PAGE_SIZE - (address & ~PAGE_MASK));
307 	command->rw_params.ptrs[0] = (u64)(xaddr | (address & ~PAGE_MASK));
308 	command->rw_params.sizes[0] = size_on_page;
309 	for (; i < pages_count; ++i) {
310 		xaddr = page_to_phys(pages[i]);
311 		size_on_page = (i == pages_count - 1) ?
312 			iter_last_page_size : PAGE_SIZE;
313 		if (xaddr == xaddr_prev + PAGE_SIZE) {
314 			command->rw_params.sizes[buffer_idx] += size_on_page;
315 		} else {
316 			++buffer_idx;
317 			command->rw_params.ptrs[buffer_idx] = (u64)xaddr;
318 			command->rw_params.sizes[buffer_idx] = size_on_page;
319 		}
320 		xaddr_prev = xaddr;
321 	}
322 	command->rw_params.buffers_count = buffer_idx + 1;
323 }
324 
transfer_max_buffers(struct goldfish_pipe * pipe,unsigned long address,unsigned long address_end,int is_write,unsigned long last_page,unsigned int last_page_size,s32 * consumed_size,int * status)325 static int transfer_max_buffers(struct goldfish_pipe *pipe,
326 				unsigned long address,
327 				unsigned long address_end,
328 				int is_write,
329 				unsigned long last_page,
330 				unsigned int last_page_size,
331 				s32 *consumed_size,
332 				int *status)
333 {
334 	unsigned long first_page = address & PAGE_MASK;
335 	unsigned int iter_last_page_size;
336 	int pages_count;
337 
338 	/* Serialize access to the pipe command buffers */
339 	if (mutex_lock_interruptible(&pipe->lock))
340 		return -ERESTARTSYS;
341 
342 	pages_count = goldfish_pin_pages(first_page, last_page,
343 					 last_page_size, is_write,
344 					 pipe->pages, &iter_last_page_size);
345 	if (pages_count < 0) {
346 		mutex_unlock(&pipe->lock);
347 		return pages_count;
348 	}
349 
350 	populate_rw_params(pipe->pages, pages_count, address, address_end,
351 			   first_page, last_page, iter_last_page_size, is_write,
352 			   pipe->command_buffer);
353 
354 	/* Transfer the data */
355 	*status = goldfish_pipe_cmd_locked(pipe,
356 				is_write ? PIPE_CMD_WRITE : PIPE_CMD_READ);
357 
358 	*consumed_size = pipe->command_buffer->rw_params.consumed_size;
359 
360 	unpin_user_pages_dirty_lock(pipe->pages, pages_count,
361 				    !is_write && *consumed_size > 0);
362 
363 	mutex_unlock(&pipe->lock);
364 	return 0;
365 }
366 
wait_for_host_signal(struct goldfish_pipe * pipe,int is_write)367 static int wait_for_host_signal(struct goldfish_pipe *pipe, int is_write)
368 {
369 	u32 wake_bit = is_write ? BIT_WAKE_ON_WRITE : BIT_WAKE_ON_READ;
370 
371 	set_bit(wake_bit, &pipe->flags);
372 
373 	/* Tell the emulator we're going to wait for a wake event */
374 	goldfish_pipe_cmd(pipe,
375 		is_write ? PIPE_CMD_WAKE_ON_WRITE : PIPE_CMD_WAKE_ON_READ);
376 
377 	while (test_bit(wake_bit, &pipe->flags)) {
378 		if (wait_event_interruptible(pipe->wake_queue,
379 					     !test_bit(wake_bit, &pipe->flags)))
380 			return -ERESTARTSYS;
381 
382 		if (test_bit(BIT_CLOSED_ON_HOST, &pipe->flags))
383 			return -EIO;
384 	}
385 
386 	return 0;
387 }
388 
goldfish_pipe_read_write(struct file * filp,char __user * buffer,size_t bufflen,int is_write)389 static ssize_t goldfish_pipe_read_write(struct file *filp,
390 					char __user *buffer,
391 					size_t bufflen,
392 					int is_write)
393 {
394 	struct goldfish_pipe *pipe = filp->private_data;
395 	int count = 0, ret = -EINVAL;
396 	unsigned long address, address_end, last_page;
397 	unsigned int last_page_size;
398 
399 	/* If the emulator already closed the pipe, no need to go further */
400 	if (unlikely(test_bit(BIT_CLOSED_ON_HOST, &pipe->flags)))
401 		return -EIO;
402 	/* Null reads or writes succeeds */
403 	if (unlikely(bufflen == 0))
404 		return 0;
405 	/* Check the buffer range for access */
406 	if (unlikely(!access_ok(buffer, bufflen)))
407 		return -EFAULT;
408 
409 	address = (unsigned long)buffer;
410 	address_end = address + bufflen;
411 	last_page = (address_end - 1) & PAGE_MASK;
412 	last_page_size = ((address_end - 1) & ~PAGE_MASK) + 1;
413 
414 	while (address < address_end) {
415 		s32 consumed_size;
416 		int status;
417 
418 		ret = transfer_max_buffers(pipe, address, address_end, is_write,
419 					   last_page, last_page_size,
420 					   &consumed_size, &status);
421 		if (ret < 0)
422 			break;
423 
424 		if (consumed_size > 0) {
425 			/* No matter what's the status, we've transferred
426 			 * something.
427 			 */
428 			count += consumed_size;
429 			address += consumed_size;
430 		}
431 		if (status > 0)
432 			continue;
433 		if (status == 0) {
434 			/* EOF */
435 			ret = 0;
436 			break;
437 		}
438 		if (count > 0) {
439 			/*
440 			 * An error occurred, but we already transferred
441 			 * something on one of the previous iterations.
442 			 * Just return what we already copied and log this
443 			 * err.
444 			 */
445 			if (status != PIPE_ERROR_AGAIN)
446 				dev_err_ratelimited(pipe->dev->pdev_dev,
447 					"backend error %d on %s\n",
448 					status, is_write ? "write" : "read");
449 			break;
450 		}
451 
452 		/*
453 		 * If the error is not PIPE_ERROR_AGAIN, or if we are in
454 		 * non-blocking mode, just return the error code.
455 		 */
456 		if (status != PIPE_ERROR_AGAIN ||
457 			(filp->f_flags & O_NONBLOCK) != 0) {
458 			ret = goldfish_pipe_error_convert(status);
459 			break;
460 		}
461 
462 		status = wait_for_host_signal(pipe, is_write);
463 		if (status < 0)
464 			return status;
465 	}
466 
467 	if (count > 0)
468 		return count;
469 	return ret;
470 }
471 
goldfish_pipe_read(struct file * filp,char __user * buffer,size_t bufflen,loff_t * ppos)472 static ssize_t goldfish_pipe_read(struct file *filp, char __user *buffer,
473 				  size_t bufflen, loff_t *ppos)
474 {
475 	return goldfish_pipe_read_write(filp, buffer, bufflen,
476 					/* is_write */ 0);
477 }
478 
goldfish_pipe_write(struct file * filp,const char __user * buffer,size_t bufflen,loff_t * ppos)479 static ssize_t goldfish_pipe_write(struct file *filp,
480 				   const char __user *buffer, size_t bufflen,
481 				   loff_t *ppos)
482 {
483 	/* cast away the const */
484 	char __user *no_const_buffer = (char __user *)buffer;
485 
486 	return goldfish_pipe_read_write(filp, no_const_buffer, bufflen,
487 					/* is_write */ 1);
488 }
489 
goldfish_pipe_poll(struct file * filp,poll_table * wait)490 static __poll_t goldfish_pipe_poll(struct file *filp, poll_table *wait)
491 {
492 	struct goldfish_pipe *pipe = filp->private_data;
493 	__poll_t mask = 0;
494 	int status;
495 
496 	poll_wait(filp, &pipe->wake_queue, wait);
497 
498 	status = goldfish_pipe_cmd(pipe, PIPE_CMD_POLL);
499 	if (status < 0)
500 		return -ERESTARTSYS;
501 
502 	if (status & PIPE_POLL_IN)
503 		mask |= EPOLLIN | EPOLLRDNORM;
504 	if (status & PIPE_POLL_OUT)
505 		mask |= EPOLLOUT | EPOLLWRNORM;
506 	if (status & PIPE_POLL_HUP)
507 		mask |= EPOLLHUP;
508 	if (test_bit(BIT_CLOSED_ON_HOST, &pipe->flags))
509 		mask |= EPOLLERR;
510 
511 	return mask;
512 }
513 
signalled_pipes_add_locked(struct goldfish_pipe_dev * dev,u32 id,u32 flags)514 static void signalled_pipes_add_locked(struct goldfish_pipe_dev *dev,
515 				       u32 id, u32 flags)
516 {
517 	struct goldfish_pipe *pipe;
518 
519 	if (WARN_ON(id >= dev->pipes_capacity))
520 		return;
521 
522 	pipe = dev->pipes[id];
523 	if (!pipe)
524 		return;
525 	pipe->signalled_flags |= flags;
526 
527 	if (pipe->prev_signalled || pipe->next_signalled ||
528 		dev->first_signalled_pipe == pipe)
529 		return;	/* already in the list */
530 	pipe->next_signalled = dev->first_signalled_pipe;
531 	if (dev->first_signalled_pipe)
532 		dev->first_signalled_pipe->prev_signalled = pipe;
533 	dev->first_signalled_pipe = pipe;
534 }
535 
signalled_pipes_remove_locked(struct goldfish_pipe_dev * dev,struct goldfish_pipe * pipe)536 static void signalled_pipes_remove_locked(struct goldfish_pipe_dev *dev,
537 					  struct goldfish_pipe *pipe)
538 {
539 	if (pipe->prev_signalled)
540 		pipe->prev_signalled->next_signalled = pipe->next_signalled;
541 	if (pipe->next_signalled)
542 		pipe->next_signalled->prev_signalled = pipe->prev_signalled;
543 	if (pipe == dev->first_signalled_pipe)
544 		dev->first_signalled_pipe = pipe->next_signalled;
545 	pipe->prev_signalled = NULL;
546 	pipe->next_signalled = NULL;
547 }
548 
signalled_pipes_pop_front(struct goldfish_pipe_dev * dev,int * wakes)549 static struct goldfish_pipe *signalled_pipes_pop_front(
550 		struct goldfish_pipe_dev *dev, int *wakes)
551 {
552 	struct goldfish_pipe *pipe;
553 	unsigned long flags;
554 
555 	spin_lock_irqsave(&dev->lock, flags);
556 
557 	pipe = dev->first_signalled_pipe;
558 	if (pipe) {
559 		*wakes = pipe->signalled_flags;
560 		pipe->signalled_flags = 0;
561 		/*
562 		 * This is an optimized version of
563 		 * signalled_pipes_remove_locked()
564 		 * - We want to make it as fast as possible to
565 		 * wake the sleeping pipe operations faster.
566 		 */
567 		dev->first_signalled_pipe = pipe->next_signalled;
568 		if (dev->first_signalled_pipe)
569 			dev->first_signalled_pipe->prev_signalled = NULL;
570 		pipe->next_signalled = NULL;
571 	}
572 
573 	spin_unlock_irqrestore(&dev->lock, flags);
574 	return pipe;
575 }
576 
goldfish_interrupt_task(int irq,void * dev_addr)577 static irqreturn_t goldfish_interrupt_task(int irq, void *dev_addr)
578 {
579 	/* Iterate over the signalled pipes and wake them one by one */
580 	struct goldfish_pipe_dev *dev = dev_addr;
581 	struct goldfish_pipe *pipe;
582 	int wakes;
583 
584 	while ((pipe = signalled_pipes_pop_front(dev, &wakes)) != NULL) {
585 		if (wakes & PIPE_WAKE_CLOSED) {
586 			pipe->flags = 1 << BIT_CLOSED_ON_HOST;
587 		} else {
588 			if (wakes & PIPE_WAKE_READ)
589 				clear_bit(BIT_WAKE_ON_READ, &pipe->flags);
590 			if (wakes & PIPE_WAKE_WRITE)
591 				clear_bit(BIT_WAKE_ON_WRITE, &pipe->flags);
592 		}
593 		/*
594 		 * wake_up_interruptible() implies a write barrier, so don't
595 		 * explicitly add another one here.
596 		 */
597 		wake_up_interruptible(&pipe->wake_queue);
598 	}
599 	return IRQ_HANDLED;
600 }
601 
602 static void goldfish_pipe_device_deinit(struct platform_device *pdev,
603 					struct goldfish_pipe_dev *dev);
604 
605 /*
606  * The general idea of the (threaded) interrupt handling:
607  *
608  *  1. device raises an interrupt if there's at least one signalled pipe
609  *  2. IRQ handler reads the signalled pipes and their count from the device
610  *  3. device writes them into a shared buffer and returns the count
611  *      it only resets the IRQ if it has returned all signalled pipes,
612  *      otherwise it leaves it raised, so IRQ handler will be called
613  *      again for the next chunk
614  *  4. IRQ handler adds all returned pipes to the device's signalled pipes list
615  *  5. IRQ handler defers processing the signalled pipes from the list in a
616  *      separate context
617  */
goldfish_pipe_interrupt(int irq,void * dev_id)618 static irqreturn_t goldfish_pipe_interrupt(int irq, void *dev_id)
619 {
620 	u32 count;
621 	u32 i;
622 	unsigned long flags;
623 	struct goldfish_pipe_dev *dev = dev_id;
624 
625 	if (dev->magic != &goldfish_pipe_device_deinit)
626 		return IRQ_NONE;
627 
628 	/* Request the signalled pipes from the device */
629 	spin_lock_irqsave(&dev->lock, flags);
630 
631 	count = readl(dev->base + PIPE_REG_GET_SIGNALLED);
632 	if (count == 0) {
633 		spin_unlock_irqrestore(&dev->lock, flags);
634 		return IRQ_NONE;
635 	}
636 	if (count > MAX_SIGNALLED_PIPES)
637 		count = MAX_SIGNALLED_PIPES;
638 
639 	for (i = 0; i < count; ++i)
640 		signalled_pipes_add_locked(dev,
641 			dev->buffers->signalled_pipe_buffers[i].id,
642 			dev->buffers->signalled_pipe_buffers[i].flags);
643 
644 	spin_unlock_irqrestore(&dev->lock, flags);
645 
646 	return IRQ_WAKE_THREAD;
647 }
648 
get_free_pipe_id_locked(struct goldfish_pipe_dev * dev)649 static int get_free_pipe_id_locked(struct goldfish_pipe_dev *dev)
650 {
651 	int id;
652 
653 	for (id = 0; id < dev->pipes_capacity; ++id)
654 		if (!dev->pipes[id])
655 			return id;
656 
657 	{
658 		/* Reallocate the array.
659 		 * Since get_free_pipe_id_locked runs with interrupts disabled,
660 		 * we don't want to make calls that could lead to sleep.
661 		 */
662 		u32 new_capacity = 2 * dev->pipes_capacity;
663 		struct goldfish_pipe **pipes =
664 			kcalloc(new_capacity, sizeof(*pipes), GFP_ATOMIC);
665 		if (!pipes)
666 			return -ENOMEM;
667 		memcpy(pipes, dev->pipes, sizeof(*pipes) * dev->pipes_capacity);
668 		kfree(dev->pipes);
669 		dev->pipes = pipes;
670 		id = dev->pipes_capacity;
671 		dev->pipes_capacity = new_capacity;
672 	}
673 	return id;
674 }
675 
676 /* A helper function to get the instance of goldfish_pipe_dev from file */
to_goldfish_pipe_dev(struct file * file)677 static struct goldfish_pipe_dev *to_goldfish_pipe_dev(struct file *file)
678 {
679 	struct miscdevice *miscdev = file->private_data;
680 
681 	return container_of(miscdev, struct goldfish_pipe_dev, miscdev);
682 }
683 
684 /**
685  *	goldfish_pipe_open - open a channel to the AVD
686  *	@inode: inode of device
687  *	@file: file struct of opener
688  *
689  *	Create a new pipe link between the emulator and the use application.
690  *	Each new request produces a new pipe.
691  *
692  *	Note: we use the pipe ID as a mux. All goldfish emulations are 32bit
693  *	right now so this is fine. A move to 64bit will need this addressing
694  */
goldfish_pipe_open(struct inode * inode,struct file * file)695 static int goldfish_pipe_open(struct inode *inode, struct file *file)
696 {
697 	struct goldfish_pipe_dev *dev = to_goldfish_pipe_dev(file);
698 	unsigned long flags;
699 	int id;
700 	int status;
701 
702 	/* Allocate new pipe kernel object */
703 	struct goldfish_pipe *pipe = kzalloc(sizeof(*pipe), GFP_KERNEL);
704 
705 	if (!pipe)
706 		return -ENOMEM;
707 
708 	pipe->dev = dev;
709 	mutex_init(&pipe->lock);
710 	init_waitqueue_head(&pipe->wake_queue);
711 
712 	/*
713 	 * Command buffer needs to be allocated on its own page to make sure
714 	 * it is physically contiguous in host's address space.
715 	 */
716 	BUILD_BUG_ON(sizeof(struct goldfish_pipe_command) > PAGE_SIZE);
717 	pipe->command_buffer =
718 		(struct goldfish_pipe_command *)__get_free_page(GFP_KERNEL);
719 	if (!pipe->command_buffer) {
720 		status = -ENOMEM;
721 		goto err_pipe;
722 	}
723 
724 	spin_lock_irqsave(&dev->lock, flags);
725 
726 	id = get_free_pipe_id_locked(dev);
727 	if (id < 0) {
728 		status = id;
729 		goto err_id_locked;
730 	}
731 
732 	dev->pipes[id] = pipe;
733 	pipe->id = id;
734 	pipe->command_buffer->id = id;
735 
736 	/* Now tell the emulator we're opening a new pipe. */
737 	dev->buffers->open_command_params.rw_params_max_count =
738 			MAX_BUFFERS_PER_COMMAND;
739 	dev->buffers->open_command_params.command_buffer_ptr =
740 			(u64)(unsigned long)__pa(pipe->command_buffer);
741 	status = goldfish_pipe_cmd_locked(pipe, PIPE_CMD_OPEN);
742 	spin_unlock_irqrestore(&dev->lock, flags);
743 	if (status < 0)
744 		goto err_cmd;
745 	/* All is done, save the pipe into the file's private data field */
746 	file->private_data = pipe;
747 	return 0;
748 
749 err_cmd:
750 	spin_lock_irqsave(&dev->lock, flags);
751 	dev->pipes[id] = NULL;
752 err_id_locked:
753 	spin_unlock_irqrestore(&dev->lock, flags);
754 	free_page((unsigned long)pipe->command_buffer);
755 err_pipe:
756 	kfree(pipe);
757 	return status;
758 }
759 
goldfish_pipe_release(struct inode * inode,struct file * filp)760 static int goldfish_pipe_release(struct inode *inode, struct file *filp)
761 {
762 	unsigned long flags;
763 	struct goldfish_pipe *pipe = filp->private_data;
764 	struct goldfish_pipe_dev *dev = pipe->dev;
765 
766 	/* The guest is closing the channel, so tell the emulator right now */
767 	goldfish_pipe_cmd(pipe, PIPE_CMD_CLOSE);
768 
769 	spin_lock_irqsave(&dev->lock, flags);
770 	dev->pipes[pipe->id] = NULL;
771 	signalled_pipes_remove_locked(dev, pipe);
772 	spin_unlock_irqrestore(&dev->lock, flags);
773 
774 	filp->private_data = NULL;
775 	free_page((unsigned long)pipe->command_buffer);
776 	kfree(pipe);
777 	return 0;
778 }
779 
780 static const struct file_operations goldfish_pipe_fops = {
781 	.owner = THIS_MODULE,
782 	.read = goldfish_pipe_read,
783 	.write = goldfish_pipe_write,
784 	.poll = goldfish_pipe_poll,
785 	.open = goldfish_pipe_open,
786 	.release = goldfish_pipe_release,
787 };
788 
init_miscdevice(struct miscdevice * miscdev)789 static void init_miscdevice(struct miscdevice *miscdev)
790 {
791 	memset(miscdev, 0, sizeof(*miscdev));
792 
793 	miscdev->minor = MISC_DYNAMIC_MINOR;
794 	miscdev->name = "goldfish_pipe";
795 	miscdev->fops = &goldfish_pipe_fops;
796 }
797 
write_pa_addr(void * addr,void __iomem * portl,void __iomem * porth)798 static void write_pa_addr(void *addr, void __iomem *portl, void __iomem *porth)
799 {
800 	const unsigned long paddr = __pa(addr);
801 
802 	writel(upper_32_bits(paddr), porth);
803 	writel(lower_32_bits(paddr), portl);
804 }
805 
goldfish_pipe_device_init(struct platform_device * pdev,struct goldfish_pipe_dev * dev)806 static int goldfish_pipe_device_init(struct platform_device *pdev,
807 				     struct goldfish_pipe_dev *dev)
808 {
809 	int err;
810 
811 	err = devm_request_threaded_irq(&pdev->dev, dev->irq,
812 					goldfish_pipe_interrupt,
813 					goldfish_interrupt_task,
814 					IRQF_SHARED, "goldfish_pipe", dev);
815 	if (err) {
816 		dev_err(&pdev->dev, "unable to allocate IRQ for v2\n");
817 		return err;
818 	}
819 
820 	init_miscdevice(&dev->miscdev);
821 	err = misc_register(&dev->miscdev);
822 	if (err) {
823 		dev_err(&pdev->dev, "unable to register v2 device\n");
824 		return err;
825 	}
826 
827 	dev->pdev_dev = &pdev->dev;
828 	dev->first_signalled_pipe = NULL;
829 	dev->pipes_capacity = INITIAL_PIPES_CAPACITY;
830 	dev->pipes = kcalloc(dev->pipes_capacity, sizeof(*dev->pipes),
831 			     GFP_KERNEL);
832 	if (!dev->pipes) {
833 		misc_deregister(&dev->miscdev);
834 		return -ENOMEM;
835 	}
836 
837 	/*
838 	 * We're going to pass two buffers, open_command_params and
839 	 * signalled_pipe_buffers, to the host. This means each of those buffers
840 	 * needs to be contained in a single physical page. The easiest choice
841 	 * is to just allocate a page and place the buffers in it.
842 	 */
843 	BUILD_BUG_ON(sizeof(struct goldfish_pipe_dev_buffers) > PAGE_SIZE);
844 	dev->buffers = (struct goldfish_pipe_dev_buffers *)
845 		__get_free_page(GFP_KERNEL);
846 	if (!dev->buffers) {
847 		kfree(dev->pipes);
848 		misc_deregister(&dev->miscdev);
849 		return -ENOMEM;
850 	}
851 
852 	/* Send the buffer addresses to the host */
853 	write_pa_addr(&dev->buffers->signalled_pipe_buffers,
854 		      dev->base + PIPE_REG_SIGNAL_BUFFER,
855 		      dev->base + PIPE_REG_SIGNAL_BUFFER_HIGH);
856 
857 	writel(MAX_SIGNALLED_PIPES,
858 	       dev->base + PIPE_REG_SIGNAL_BUFFER_COUNT);
859 
860 	write_pa_addr(&dev->buffers->open_command_params,
861 		      dev->base + PIPE_REG_OPEN_BUFFER,
862 		      dev->base + PIPE_REG_OPEN_BUFFER_HIGH);
863 
864 	platform_set_drvdata(pdev, dev);
865 	return 0;
866 }
867 
goldfish_pipe_device_deinit(struct platform_device * pdev,struct goldfish_pipe_dev * dev)868 static void goldfish_pipe_device_deinit(struct platform_device *pdev,
869 					struct goldfish_pipe_dev *dev)
870 {
871 	misc_deregister(&dev->miscdev);
872 	kfree(dev->pipes);
873 	free_page((unsigned long)dev->buffers);
874 }
875 
goldfish_pipe_probe(struct platform_device * pdev)876 static int goldfish_pipe_probe(struct platform_device *pdev)
877 {
878 	struct resource *r;
879 	struct goldfish_pipe_dev *dev;
880 
881 	dev = devm_kzalloc(&pdev->dev, sizeof(*dev), GFP_KERNEL);
882 	if (!dev)
883 		return -ENOMEM;
884 
885 	dev->magic = &goldfish_pipe_device_deinit;
886 	spin_lock_init(&dev->lock);
887 
888 	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
889 	if (!r || resource_size(r) < PAGE_SIZE) {
890 		dev_err(&pdev->dev, "can't allocate i/o page\n");
891 		return -EINVAL;
892 	}
893 	dev->base = devm_ioremap(&pdev->dev, r->start, PAGE_SIZE);
894 	if (!dev->base) {
895 		dev_err(&pdev->dev, "ioremap failed\n");
896 		return -EINVAL;
897 	}
898 
899 	dev->irq = platform_get_irq(pdev, 0);
900 	if (dev->irq < 0)
901 		return dev->irq;
902 
903 	/*
904 	 * Exchange the versions with the host device
905 	 *
906 	 * Note: v1 driver used to not report its version, so we write it before
907 	 *  reading device version back: this allows the host implementation to
908 	 *  detect the old driver (if there was no version write before read).
909 	 */
910 	writel(PIPE_DRIVER_VERSION, dev->base + PIPE_REG_VERSION);
911 	dev->version = readl(dev->base + PIPE_REG_VERSION);
912 	if (WARN_ON(dev->version < PIPE_CURRENT_DEVICE_VERSION))
913 		return -EINVAL;
914 
915 	return goldfish_pipe_device_init(pdev, dev);
916 }
917 
goldfish_pipe_remove(struct platform_device * pdev)918 static void goldfish_pipe_remove(struct platform_device *pdev)
919 {
920 	struct goldfish_pipe_dev *dev = platform_get_drvdata(pdev);
921 
922 	goldfish_pipe_device_deinit(pdev, dev);
923 }
924 
925 static const struct acpi_device_id goldfish_pipe_acpi_match[] = {
926 	{ "GFSH0003", 0 },
927 	{ },
928 };
929 MODULE_DEVICE_TABLE(acpi, goldfish_pipe_acpi_match);
930 
931 static const struct of_device_id goldfish_pipe_of_match[] = {
932 	{ .compatible = "google,android-pipe", },
933 	{},
934 };
935 MODULE_DEVICE_TABLE(of, goldfish_pipe_of_match);
936 
937 static struct platform_driver goldfish_pipe_driver = {
938 	.probe = goldfish_pipe_probe,
939 	.remove_new = goldfish_pipe_remove,
940 	.driver = {
941 		.name = "goldfish_pipe",
942 		.of_match_table = goldfish_pipe_of_match,
943 		.acpi_match_table = ACPI_PTR(goldfish_pipe_acpi_match),
944 	}
945 };
946 
947 module_platform_driver(goldfish_pipe_driver);
948 MODULE_AUTHOR("David Turner <digit@google.com>");
949 MODULE_DESCRIPTION("Goldfish virtual device for QEMU pipes");
950 MODULE_LICENSE("GPL v2");
951