staging: android: Delete the 'vsoc' driver

	  It is, in theory, a good memory allocator for low-memory devices,

	  because it can discard shared memory units when under memory pressure.

config ANDROID_VSOC

	tristate "Android Virtual SoC support"

	depends on PCI_MSI

	help

	  This option adds support for the Virtual SoC driver needed to boot

	  a 'cuttlefish' Android image inside QEmu. The driver interacts with

	  a QEmu ivshmem device. If built as a module, it will be called vsoc.

source "drivers/staging/android/ion/Kconfig"

endif # if ANDROID

obj-y					+= ion/

obj-$(CONFIG_ASHMEM)			+= ashmem.o

obj-$(CONFIG_ANDROID_VSOC)		+= vsoc.o

 - Split /dev/ion up into multiple nodes (e.g. /dev/ion/heap0)

 - Better test framework (integration with VGEM was suggested)

vsoc.c, uapi/vsoc_shm.h

 - The current driver uses the same wait queue for all of the futexes in a

   region. This will cause false wakeups in regions with a large number of

   waiting threads. We should eventually use multiple queues and select the

   queue based on the region.

 - Add debugfs support for examining the permissions of regions.

 - Remove VSOC_WAIT_FOR_INCOMING_INTERRUPT ioctl. This functionality has been

   superseded by the futex and is there for legacy reasons.

Please send patches to Greg Kroah-Hartman <greg@kroah.com> and Cc:

Arve Hjønnevåg <arve@android.com> and Riley Andrews <riandrews@android.com>

/* SPDX-License-Identifier: GPL-2.0 */

/*

 * Copyright (C) 2017 Google, Inc.

 *

 */

#ifndef _UAPI_LINUX_VSOC_SHM_H

#define _UAPI_LINUX_VSOC_SHM_H

#include <linux/types.h>

/**

 * A permission is a token that permits a receiver to read and/or write an area

 * of memory within a Vsoc region.

 *

 * An fd_scoped permission grants both read and write access, and can be

 * attached to a file description (see open(2)).

 * Ownership of the area can then be shared by passing a file descriptor

 * among processes.

 *

 * begin_offset and end_offset define the area of memory that is controlled by

 * the permission. owner_offset points to a word, also in shared memory, that

 * controls ownership of the area.

 *

 * ownership of the region expires when the associated file description is

 * released.

 *

 * At most one permission can be attached to each file description.

 *

 * This is useful when implementing HALs like gralloc that scope and pass

 * ownership of shared resources via file descriptors.

 *

 * The caller is responsibe for doing any fencing.

 *

 * The calling process will normally identify a currently free area of

 * memory. It will construct a proposed fd_scoped_permission_arg structure:

 *

 *   begin_offset and end_offset describe the area being claimed

 *

 *   owner_offset points to the location in shared memory that indicates the

 *   owner of the area.

 *

 *   owned_value is the value that will be stored in owner_offset iff the

 *   permission can be granted. It must be different than VSOC_REGION_FREE.

 *

 * Two fd_scoped_permission structures are compatible if they vary only by

 * their owned_value fields.

 *

 * The driver ensures that, for any group of simultaneous callers proposing

 * compatible fd_scoped_permissions, it will accept exactly one of the

 * propopsals. The other callers will get a failure with errno of EAGAIN.

 *

 * A process receiving a file descriptor can identify the region being

 * granted using the VSOC_GET_FD_SCOPED_PERMISSION ioctl.

 */

struct fd_scoped_permission {

	__u32 begin_offset;

	__u32 end_offset;

	__u32 owner_offset;

	__u32 owned_value;

};

/*

 * This value represents a free area of memory. The driver expects to see this

 * value at owner_offset when creating a permission otherwise it will not do it,

 * and will write this value back once the permission is no longer needed.

 */

#define VSOC_REGION_FREE ((__u32)0)

/**

 * ioctl argument for VSOC_CREATE_FD_SCOPE_PERMISSION

 */

struct fd_scoped_permission_arg {

	struct fd_scoped_permission perm;

	__s32 managed_region_fd;

};

#define VSOC_NODE_FREE ((__u32)0)

/*

 * Describes a signal table in shared memory. Each non-zero entry in the

 * table indicates that the receiver should signal the futex at the given

 * offset. Offsets are relative to the region, not the shared memory window.

 *

 * interrupt_signalled_offset is used to reliably signal interrupts across the

 * vmm boundary. There are two roles: transmitter and receiver. For example,

 * in the host_to_guest_signal_table the host is the transmitter and the

 * guest is the receiver. The protocol is as follows:

 *

 * 1. The transmitter should convert the offset of the futex to an offset

 *    in the signal table [0, (1 << num_nodes_lg2))

 *    The transmitter can choose any appropriate hashing algorithm, including

 *    hash = futex_offset & ((1 << num_nodes_lg2) - 1)

 *

 * 3. The transmitter should atomically compare and swap futex_offset with 0

 *    at hash. There are 3 possible outcomes

 *      a. The swap fails because the futex_offset is already in the table.

 *         The transmitter should stop.

 *      b. Some other offset is in the table. This is a hash collision. The

 *         transmitter should move to another table slot and try again. One

 *         possible algorithm:

 *         hash = (hash + 1) & ((1 << num_nodes_lg2) - 1)

 *      c. The swap worked. Continue below.

 *

 * 3. The transmitter atomically swaps 1 with the value at the

 *    interrupt_signalled_offset. There are two outcomes:

 *      a. The prior value was 1. In this case an interrupt has already been

 *         posted. The transmitter is done.

 *      b. The prior value was 0, indicating that the receiver may be sleeping.

 *         The transmitter will issue an interrupt.

 *

 * 4. On waking the receiver immediately exchanges a 0 with the

 *    interrupt_signalled_offset. If it receives a 0 then this a spurious

 *    interrupt. That may occasionally happen in the current protocol, but

 *    should be rare.

 *

 * 5. The receiver scans the signal table by atomicaly exchanging 0 at each

 *    location. If a non-zero offset is returned from the exchange the

 *    receiver wakes all sleepers at the given offset:

 *      futex((int*)(region_base + old_value), FUTEX_WAKE, MAX_INT);

 *

 * 6. The receiver thread then does a conditional wait, waking immediately

 *    if the value at interrupt_signalled_offset is non-zero. This catches cases

 *    here additional  signals were posted while the table was being scanned.

 *    On the guest the wait is handled via the VSOC_WAIT_FOR_INCOMING_INTERRUPT

 *    ioctl.

 */

struct vsoc_signal_table_layout {

	/* log_2(Number of signal table entries) */

	__u32 num_nodes_lg2;

	/*

	 * Offset to the first signal table entry relative to the start of the

	 * region

	 */

	__u32 futex_uaddr_table_offset;

	/*

	 * Offset to an atomic_t / atomic uint32_t. A non-zero value indicates

	 * that one or more offsets are currently posted in the table.

	 * semi-unique access to an entry in the table

	 */

	__u32 interrupt_signalled_offset;

};

#define VSOC_REGION_WHOLE ((__s32)0)

#define VSOC_DEVICE_NAME_SZ 16

/**

 * Each HAL would (usually) talk to a single device region

 * Mulitple entities care about these regions:

 * - The ivshmem_server will populate the regions in shared memory

 * - The guest kernel will read the region, create minor device nodes, and

 *   allow interested parties to register for FUTEX_WAKE events in the region

 * - HALs will access via the minor device nodes published by the guest kernel

 * - Host side processes will access the region via the ivshmem_server:

 *   1. Pass name to ivshmem_server at a UNIX socket

 *   2. ivshmemserver will reply with 2 fds:

 *     - host->guest doorbell fd

 *     - guest->host doorbell fd

 *     - fd for the shared memory region

 *     - region offset

 *   3. Start a futex receiver thread on the doorbell fd pointed at the

 *      signal_nodes

 */

struct vsoc_device_region {

	__u16 current_version;

	__u16 min_compatible_version;

	__u32 region_begin_offset;

	__u32 region_end_offset;

	__u32 offset_of_region_data;

	struct vsoc_signal_table_layout guest_to_host_signal_table;

	struct vsoc_signal_table_layout host_to_guest_signal_table;

	/* Name of the device. Must always be terminated with a '\0', so

	 * the longest supported device name is 15 characters.

	 */

	char device_name[VSOC_DEVICE_NAME_SZ];

	/* There are two ways that permissions to access regions are handled:

	 *   - When subdivided_by is VSOC_REGION_WHOLE, any process that can

	 *     open the device node for the region gains complete access to it.

	 *   - When subdivided is set processes that open the region cannot

	 *     access it. Access to a sub-region must be established by invoking

	 *     the VSOC_CREATE_FD_SCOPE_PERMISSION ioctl on the region

	 *     referenced in subdivided_by, providing a fileinstance

	 *     (represented by a fd) opened on this region.

	 */

	__u32 managed_by;

};

/*

 * The vsoc layout descriptor.

 * The first 4K should be reserved for the shm header and region descriptors.

 * The regions should be page aligned.

 */

struct vsoc_shm_layout_descriptor {

	__u16 major_version;

	__u16 minor_version;

	/* size of the shm. This may be redundant but nice to have */

	__u32 size;

	/* number of shared memory regions */

	__u32 region_count;

	/* The offset to the start of region descriptors */

	__u32 vsoc_region_desc_offset;

};

/*

 * This specifies the current version that should be stored in

 * vsoc_shm_layout_descriptor.major_version and

 * vsoc_shm_layout_descriptor.minor_version.

 * It should be updated only if the vsoc_device_region and

 * vsoc_shm_layout_descriptor structures have changed.

 * Versioning within each region is transferred

 * via the min_compatible_version and current_version fields in

 * vsoc_device_region. The driver does not consult these fields: they are left

 * for the HALs and host processes and will change independently of the layout

 * version.

 */

#define CURRENT_VSOC_LAYOUT_MAJOR_VERSION 2

#define CURRENT_VSOC_LAYOUT_MINOR_VERSION 0

#define VSOC_CREATE_FD_SCOPED_PERMISSION \

	_IOW(0xF5, 0, struct fd_scoped_permission)

#define VSOC_GET_FD_SCOPED_PERMISSION _IOR(0xF5, 1, struct fd_scoped_permission)

/*

 * This is used to signal the host to scan the guest_to_host_signal_table

 * for new futexes to wake. This sends an interrupt if one is not already

 * in flight.

 */

#define VSOC_MAYBE_SEND_INTERRUPT_TO_HOST _IO(0xF5, 2)

/*

 * When this returns the guest will scan host_to_guest_signal_table to

 * check for new futexes to wake.

 */

/* TODO(ghartman): Consider moving this to the bottom half */

#define VSOC_WAIT_FOR_INCOMING_INTERRUPT _IO(0xF5, 3)

/*

 * Guest HALs will use this to retrieve the region description after

 * opening their device node.

 */

#define VSOC_DESCRIBE_REGION _IOR(0xF5, 4, struct vsoc_device_region)

/*

 * Wake any threads that may be waiting for a host interrupt on this region.

 * This is mostly used during shutdown.

 */

#define VSOC_SELF_INTERRUPT _IO(0xF5, 5)

/*

 * This is used to signal the host to scan the guest_to_host_signal_table

 * for new futexes to wake. This sends an interrupt unconditionally.

 */

#define VSOC_SEND_INTERRUPT_TO_HOST _IO(0xF5, 6)

enum wait_types {

	VSOC_WAIT_UNDEFINED = 0,

	VSOC_WAIT_IF_EQUAL = 1,

	VSOC_WAIT_IF_EQUAL_TIMEOUT = 2

};

/*

 * Wait for a condition to be true

 *

 * Note, this is sized and aligned so the 32 bit and 64 bit layouts are

 * identical.

 */

struct vsoc_cond_wait {

	/* Input: Offset of the 32 bit word to check */

	__u32 offset;

	/* Input: Value that will be compared with the offset */

	__u32 value;

	/* Monotonic time to wake at in seconds */

	__u64 wake_time_sec;

	/* Input: Monotonic time to wait in nanoseconds */

	__u32 wake_time_nsec;

	/* Input: Type of wait */

	__u32 wait_type;

	/* Output: Number of times the thread woke before returning. */

	__u32 wakes;

	/* Ensure that we're 8-byte aligned and 8 byte length for 32/64 bit

	 * compatibility.

	 */

	__u32 reserved_1;

};

#define VSOC_COND_WAIT _IOWR(0xF5, 7, struct vsoc_cond_wait)

/* Wake any local threads waiting at the offset given in arg */

#define VSOC_COND_WAKE _IO(0xF5, 8)

#endif /* _UAPI_LINUX_VSOC_SHM_H */