[v13,06/24] gunyah: rsc_mgr: Add resource manager RPC core

  The resource manager is a special virtual machine which is always
running on a Gunyah system. It provides APIs for creating and destroying
VMs, secure memory management, sharing/lending of memory between VMs,
and setup of inter-VM communication. Calls to the resource manager are
made via message queues.

This patch implements the basic probing and RPC mechanism to make those
API calls. Request/response calls can be made with gh_rm_call.
Drivers can also register to notifications pushed by RM via
gh_rm_register_notifier

Specific API calls that resource manager supports will be implemented in
subsequent patches.

Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
---
 drivers/virt/Makefile          |   1 +
 drivers/virt/gunyah/Makefile   |   4 +
 drivers/virt/gunyah/rsc_mgr.c  | 702 +++++++++++++++++++++++++++++++++
 drivers/virt/gunyah/rsc_mgr.h  |  16 +
 include/linux/gunyah_rsc_mgr.h |  21 +
 5 files changed, 744 insertions(+)
 create mode 100644 drivers/virt/gunyah/Makefile
 create mode 100644 drivers/virt/gunyah/rsc_mgr.c
 create mode 100644 drivers/virt/gunyah/rsc_mgr.h
 create mode 100644 include/linux/gunyah_rsc_mgr.h
  

On 5/9/23 3:47 PM, Elliot Berman wrote:
> The resource manager is a special virtual machine which is always
> running on a Gunyah system. It provides APIs for creating and destroying
> VMs, secure memory management, sharing/lending of memory between VMs,
> and setup of inter-VM communication. Calls to the resource manager are
> made via message queues.
> 
> This patch implements the basic probing and RPC mechanism to make those
> API calls. Request/response calls can be made with gh_rm_call.
> Drivers can also register to notifications pushed by RM via
> gh_rm_register_notifier
> 
> Specific API calls that resource manager supports will be implemented in
> subsequent patches.
> 
> Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>

I have some comments below, but none is critical so whether or not you
address what I mention:

Reviewed-by: Alex Elder <elder@linaro.org>

> ---
>   drivers/virt/Makefile          |   1 +
>   drivers/virt/gunyah/Makefile   |   4 +
>   drivers/virt/gunyah/rsc_mgr.c  | 702 +++++++++++++++++++++++++++++++++
>   drivers/virt/gunyah/rsc_mgr.h  |  16 +
>   include/linux/gunyah_rsc_mgr.h |  21 +
>   5 files changed, 744 insertions(+)
>   create mode 100644 drivers/virt/gunyah/Makefile
>   create mode 100644 drivers/virt/gunyah/rsc_mgr.c
>   create mode 100644 drivers/virt/gunyah/rsc_mgr.h
>   create mode 100644 include/linux/gunyah_rsc_mgr.h
> 
> diff --git a/drivers/virt/Makefile b/drivers/virt/Makefile
> index e9aa6fc96fab..a5817e2d7d71 100644
> --- a/drivers/virt/Makefile
> +++ b/drivers/virt/Makefile
> @@ -12,3 +12,4 @@ obj-$(CONFIG_ACRN_HSM)		+= acrn/
>   obj-$(CONFIG_EFI_SECRET)	+= coco/efi_secret/
>   obj-$(CONFIG_SEV_GUEST)		+= coco/sev-guest/
>   obj-$(CONFIG_INTEL_TDX_GUEST)	+= coco/tdx-guest/
> +obj-y				+= gunyah/
> diff --git a/drivers/virt/gunyah/Makefile b/drivers/virt/gunyah/Makefile
> new file mode 100644
> index 000000000000..0f5aec834698
> --- /dev/null
> +++ b/drivers/virt/gunyah/Makefile
> @@ -0,0 +1,4 @@
> +# SPDX-License-Identifier: GPL-2.0
> +
> +gunyah-y += rsc_mgr.o
> +obj-$(CONFIG_GUNYAH) += gunyah.o
> diff --git a/drivers/virt/gunyah/rsc_mgr.c b/drivers/virt/gunyah/rsc_mgr.c
> new file mode 100644
> index 000000000000..88b5beb1ea51
> --- /dev/null
> +++ b/drivers/virt/gunyah/rsc_mgr.c
> @@ -0,0 +1,702 @@

. . .

> +/**
> + * struct gh_rm - private data for communicating w/Gunyah resource manager
> + * @dev: pointer to device

This points to the device structure for the RM platform device.
(Maybe that's clear...)

> + * @tx_ghrsc: message queue resource to TX to RM
> + * @rx_ghrsc: message queue resource to RX from RM
> + * @msgq: mailbox instance of TX/RX resources above
> + * @msgq_client: mailbox client of above msgq
> + * @active_rx_connection: ongoing gh_rm_connection for which we're receiving fragments
> + * @last_tx_ret: return value of last mailbox tx
> + * @call_xarray: xarray to allocate & lookup sequence IDs for Request/Response flows
> + * @next_seq: next ID to allocate (for xa_alloc_cyclic)
> + * @cache: cache for allocating Tx messages
> + * @send_lock: synchronization to allow only one request to be sent at a time
> + * @nh: notifier chain for clients interested in RM notification messages
> + */
> +struct gh_rm {
> +	struct device *dev;
> +	struct gh_resource tx_ghrsc;
> +	struct gh_resource rx_ghrsc;
> +	struct gh_msgq msgq;
> +	struct mbox_client msgq_client;
> +	struct gh_rm_connection *active_rx_connection;
> +	int last_tx_ret;
> +
> +	struct xarray call_xarray;
> +	u32 next_seq;
> +
> +	struct kmem_cache *cache;
> +	struct mutex send_lock;
> +	struct blocking_notifier_head nh;
> +};
> +
> +/**
> + * gh_rm_remap_error() - Remap Gunyah resource manager errors into a Linux error code
> + * @rm_error: "Standard" return value from Gunyah resource manager
> + */
> +static inline int gh_rm_remap_error(enum gh_rm_error rm_error)

I suggested something similar last time.  I you are operating
on an rm_error value, so I would call this gh_rm_error_remap().

> +{
> +	switch (rm_error) {
> +	case GH_RM_ERROR_OK:
> +		return 0;
> +	case GH_RM_ERROR_UNIMPLEMENTED:
> +		return -EOPNOTSUPP;
> +	case GH_RM_ERROR_NOMEM:
> +		return -ENOMEM;
> +	case GH_RM_ERROR_NORESOURCE:
> +		return -ENODEV;
> +	case GH_RM_ERROR_DENIED:
> +		return -EPERM;
> +	case GH_RM_ERROR_BUSY:
> +		return -EBUSY;
> +	case GH_RM_ERROR_INVALID:
> +	case GH_RM_ERROR_ARGUMENT_INVALID:
> +	case GH_RM_ERROR_HANDLE_INVALID:
> +	case GH_RM_ERROR_VALIDATE_FAILED:
> +	case GH_RM_ERROR_MAP_FAILED:
> +	case GH_RM_ERROR_MEM_INVALID:
> +	case GH_RM_ERROR_MEM_INUSE:
> +	case GH_RM_ERROR_MEM_RELEASED:
> +	case GH_RM_ERROR_VMID_INVALID:
> +	case GH_RM_ERROR_LOOKUP_FAILED:
> +	case GH_RM_ERROR_IRQ_INVALID:
> +	case GH_RM_ERROR_IRQ_INUSE:
> +	case GH_RM_ERROR_IRQ_RELEASED:
> +		return -EINVAL;
> +	default:
> +		return -EBADMSG;
> +	}
> +}

. . .

> +static void gh_rm_process_rply(struct gh_rm *rm, void *msg, size_t msg_size)
> +{
> +	struct gh_rm_rpc_reply_hdr *reply_hdr = msg;
> +	struct gh_rm_connection *connection;
> +	u16 seq_id;
> +
> +	seq_id = le16_to_cpu(reply_hdr->hdr.seq);
> +	connection = xa_load(&rm->call_xarray, seq_id);
> +
> +	if (!connection || connection->msg_id != reply_hdr->hdr.msg_id)
> +		return;

Do either of the above conditions warrant reporting a warning if
it occurs?  Or are these expected to be possible--and if either
occur they're harmless if handled this way?

> +
> +	if (rm->active_rx_connection)
> +		gh_rm_abort_connection(rm);
> +
> +	if (gh_rm_init_connection_payload(connection, msg, sizeof(*reply_hdr), msg_size)) {
> +		dev_err(rm->dev, "Failed to alloc connection buffer for sequence %d\n", seq_id);
> +		/* Send connection complete and error the client. */
> +		connection->reply.ret = -ENOMEM;
> +		complete(&connection->reply.seq_done);
> +		return;
> +	}
> +
> +	connection->reply.rm_error = le32_to_cpu(reply_hdr->err_code);
> +	rm->active_rx_connection = connection;
> +}

. . .
  

On 09/05/2023 21:47, Elliot Berman wrote:
> The resource manager is a special virtual machine which is always
> running on a Gunyah system. It provides APIs for creating and destroying
> VMs, secure memory management, sharing/lending of memory between VMs,
> and setup of inter-VM communication. Calls to the resource manager are
> made via message queues.
> 
> This patch implements the basic probing and RPC mechanism to make those
> API calls. Request/response calls can be made with gh_rm_call.
> Drivers can also register to notifications pushed by RM via
> gh_rm_register_notifier
> 
> Specific API calls that resource manager supports will be implemented in
> subsequent patches.
> 
> Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
> ---

Reviewed-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>

--srini

>   drivers/virt/Makefile          |   1 +
>   drivers/virt/gunyah/Makefile   |   4 +
>   drivers/virt/gunyah/rsc_mgr.c  | 702 +++++++++++++++++++++++++++++++++
>   drivers/virt/gunyah/rsc_mgr.h  |  16 +
>   include/linux/gunyah_rsc_mgr.h |  21 +
>   5 files changed, 744 insertions(+)
>   create mode 100644 drivers/virt/gunyah/Makefile
>   create mode 100644 drivers/virt/gunyah/rsc_mgr.c
>   create mode 100644 drivers/virt/gunyah/rsc_mgr.h
>   create mode 100644 include/linux/gunyah_rsc_mgr.h
> 
> diff --git a/drivers/virt/Makefile b/drivers/virt/Makefile
> index e9aa6fc96fab..a5817e2d7d71 100644
> --- a/drivers/virt/Makefile
> +++ b/drivers/virt/Makefile
> @@ -12,3 +12,4 @@ obj-$(CONFIG_ACRN_HSM)		+= acrn/
>   obj-$(CONFIG_EFI_SECRET)	+= coco/efi_secret/
>   obj-$(CONFIG_SEV_GUEST)		+= coco/sev-guest/
>   obj-$(CONFIG_INTEL_TDX_GUEST)	+= coco/tdx-guest/
> +obj-y				+= gunyah/
> diff --git a/drivers/virt/gunyah/Makefile b/drivers/virt/gunyah/Makefile
> new file mode 100644
> index 000000000000..0f5aec834698
> --- /dev/null
> +++ b/drivers/virt/gunyah/Makefile
> @@ -0,0 +1,4 @@
> +# SPDX-License-Identifier: GPL-2.0
> +
> +gunyah-y += rsc_mgr.o
> +obj-$(CONFIG_GUNYAH) += gunyah.o
> diff --git a/drivers/virt/gunyah/rsc_mgr.c b/drivers/virt/gunyah/rsc_mgr.c
> new file mode 100644
> index 000000000000..88b5beb1ea51
> --- /dev/null
> +++ b/drivers/virt/gunyah/rsc_mgr.c
> @@ -0,0 +1,702 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2022-2023 Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +
> +#include <linux/of.h>
> +#include <linux/slab.h>
> +#include <linux/mutex.h>
> +#include <linux/sched.h>
> +#include <linux/gunyah.h>
> +#include <linux/module.h>
> +#include <linux/of_irq.h>
> +#include <linux/notifier.h>
> +#include <linux/workqueue.h>
> +#include <linux/completion.h>
> +#include <linux/gunyah_rsc_mgr.h>
> +#include <linux/platform_device.h>
> +
> +#include "rsc_mgr.h"
> +
> +#define RM_RPC_API_VERSION_MASK		GENMASK(3, 0)
> +#define RM_RPC_HEADER_WORDS_MASK	GENMASK(7, 4)
> +#define RM_RPC_API_VERSION		FIELD_PREP(RM_RPC_API_VERSION_MASK, 1)
> +#define RM_RPC_HEADER_WORDS		FIELD_PREP(RM_RPC_HEADER_WORDS_MASK, \
> +						(sizeof(struct gh_rm_rpc_hdr) / sizeof(u32)))
> +#define RM_RPC_API			(RM_RPC_API_VERSION | RM_RPC_HEADER_WORDS)
> +
> +#define RM_RPC_TYPE_CONTINUATION	0x0
> +#define RM_RPC_TYPE_REQUEST		0x1
> +#define RM_RPC_TYPE_REPLY		0x2
> +#define RM_RPC_TYPE_NOTIF		0x3
> +#define RM_RPC_TYPE_MASK		GENMASK(1, 0)
> +
> +#define GH_RM_MAX_NUM_FRAGMENTS		62
> +#define RM_RPC_FRAGMENTS_MASK		GENMASK(7, 2)
> +
> +struct gh_rm_rpc_hdr {
> +	u8 api;
> +	u8 type;
> +	__le16 seq;
> +	__le32 msg_id;
> +} __packed;
> +
> +struct gh_rm_rpc_reply_hdr {
> +	struct gh_rm_rpc_hdr hdr;
> +	__le32 err_code; /* GH_RM_ERROR_* */
> +} __packed;
> +
> +#define GH_RM_MAX_MSG_SIZE	(GH_MSGQ_MAX_MSG_SIZE - sizeof(struct gh_rm_rpc_hdr))
> +
> +/* RM Error codes */
> +enum gh_rm_error {
> +	GH_RM_ERROR_OK			= 0x0,
> +	GH_RM_ERROR_UNIMPLEMENTED	= 0xFFFFFFFF,
> +	GH_RM_ERROR_NOMEM		= 0x1,
> +	GH_RM_ERROR_NORESOURCE		= 0x2,
> +	GH_RM_ERROR_DENIED		= 0x3,
> +	GH_RM_ERROR_INVALID		= 0x4,
> +	GH_RM_ERROR_BUSY		= 0x5,
> +	GH_RM_ERROR_ARGUMENT_INVALID	= 0x6,
> +	GH_RM_ERROR_HANDLE_INVALID	= 0x7,
> +	GH_RM_ERROR_VALIDATE_FAILED	= 0x8,
> +	GH_RM_ERROR_MAP_FAILED		= 0x9,
> +	GH_RM_ERROR_MEM_INVALID		= 0xA,
> +	GH_RM_ERROR_MEM_INUSE		= 0xB,
> +	GH_RM_ERROR_MEM_RELEASED	= 0xC,
> +	GH_RM_ERROR_VMID_INVALID	= 0xD,
> +	GH_RM_ERROR_LOOKUP_FAILED	= 0xE,
> +	GH_RM_ERROR_IRQ_INVALID		= 0xF,
> +	GH_RM_ERROR_IRQ_INUSE		= 0x10,
> +	GH_RM_ERROR_IRQ_RELEASED	= 0x11,
> +};
> +
> +/**
> + * struct gh_rm_connection - Represents a complete message from resource manager
> + * @payload: Combined payload of all the fragments (msg headers stripped off).
> + * @size: Size of the payload received so far.
> + * @msg_id: Message ID from the header.
> + * @type: RM_RPC_TYPE_REPLY or RM_RPC_TYPE_NOTIF.
> + * @num_fragments: total number of fragments expected to be received.
> + * @fragments_received: fragments received so far.
> + * @reply: Fields used for request/reply sequences
> + * @notification: Fields used for notifiations
> + */
> +struct gh_rm_connection {
> +	void *payload;
> +	size_t size;
> +	__le32 msg_id;
> +	u8 type;
> +
> +	u8 num_fragments;
> +	u8 fragments_received;
> +
> +	union {
> +		/**
> +		 * @ret: Linux return code, there was an error processing connection
> +		 * @seq: Sequence ID for the main message.
> +		 * @rm_error: For request/reply sequences with standard replies
> +		 * @seq_done: Signals caller that the RM reply has been received
> +		 */
> +		struct {
> +			int ret;
> +			u16 seq;
> +			enum gh_rm_error rm_error;
> +			struct completion seq_done;
> +		} reply;
> +
> +		/**
> +		 * @rm: Pointer to the RM that launched the connection
> +		 * @work: Triggered when all fragments of a notification received
> +		 */
> +		struct {
> +			struct gh_rm *rm;
> +			struct work_struct work;
> +		} notification;
> +	};
> +};
> +
> +/**
> + * struct gh_rm - private data for communicating w/Gunyah resource manager
> + * @dev: pointer to device
> + * @tx_ghrsc: message queue resource to TX to RM
> + * @rx_ghrsc: message queue resource to RX from RM
> + * @msgq: mailbox instance of TX/RX resources above
> + * @msgq_client: mailbox client of above msgq
> + * @active_rx_connection: ongoing gh_rm_connection for which we're receiving fragments
> + * @last_tx_ret: return value of last mailbox tx
> + * @call_xarray: xarray to allocate & lookup sequence IDs for Request/Response flows
> + * @next_seq: next ID to allocate (for xa_alloc_cyclic)
> + * @cache: cache for allocating Tx messages
> + * @send_lock: synchronization to allow only one request to be sent at a time
> + * @nh: notifier chain for clients interested in RM notification messages
> + */
> +struct gh_rm {
> +	struct device *dev;
> +	struct gh_resource tx_ghrsc;
> +	struct gh_resource rx_ghrsc;
> +	struct gh_msgq msgq;
> +	struct mbox_client msgq_client;
> +	struct gh_rm_connection *active_rx_connection;
> +	int last_tx_ret;
> +
> +	struct xarray call_xarray;
> +	u32 next_seq;
> +
> +	struct kmem_cache *cache;
> +	struct mutex send_lock;
> +	struct blocking_notifier_head nh;
> +};
> +
> +/**
> + * gh_rm_remap_error() - Remap Gunyah resource manager errors into a Linux error code
> + * @rm_error: "Standard" return value from Gunyah resource manager
> + */
> +static inline int gh_rm_remap_error(enum gh_rm_error rm_error)
> +{
> +	switch (rm_error) {
> +	case GH_RM_ERROR_OK:
> +		return 0;
> +	case GH_RM_ERROR_UNIMPLEMENTED:
> +		return -EOPNOTSUPP;
> +	case GH_RM_ERROR_NOMEM:
> +		return -ENOMEM;
> +	case GH_RM_ERROR_NORESOURCE:
> +		return -ENODEV;
> +	case GH_RM_ERROR_DENIED:
> +		return -EPERM;
> +	case GH_RM_ERROR_BUSY:
> +		return -EBUSY;
> +	case GH_RM_ERROR_INVALID:
> +	case GH_RM_ERROR_ARGUMENT_INVALID:
> +	case GH_RM_ERROR_HANDLE_INVALID:
> +	case GH_RM_ERROR_VALIDATE_FAILED:
> +	case GH_RM_ERROR_MAP_FAILED:
> +	case GH_RM_ERROR_MEM_INVALID:
> +	case GH_RM_ERROR_MEM_INUSE:
> +	case GH_RM_ERROR_MEM_RELEASED:
> +	case GH_RM_ERROR_VMID_INVALID:
> +	case GH_RM_ERROR_LOOKUP_FAILED:
> +	case GH_RM_ERROR_IRQ_INVALID:
> +	case GH_RM_ERROR_IRQ_INUSE:
> +	case GH_RM_ERROR_IRQ_RELEASED:
> +		return -EINVAL;
> +	default:
> +		return -EBADMSG;
> +	}
> +}
> +
> +static int gh_rm_init_connection_payload(struct gh_rm_connection *connection, void *msg,
> +					size_t hdr_size, size_t msg_size)
> +{
> +	size_t max_buf_size, payload_size;
> +	struct gh_rm_rpc_hdr *hdr = msg;
> +
> +	if (msg_size < hdr_size)
> +		return -EINVAL;
> +
> +	payload_size = msg_size - hdr_size;
> +
> +	connection->num_fragments = FIELD_GET(RM_RPC_FRAGMENTS_MASK, hdr->type);
> +	connection->fragments_received = 0;
> +
> +	/* There's not going to be any payload, no need to allocate buffer. */
> +	if (!payload_size && !connection->num_fragments)
> +		return 0;
> +
> +	if (connection->num_fragments > GH_RM_MAX_NUM_FRAGMENTS)
> +		return -EINVAL;
> +
> +	max_buf_size = payload_size + (connection->num_fragments * GH_RM_MAX_MSG_SIZE);
> +
> +	connection->payload = kzalloc(max_buf_size, GFP_KERNEL);
> +	if (!connection->payload)
> +		return -ENOMEM;
> +
> +	memcpy(connection->payload, msg + hdr_size, payload_size);
> +	connection->size = payload_size;
> +	return 0;
> +}
> +
> +static void gh_rm_abort_connection(struct gh_rm *rm)
> +{
> +	switch (rm->active_rx_connection->type) {
> +	case RM_RPC_TYPE_REPLY:
> +		rm->active_rx_connection->reply.ret = -EIO;
> +		complete(&rm->active_rx_connection->reply.seq_done);
> +		break;
> +	case RM_RPC_TYPE_NOTIF:
> +		fallthrough;
> +	default:
> +		kfree(rm->active_rx_connection->payload);
> +		kfree(rm->active_rx_connection);
> +	}
> +
> +	rm->active_rx_connection = NULL;
> +}
> +
> +static void gh_rm_notif_work(struct work_struct *work)
> +{
> +	struct gh_rm_connection *connection = container_of(work, struct gh_rm_connection,
> +								notification.work);
> +	struct gh_rm *rm = connection->notification.rm;
> +
> +	blocking_notifier_call_chain(&rm->nh, le32_to_cpu(connection->msg_id), connection->payload);
> +
> +	put_device(rm->dev);
> +	kfree(connection->payload);
> +	kfree(connection);
> +}
> +
> +static void gh_rm_process_notif(struct gh_rm *rm, void *msg, size_t msg_size)
> +{
> +	struct gh_rm_connection *connection;
> +	struct gh_rm_rpc_hdr *hdr = msg;
> +	int ret;
> +
> +	if (rm->active_rx_connection)
> +		gh_rm_abort_connection(rm);
> +
> +	connection = kzalloc(sizeof(*connection), GFP_KERNEL);
> +	if (!connection)
> +		return;
> +
> +	connection->type = RM_RPC_TYPE_NOTIF;
> +	connection->msg_id = hdr->msg_id;
> +
> +	get_device(rm->dev);
> +	connection->notification.rm = rm;
> +	INIT_WORK(&connection->notification.work, gh_rm_notif_work);
> +
> +	ret = gh_rm_init_connection_payload(connection, msg, sizeof(*hdr), msg_size);
> +	if (ret) {
> +		dev_err(rm->dev, "Failed to initialize connection for notification: %d\n", ret);
> +		put_device(rm->dev);
> +		kfree(connection);
> +		return;
> +	}
> +
> +	rm->active_rx_connection = connection;
> +}
> +
> +static void gh_rm_process_rply(struct gh_rm *rm, void *msg, size_t msg_size)
> +{
> +	struct gh_rm_rpc_reply_hdr *reply_hdr = msg;
> +	struct gh_rm_connection *connection;
> +	u16 seq_id;
> +
> +	seq_id = le16_to_cpu(reply_hdr->hdr.seq);
> +	connection = xa_load(&rm->call_xarray, seq_id);
> +
> +	if (!connection || connection->msg_id != reply_hdr->hdr.msg_id)
> +		return;
> +
> +	if (rm->active_rx_connection)
> +		gh_rm_abort_connection(rm);
> +
> +	if (gh_rm_init_connection_payload(connection, msg, sizeof(*reply_hdr), msg_size)) {
> +		dev_err(rm->dev, "Failed to alloc connection buffer for sequence %d\n", seq_id);
> +		/* Send connection complete and error the client. */
> +		connection->reply.ret = -ENOMEM;
> +		complete(&connection->reply.seq_done);
> +		return;
> +	}
> +
> +	connection->reply.rm_error = le32_to_cpu(reply_hdr->err_code);
> +	rm->active_rx_connection = connection;
> +}
> +
> +static void gh_rm_process_cont(struct gh_rm *rm, struct gh_rm_connection *connection,
> +				void *msg, size_t msg_size)
> +{
> +	struct gh_rm_rpc_hdr *hdr = msg;
> +	size_t payload_size = msg_size - sizeof(*hdr);
> +
> +	if (!rm->active_rx_connection)
> +		return;
> +
> +	/*
> +	 * hdr->fragments and hdr->msg_id preserves the value from first reply
> +	 * or notif message. To detect mishandling, check it's still intact.
> +	 */
> +	if (connection->msg_id != hdr->msg_id ||
> +		connection->num_fragments != FIELD_GET(RM_RPC_FRAGMENTS_MASK, hdr->type)) {
> +		gh_rm_abort_connection(rm);
> +		return;
> +	}
> +
> +	memcpy(connection->payload + connection->size, msg + sizeof(*hdr), payload_size);
> +	connection->size += payload_size;
> +	connection->fragments_received++;
> +}
> +
> +static void gh_rm_try_complete_connection(struct gh_rm *rm)
> +{
> +	struct gh_rm_connection *connection = rm->active_rx_connection;
> +
> +	if (!connection || connection->fragments_received != connection->num_fragments)
> +		return;
> +
> +	switch (connection->type) {
> +	case RM_RPC_TYPE_REPLY:
> +		complete(&connection->reply.seq_done);
> +		break;
> +	case RM_RPC_TYPE_NOTIF:
> +		schedule_work(&connection->notification.work);
> +		break;
> +	default:
> +		dev_err_ratelimited(rm->dev, "Invalid message type (%u) received\n",
> +					connection->type);
> +		gh_rm_abort_connection(rm);
> +		break;
> +	}
> +
> +	rm->active_rx_connection = NULL;
> +}
> +
> +static void gh_rm_msgq_rx_data(struct mbox_client *cl, void *mssg)
> +{
> +	struct gh_rm *rm = container_of(cl, struct gh_rm, msgq_client);
> +	struct gh_msgq_rx_data *rx_data = mssg;
> +	size_t msg_size = rx_data->length;
> +	void *msg = rx_data->data;
> +	struct gh_rm_rpc_hdr *hdr;
> +
> +	if (msg_size < sizeof(*hdr) || msg_size > GH_MSGQ_MAX_MSG_SIZE)
> +		return;
> +
> +	hdr = msg;
> +	if (hdr->api != RM_RPC_API) {
> +		dev_err(rm->dev, "Unknown RM RPC API version: %x\n", hdr->api);
> +		return;
> +	}
> +
> +	switch (FIELD_GET(RM_RPC_TYPE_MASK, hdr->type)) {
> +	case RM_RPC_TYPE_NOTIF:
> +		gh_rm_process_notif(rm, msg, msg_size);
> +		break;
> +	case RM_RPC_TYPE_REPLY:
> +		gh_rm_process_rply(rm, msg, msg_size);
> +		break;
> +	case RM_RPC_TYPE_CONTINUATION:
> +		gh_rm_process_cont(rm, rm->active_rx_connection, msg, msg_size);
> +		break;
> +	default:
> +		dev_err(rm->dev, "Invalid message type (%lu) received\n",
> +			FIELD_GET(RM_RPC_TYPE_MASK, hdr->type));
> +		return;
> +	}
> +
> +	gh_rm_try_complete_connection(rm);
> +}
> +
> +static void gh_rm_msgq_tx_done(struct mbox_client *cl, void *mssg, int r)
> +{
> +	struct gh_rm *rm = container_of(cl, struct gh_rm, msgq_client);
> +
> +	kmem_cache_free(rm->cache, mssg);
> +	rm->last_tx_ret = r;
> +}
> +
> +static int gh_rm_send_request(struct gh_rm *rm, u32 message_id,
> +			      const void *req_buf, size_t req_buf_size,
> +			      struct gh_rm_connection *connection)
> +{
> +	size_t buf_size_remaining = req_buf_size;
> +	const void *req_buf_curr = req_buf;
> +	struct gh_msgq_tx_data *msg;
> +	struct gh_rm_rpc_hdr *hdr, hdr_template;
> +	u32 cont_fragments = 0;
> +	size_t payload_size;
> +	void *payload;
> +	int ret;
> +
> +	if (req_buf_size > GH_RM_MAX_NUM_FRAGMENTS * GH_RM_MAX_MSG_SIZE) {
> +		dev_warn(rm->dev, "Limit (%lu bytes) exceeded for the maximum message size: %lu\n",
> +			GH_RM_MAX_NUM_FRAGMENTS * GH_RM_MAX_MSG_SIZE, req_buf_size);
> +		dump_stack();
> +		return -E2BIG;
> +	}
> +
> +	if (req_buf_size)
> +		cont_fragments = (req_buf_size - 1) / GH_RM_MAX_MSG_SIZE;
> +
> +	hdr_template.api = RM_RPC_API;
> +	hdr_template.type = FIELD_PREP(RM_RPC_TYPE_MASK, RM_RPC_TYPE_REQUEST) |
> +				FIELD_PREP(RM_RPC_FRAGMENTS_MASK, cont_fragments);
> +	hdr_template.seq = cpu_to_le16(connection->reply.seq);
> +	hdr_template.msg_id = cpu_to_le32(message_id);
> +
> +	ret = mutex_lock_interruptible(&rm->send_lock);
> +	if (ret)
> +		return ret;
> +
> +	do {
> +		msg = kmem_cache_zalloc(rm->cache, GFP_KERNEL);
> +		if (!msg) {
> +			ret = -ENOMEM;
> +			goto out;
> +		}
> +
> +		/* Fill header */
> +		hdr = (struct gh_rm_rpc_hdr *)&msg->data[0];
> +		*hdr = hdr_template;
> +
> +		/* Copy payload */
> +		payload = &msg->data[0] + sizeof(*hdr);
> +		payload_size = min(buf_size_remaining, GH_RM_MAX_MSG_SIZE);
> +		memcpy(payload, req_buf_curr, payload_size);
> +		req_buf_curr += payload_size;
> +		buf_size_remaining -= payload_size;
> +
> +		/* Force the last fragment to immediately alert the receiver */
> +		msg->push = !buf_size_remaining;
> +		msg->length = sizeof(*hdr) + payload_size;
> +
> +		ret = mbox_send_message(gh_msgq_chan(&rm->msgq), msg);
> +		if (ret < 0) {
> +			kmem_cache_free(rm->cache, msg);
> +			break;
> +		}
> +
> +		if (rm->last_tx_ret) {
> +			ret = rm->last_tx_ret;
> +			break;
> +		}
> +
> +		hdr_template.type = FIELD_PREP(RM_RPC_TYPE_MASK, RM_RPC_TYPE_CONTINUATION) |
> +					FIELD_PREP(RM_RPC_FRAGMENTS_MASK, cont_fragments);
> +	} while (buf_size_remaining);
> +
> +out:
> +	mutex_unlock(&rm->send_lock);
> +	return ret < 0 ? ret : 0;
> +}
> +
> +/**
> + * gh_rm_call: Achieve request-response type communication with RPC
> + * @rm: Pointer to Gunyah resource manager internal data
> + * @message_id: The RM RPC message-id
> + * @req_buf: Request buffer that contains the payload
> + * @req_buf_size: Total size of the payload
> + * @resp_buf: Pointer to a response buffer
> + * @resp_buf_size: Size of the response buffer
> + *
> + * Make a request to the Resource Manager and wait for reply back. For a successful
> + * response, the function returns the payload. The size of the payload is set in
> + * resp_buf_size. The resp_buf must be freed by the caller when 0 is returned
> + * and resp_buf_size != 0.
> + *
> + * req_buf should be not NULL for req_buf_size >0. If req_buf_size == 0,
> + * req_buf *can* be NULL and no additional payload is sent.
> + *
> + * Context: Process context. Will sleep waiting for reply.
> + * Return: 0 on success. <0 if error.
> + */
> +int gh_rm_call(struct gh_rm *rm, u32 message_id, const void *req_buf, size_t req_buf_size,
> +		void **resp_buf, size_t *resp_buf_size)
> +{
> +	struct gh_rm_connection *connection;
> +	u32 seq_id;
> +	int ret;
> +
> +	/* message_id 0 is reserved. req_buf_size implies req_buf is not NULL */
> +	if (!rm || !message_id || (!req_buf && req_buf_size))
> +		return -EINVAL;
> +
> +
> +	connection = kzalloc(sizeof(*connection), GFP_KERNEL);
> +	if (!connection)
> +		return -ENOMEM;
> +
> +	connection->type = RM_RPC_TYPE_REPLY;
> +	connection->msg_id = cpu_to_le32(message_id);
> +
> +	init_completion(&connection->reply.seq_done);
> +
> +	/* Allocate a new seq number for this connection */
> +	ret = xa_alloc_cyclic(&rm->call_xarray, &seq_id, connection, xa_limit_16b, &rm->next_seq,
> +				GFP_KERNEL);
> +	if (ret < 0)
> +		goto free;
> +	connection->reply.seq = lower_16_bits(seq_id);
> +
> +	/* Send the request to the Resource Manager */
> +	ret = gh_rm_send_request(rm, message_id, req_buf, req_buf_size, connection);
> +	if (ret < 0)
> +		goto out;
> +
> +	/* Wait for response */
> +	ret = wait_for_completion_interruptible(&connection->reply.seq_done);
> +	if (ret)
> +		goto out;
> +
> +	/* Check for internal (kernel) error waiting for the response */
> +	if (connection->reply.ret) {
> +		ret = connection->reply.ret;
> +		if (ret != -ENOMEM)
> +			kfree(connection->payload);
> +		goto out;
> +	}
> +
> +	/* Got a response, did resource manager give us an error? */
> +	if (connection->reply.rm_error != GH_RM_ERROR_OK) {
> +		dev_warn(rm->dev, "RM rejected message %08x. Error: %d\n", message_id,
> +			connection->reply.rm_error);
> +		dump_stack();
> +		ret = gh_rm_remap_error(connection->reply.rm_error);
> +		kfree(connection->payload);
> +		goto out;
> +	}
> +
> +	/* Everything looks good, return the payload */
> +	if (resp_buf_size)
> +		*resp_buf_size = connection->size;
> +	if (connection->size && resp_buf)
> +		*resp_buf = connection->payload;
> +	else {
> +		/* kfree in case RM sent us multiple fragments but never any data in
> +		 * those fragments. We would've allocated memory for it, but connection->size == 0
> +		 */
> +		kfree(connection->payload);
> +	}
> +
> +out:
> +	xa_erase(&rm->call_xarray, connection->reply.seq);
> +free:
> +	kfree(connection);
> +	return ret;
> +}
> +
> +
> +int gh_rm_notifier_register(struct gh_rm *rm, struct notifier_block *nb)
> +{
> +	return blocking_notifier_chain_register(&rm->nh, nb);
> +}
> +EXPORT_SYMBOL_GPL(gh_rm_notifier_register);
> +
> +int gh_rm_notifier_unregister(struct gh_rm *rm, struct notifier_block *nb)
> +{
> +	return blocking_notifier_chain_unregister(&rm->nh, nb);
> +}
> +EXPORT_SYMBOL_GPL(gh_rm_notifier_unregister);
> +
> +static int gh_msgq_platform_probe_direction(struct platform_device *pdev, bool tx,
> +					    struct gh_resource *ghrsc)
> +{
> +	struct device_node *node = pdev->dev.of_node;
> +	int ret;
> +	int idx = tx ? 0 : 1;
> +
> +	ghrsc->type = tx ? GH_RESOURCE_TYPE_MSGQ_TX : GH_RESOURCE_TYPE_MSGQ_RX;
> +
> +	ghrsc->irq = platform_get_irq(pdev, idx);
> +	if (ghrsc->irq < 0) {
> +		dev_err(&pdev->dev, "Failed to get irq%d: %d\n", idx, ghrsc->irq);
> +		return ghrsc->irq;
> +	}
> +
> +	ret = of_property_read_u64_index(node, "reg", idx, &ghrsc->capid);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Failed to get capid%d: %d\n", idx, ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int gh_identify(void)
> +{
> +	struct gh_hypercall_hyp_identify_resp gh_api;
> +
> +	if (!arch_is_gh_guest())
> +		return -ENODEV;
> +
> +	gh_hypercall_hyp_identify(&gh_api);
> +
> +	pr_info("Running under Gunyah hypervisor %llx/v%u\n",
> +		FIELD_GET(GH_API_INFO_VARIANT_MASK, gh_api.api_info),
> +		gh_api_version(&gh_api));
> +
> +	/* We might move this out to individual drivers if there's ever an API version bump */
> +	if (gh_api_version(&gh_api) != GH_API_V1) {
> +		pr_info("Unsupported Gunyah version: %u\n", gh_api_version(&gh_api));
> +		return -ENODEV;
> +	}
> +
> +	return 0;
> +}
> +
> +static int gh_rm_drv_probe(struct platform_device *pdev)
> +{
> +	struct gh_msgq_tx_data *msg;
> +	struct gh_rm *rm;
> +	int ret;
> +
> +	ret = gh_identify();
> +	if (ret)
> +		return ret;
> +
> +	rm = devm_kzalloc(&pdev->dev, sizeof(*rm), GFP_KERNEL);
> +	if (!rm)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, rm);
> +	rm->dev = &pdev->dev;
> +
> +	mutex_init(&rm->send_lock);
> +	BLOCKING_INIT_NOTIFIER_HEAD(&rm->nh);
> +	xa_init_flags(&rm->call_xarray, XA_FLAGS_ALLOC);
> +	rm->cache = kmem_cache_create("gh_rm", struct_size(msg, data, GH_MSGQ_MAX_MSG_SIZE), 0,
> +		SLAB_HWCACHE_ALIGN, NULL);
> +	if (!rm->cache)
> +		return -ENOMEM;
> +
> +	ret = gh_msgq_platform_probe_direction(pdev, true, &rm->tx_ghrsc);
> +	if (ret)
> +		goto err_cache;
> +
> +	ret = gh_msgq_platform_probe_direction(pdev, false, &rm->rx_ghrsc);
> +	if (ret)
> +		goto err_cache;
> +
> +	rm->msgq_client.dev = &pdev->dev;
> +	rm->msgq_client.tx_block = true;
> +	rm->msgq_client.rx_callback = gh_rm_msgq_rx_data;
> +	rm->msgq_client.tx_done = gh_rm_msgq_tx_done;
> +
> +	return gh_msgq_init(&pdev->dev, &rm->msgq, &rm->msgq_client, &rm->tx_ghrsc, &rm->rx_ghrsc);
> +err_cache:
> +	kmem_cache_destroy(rm->cache);
> +	return ret;
> +}
> +
> +static int gh_rm_drv_remove(struct platform_device *pdev)
> +{
> +	struct gh_rm *rm = platform_get_drvdata(pdev);
> +
> +	mbox_free_channel(gh_msgq_chan(&rm->msgq));
> +	gh_msgq_remove(&rm->msgq);
> +	kmem_cache_destroy(rm->cache);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id gh_rm_of_match[] = {
> +	{ .compatible = "gunyah-resource-manager" },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, gh_rm_of_match);
> +
> +static struct platform_driver gh_rm_driver = {
> +	.probe = gh_rm_drv_probe,
> +	.remove = gh_rm_drv_remove,
> +	.driver = {
> +		.name = "gh_rsc_mgr",
> +		.of_match_table = gh_rm_of_match,
> +	},
> +};
> +module_platform_driver(gh_rm_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("Gunyah Resource Manager Driver");
> diff --git a/drivers/virt/gunyah/rsc_mgr.h b/drivers/virt/gunyah/rsc_mgr.h
> new file mode 100644
> index 000000000000..8309b7bf4668
> --- /dev/null
> +++ b/drivers/virt/gunyah/rsc_mgr.h
> @@ -0,0 +1,16 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (c) 2022-2023 Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +#ifndef __GH_RSC_MGR_PRIV_H
> +#define __GH_RSC_MGR_PRIV_H
> +
> +#include <linux/gunyah.h>
> +#include <linux/gunyah_rsc_mgr.h>
> +#include <linux/types.h>
> +
> +struct gh_rm;
> +int gh_rm_call(struct gh_rm *rsc_mgr, u32 message_id, const void *req_buf, size_t req_buf_size,
> +		void **resp_buf, size_t *resp_buf_size);
> +
> +#endif
> diff --git a/include/linux/gunyah_rsc_mgr.h b/include/linux/gunyah_rsc_mgr.h
> new file mode 100644
> index 000000000000..f2a312e80af5
> --- /dev/null
> +++ b/include/linux/gunyah_rsc_mgr.h
> @@ -0,0 +1,21 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (c) 2022-2023 Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +
> +#ifndef _GUNYAH_RSC_MGR_H
> +#define _GUNYAH_RSC_MGR_H
> +
> +#include <linux/list.h>
> +#include <linux/notifier.h>
> +#include <linux/gunyah.h>
> +
> +#define GH_VMID_INVAL		U16_MAX
> +
> +struct gh_rm;
> +int gh_rm_notifier_register(struct gh_rm *rm, struct notifier_block *nb);
> +int gh_rm_notifier_unregister(struct gh_rm *rm, struct notifier_block *nb);
> +struct device *gh_rm_get(struct gh_rm *rm);
> +void gh_rm_put(struct gh_rm *rm);
> +
> +#endif