Spdk/lib/vhost/rte_vhost_compat.c

/*-
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 *
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 *       from this software without specific prior written permission.
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/** \file
 * Set of workarounds for rte_vhost to make it work with device types
 * other than vhost-net.
 */

#include "spdk/stdinc.h"

#include "spdk/env.h"
#include "spdk/likely.h"
#include "spdk/string.h"
#include "spdk/util.h"
#include "spdk/barrier.h"
#include "spdk/vhost.h"
#include "vhost_internal.h"

#include "spdk_internal/vhost_user.h"

#ifndef SPDK_CONFIG_VHOST_INTERNAL_LIB
extern const struct vhost_device_ops g_spdk_vhost_ops;

static enum rte_vhost_msg_result
spdk_extern_vhost_pre_msg_handler(int vid, void *_msg)
{
	struct vhost_user_msg *msg = _msg;
	struct spdk_vhost_session *vsession;

	vsession = spdk_vhost_session_find_by_vid(vid);
	if (vsession == NULL) {
		SPDK_ERRLOG("Received a message to unitialized session (vid %d).\n", vid);
		assert(false);
		return RTE_VHOST_MSG_RESULT_ERR;
	}

	switch (msg->request) {
	case VHOST_USER_GET_VRING_BASE:
		if (vsession->forced_polling && vsession->lcore != -1) {
			/* Our queue is stopped for whatever reason, but we may still
			 * need to poll it after it's initialized again.
			 */
			g_spdk_vhost_ops.destroy_device(vid);
		}
		break;
	case VHOST_USER_SET_VRING_BASE:
	case VHOST_USER_SET_VRING_ADDR:
	case VHOST_USER_SET_VRING_NUM:
	case VHOST_USER_SET_VRING_KICK:
		if (vsession->forced_polling && vsession->lcore != -1) {
			/* Additional queues are being initialized, so we either processed
			 * enough I/Os and are switching from SeaBIOS to the OS now, or
			 * we were never in SeaBIOS in the first place. Either way, we
			 * don't need our workaround anymore.
			 */
			g_spdk_vhost_ops.destroy_device(vid);
			vsession->forced_polling = false;
		}
		break;
	case VHOST_USER_SET_VRING_CALL:
		/* rte_vhost will close the previous callfd and won't notify
		 * us about any change. This will effectively make SPDK fail
		 * to deliver any subsequent interrupts until a session is
		 * restarted. We stop the session here before closing the previous
		 * fd (so that all interrupts must have been delivered by the
		 * time the descriptor is closed) and start right after (which
		 * will make SPDK retrieve the latest, up-to-date callfd from
		 * rte_vhost.
		 */
	case VHOST_USER_SET_MEM_TABLE:
		/* rte_vhost will unmap previous memory that SPDK may still
		 * have pending DMA operations on. We can't let that happen,
		 * so stop the device before letting rte_vhost unmap anything.
		 * This will block until all pending I/Os are finished.
		 * We will start the device again from the post-processing
		 * message handler.
		 */
		if (vsession->lcore != -1) {
			g_spdk_vhost_ops.destroy_device(vid);
			vsession->needs_restart = true;
		}
		break;
	default:
		break;
	}

	return RTE_VHOST_MSG_RESULT_NOT_HANDLED;
}

static enum rte_vhost_msg_result
spdk_extern_vhost_post_msg_handler(int vid, void *_msg)
{
	struct vhost_user_msg *msg = _msg;
	struct spdk_vhost_session *vsession;

	vsession = spdk_vhost_session_find_by_vid(vid);
	if (vsession == NULL) {
		SPDK_ERRLOG("Received a message to unitialized session (vid %d).\n", vid);
		assert(false);
		return RTE_VHOST_MSG_RESULT_ERR;
	}

	if (vsession->needs_restart) {
		g_spdk_vhost_ops.new_device(vid);
		vsession->needs_restart = false;
		return RTE_VHOST_MSG_RESULT_NOT_HANDLED;
	}

	switch (msg->request) {
	case VHOST_USER_SET_FEATURES:
		/* rte_vhost requires all queues to be fully initialized in order
		 * to start I/O processing. This behavior is not compliant with the
		 * vhost-user specification and doesn't work with QEMU 2.12+, which
		 * will only initialize 1 I/O queue for the SeaBIOS boot.
		 * Theoretically, we should start polling each virtqueue individually
		 * after receiving its SET_VRING_KICK message, but rte_vhost is not
		 * designed to poll individual queues. So here we use a workaround
		 * to detect when the vhost session could be potentially at that SeaBIOS
		 * stage and we mark it to start polling as soon as its first virtqueue
		 * gets initialized. This doesn't hurt any non-QEMU vhost slaves
		 * and allows QEMU 2.12+ to boot correctly. SET_FEATURES could be sent
		 * at any time, but QEMU will send it at least once on SeaBIOS
		 * initialization - whenever powered-up or rebooted.
		 */
		vsession->forced_polling = true;
		break;
	case VHOST_USER_SET_VRING_KICK:
		/* vhost-user spec tells us to start polling a queue after receiving
		 * its SET_VRING_KICK message. Let's do it!
		 */
		if (vsession->forced_polling && vsession->lcore == -1) {
			g_spdk_vhost_ops.new_device(vid);
		}
		break;
	default:
		break;
	}

	return RTE_VHOST_MSG_RESULT_NOT_HANDLED;
}

struct rte_vhost_user_extern_ops g_spdk_extern_vhost_ops = {
	.pre_msg_handle = spdk_extern_vhost_pre_msg_handler,
	.post_msg_handle = spdk_extern_vhost_post_msg_handler,
};

void
spdk_vhost_session_install_rte_compat_hooks(struct spdk_vhost_session *vsession)
{
	int rc;

	rc = rte_vhost_extern_callback_register(vsession->vid, &g_spdk_extern_vhost_ops, NULL);
	if (rc != 0) {
		SPDK_ERRLOG("rte_vhost_extern_callback_register() failed for vid = %d\n",
			    vsession->vid);
		return;
	}
}

#else /* SPDK_CONFIG_VHOST_INTERNAL_LIB */
void
spdk_vhost_session_install_rte_compat_hooks(struct spdk_vhost_session *vsession)
{
	/* nothing to do. all the changes are already incorporated into rte_vhost */
}
#endif