path: root/arch/um/drivers/virt-pci.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2020 Intel Corporation
 * Author: Johannes Berg <johannes@sipsolutions.net>
 */
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/virtio.h>
#include <linux/virtio_config.h>
#include <linux/logic_iomem.h>
#include <linux/of_platform.h>
#include <linux/irqdomain.h>
#include <linux/virtio_pcidev.h>
#include <linux/virtio-uml.h>
#include <linux/delay.h>
#include <linux/msi.h>
#include <asm/unaligned.h>
#include <irq_kern.h>

#define MAX_DEVICES 8
#define MAX_MSI_VECTORS 32
#define CFG_SPACE_SIZE 4096

/* for MSI-X we have a 32-bit payload */
#define MAX_IRQ_MSG_SIZE (sizeof(struct virtio_pcidev_msg) + sizeof(u32))
#define NUM_IRQ_MSGS	10

#define HANDLE_NO_FREE(ptr) ((void *)((unsigned long)(ptr) | 1))
#define HANDLE_IS_NO_FREE(ptr) ((unsigned long)(ptr) & 1)

struct um_pci_device {
	struct virtio_device *vdev;

	/* for now just standard BARs */
	u8 resptr[PCI_STD_NUM_BARS];

	struct virtqueue *cmd_vq, *irq_vq;

#define UM_PCI_STAT_WAITING	0
	unsigned long status;

	int irq;

	bool platform;
};

struct um_pci_device_reg {
	struct um_pci_device *dev;
	void __iomem *iomem;
};

static struct pci_host_bridge *bridge;
static DEFINE_MUTEX(um_pci_mtx);
static struct um_pci_device *um_pci_platform_device;
static struct um_pci_device_reg um_pci_devices[MAX_DEVICES];
static struct fwnode_handle *um_pci_fwnode;
static struct irq_domain *um_pci_inner_domain;
static struct irq_domain *um_pci_msi_domain;
static unsigned long um_pci_msi_used[BITS_TO_LONGS(MAX_MSI_VECTORS)];

static unsigned int um_pci_max_delay_us = 40000;
module_param_named(max_delay_us, um_pci_max_delay_us, uint, 0644);

struct um_pci_message_buffer {
	struct virtio_pcidev_msg hdr;
	u8 data[8];
};

static struct um_pci_message_buffer __percpu *um_pci_msg_bufs;

static int um_pci_send_cmd(struct um_pci_device *dev,
			   struct virtio_pcidev_msg *cmd,
			   unsigned int cmd_size,
			   const void *extra, unsigned int extra_size,
			   void *out, unsigned int out_size)
{
	struct scatterlist out_sg, extra_sg, in_sg;
	struct scatterlist *sgs_list[] = {
		[0] = &out_sg,
		[1] = extra ? &extra_sg : &in_sg,
		[2] = extra ? &in_sg : NULL,
	};
	struct um_pci_message_buffer *buf;
	int delay_count = 0;
	int ret, len;
	bool posted;

	if (WARN_ON(cmd_size < sizeof(*cmd) || cmd_size > sizeof(*buf)))
		return -EINVAL;

	switch (cmd->op) {
	case VIRTIO_PCIDEV_OP_CFG_WRITE:
	case VIRTIO_PCIDEV_OP_MMIO_WRITE:
	case VIRTIO_PCIDEV_OP_MMIO_MEMSET:
		/* in PCI, writes are posted, so don't wait */
		posted = !out;
		WARN_ON(!posted);
		break;
	default:
		posted = false;
		break;
	}

	buf = get_cpu_var(um_pci_msg_bufs);
	if (buf)
		memcpy(buf, cmd, cmd_size);

	if (posted) {
		u8 *ncmd = kmalloc(cmd_size + extra_size, GFP_ATOMIC);

		if (ncmd) {
			memcpy(ncmd, cmd, cmd_size);
			if (extra)
				memcpy(ncmd + cmd_size, extra, extra_size);
			cmd = (void *)ncmd;
			cmd_size += extra_size;
			extra = NULL;
			extra_size = 0;
		} else {
			/* try without allocating memory */
			posted = false;
			cmd = (void *)buf;
		}
	} else {
		cmd = (void *)buf;
	}

	sg_init_one(&out_sg, cmd, cmd_size);
	if (extra)
		sg_init_one(&extra_sg, extra, extra_size);
	if (out)
		sg_init_one(&in_sg, out, out_size);

	/* add to internal virtio queue */
	ret = virtqueue_add_sgs(dev->cmd_vq, sgs_list,
				extra ? 2 : 1,
				out ? 1 : 0,
				posted ? cmd : HANDLE_NO_FREE(cmd),
				GFP_ATOMIC);
	if (ret) {
		if (posted)
			kfree(cmd);
		goto out;
	}

	if (posted) {
		virtqueue_kick(dev->cmd_vq);
		ret = 0;
		goto out;
	}

	/* kick and poll for getting a response on the queue */
	set_bit(UM_PCI_STAT_WAITING, &dev->status);
	virtqueue_kick(dev->cmd_vq);

	while (1) {
		void *completed = virtqueue_get_buf(dev->cmd_vq, &len);

		if (completed == HANDLE_NO_FREE(cmd))
			break;

		if (completed && !HANDLE_IS_NO_FREE(completed))
			kfree(completed);

		if (WARN_ONCE(virtqueue_is_broken(dev->cmd_vq) ||
			      ++delay_count > um_pci_max_delay_us,
			      "um virt-pci delay: %d", delay_count)) {
			ret = -EIO;
			break;
		}
		udelay(1);