um: add PCI over virtio emulation driver

To support testing of PCI/PCIe drivers in UML, add a PCI bus
support driver. This driver uses virtio, which in UML is really
just vhost-user, to talk to devices, and adds the devices to
the virtual PCI bus in the system.

Since virtio already allows DMA/bus mastering this really isn't
all that hard, of course we need the logic_iomem infrastructure
that was added by a previous patch.

The protocol to talk to the device is has a few fairly simple
messages for reading to/writing from config and IO spaces, and
messages for the device to send the various interrupts (INT#,
MSI/MSI-X and while suspended PME#).

Note that currently no offical virtio device ID is assigned for
this protocol, as a consequence this patch requires defining it
in the Kconfig, with a default that makes the driver refuse to
work at all.

Finally, in order to add support for MSI/MSI-X interrupts, some
small changes are needed in the UML IRQ code, it needs to have
more interrupts, changing NR_IRQS from 64 to 128 if this driver
is enabled, but not actually use them for anything so that the
generic IRQ domain/MSI infrastructure can allocate IRQ numbers.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

1 files changed, 64 insertions, 0 deletions

diff --git a/include/uapi/linux/virtio_pcidev.h b/include/uapi/linux/virtio_pcidev.h
new file mode 100644
index 000000000000..89daa88bcfef
--- /dev/null
+++ b/include/uapi/linux/virtio_pcidev.h
@@ -0,0 +1,64 @@
+/* SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) */
+/*
+ * Copyright (C) 2021 Intel Corporation
+ * Author: Johannes Berg <johannes@sipsolutions.net>
+ */
+#ifndef _UAPI_LINUX_VIRTIO_PCIDEV_H
+#define _UAPI_LINUX_VIRTIO_PCIDEV_H
+#include <linux/types.h>
+
+/**
+ * enum virtio_pcidev_ops - virtual PCI device operations
+ * @VIRTIO_PCIDEV_OP_CFG_READ: read config space, size is 1, 2, 4 or 8;
+ *	the @data field should be filled in by the device (in little endian).
+ * @VIRTIO_PCIDEV_OP_CFG_WRITE: write config space, size is 1, 2, 4 or 8;
+ *	the @data field contains the data to write (in little endian).
+ * @VIRTIO_PCIDEV_OP_BAR_READ: read BAR mem/pio, size can be variable;
+ *	the @data field should be filled in by the device (in little endian).
+ * @VIRTIO_PCIDEV_OP_BAR_WRITE: write BAR mem/pio, size can be variable;
+ *	the @data field contains the data to write (in little endian).
+ * @VIRTIO_PCIDEV_OP_MMIO_MEMSET: memset MMIO, size is variable but
+ *	the @data field only has one byte (unlike @VIRTIO_PCIDEV_OP_MMIO_WRITE)
+ * @VIRTIO_PCIDEV_OP_INT: legacy INTx# pin interrupt, the addr field is 1-4 for
+ *	the number
+ * @VIRTIO_PCIDEV_OP_MSI: MSI(-X) interrupt, this message basically transports
+ *	the 16- or 32-bit write that would otherwise be done into memory,
+ *	analogous to the write messages (@VIRTIO_PCIDEV_OP_MMIO_WRITE) above
+ * @VIRTIO_PCIDEV_OP_PME: Dummy message whose content is ignored (and should be
+ *	all zeroes) to signal the PME# pin.
+ */
+enum virtio_pcidev_ops {
+	VIRTIO_PCIDEV_OP_RESERVED = 0,
+	VIRTIO_PCIDEV_OP_CFG_READ,
+	VIRTIO_PCIDEV_OP_CFG_WRITE,
+	VIRTIO_PCIDEV_OP_MMIO_READ,
+	VIRTIO_PCIDEV_OP_MMIO_WRITE,
+	VIRTIO_PCIDEV_OP_MMIO_MEMSET,
+	VIRTIO_PCIDEV_OP_INT,
+	VIRTIO_PCIDEV_OP_MSI,
+	VIRTIO_PCIDEV_OP_PME,
+};
+
+/**
+ * struct virtio_pcidev_msg - virtio PCI device operation
+ * @op: the operation to do
+ * @bar: the bar (only with BAR read/write messages)
+ * @reserved: reserved
+ * @size: the size of the read/write (in bytes)
+ * @addr: the address to read/write
+ * @data: the data, normally @size long, but just one byte for
+ *	%VIRTIO_PCIDEV_OP_MMIO_MEMSET
+ *
+ * Note: the fields are all in native (CPU) endian, however, the
+ * @data values will often be in little endian (see the ops above.)
+ */
+struct virtio_pcidev_msg {
+	__u8 op;
+	__u8 bar;
+	__u16 reserved;
+	__u32 size;
+	__u64 addr;
+	__u8 data[];
+};
+
+#endif /* _UAPI_LINUX_VIRTIO_PCIDEV_H */