vfio: selftests: Add driver for Intel CBDMA

Add a driver for the Intel CBDMA device. This driver is based on and
named after the Linux driver for this device (drivers/dma/ioat/) and
also based on previous work from Peter Shier <pshier@google.com>.

The driver aims to be as simple as possible. It uses a single descriptor
to issue DMA operations, and only supports the copy operation. For "DMA
storms", the driver kicks off the maximum number of maximum-sized DMA
operations. On Skylake server parts, this was 2^16-1 copies of size 2M
and lasts about 15 seconds.

Create symlinks to drivers/dma/ioat/{hw.h,registers.h} to get access to
various macros (e.g. IOAT_CHANCMD_RESET) and struct ioat_dma_descriptor.

Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Acked-by: Dave Jiang <dave.jiang@intel.com>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: David Matlack <dmatlack@google.com>
Link: https://lore.kernel.org/r/20250822212518.4156428-20-dmatlack@google.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

tools/testing/selftests/vfio/lib/drivers/ioat/hw.h

@@ -0,0 +1 @@
+../../../../../../../drivers/dma/ioat/hw.h

tools/testing/selftests/vfio/lib/drivers/ioat/ioat.c

@@ -0,0 +1,235 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <stdint.h>
+#include <unistd.h>
+
+#include <linux/errno.h>
+#include <linux/io.h>
+#include <linux/pci_ids.h>
+#include <linux/sizes.h>
+
+#include <vfio_util.h>
+
+#include "hw.h"
+#include "registers.h"
+
+#define IOAT_DMACOUNT_MAX UINT16_MAX
+
+struct ioat_state {
+	/* Single descriptor used to issue DMA memcpy operations */
+	struct ioat_dma_descriptor desc;
+
+	/* Copy buffers used by ioat_send_msi() to generate an interrupt. */
+	u64 send_msi_src;
+	u64 send_msi_dst;
+};
+
+static inline struct ioat_state *to_ioat_state(struct vfio_pci_device *device)
+{
+	return device->driver.region.vaddr;
+}
+
+static inline void *ioat_channel_registers(struct vfio_pci_device *device)
+{
+	return device->bars[0].vaddr + IOAT_CHANNEL_MMIO_SIZE;
+}
+
+static int ioat_probe(struct vfio_pci_device *device)
+{
+	u8 version;
+	int r;
+
+	if (!vfio_pci_device_match(device, PCI_VENDOR_ID_INTEL,
+				   PCI_DEVICE_ID_INTEL_IOAT_SKX))
+		return -EINVAL;
+
+	VFIO_ASSERT_NOT_NULL(device->bars[0].vaddr);
+
+	version = readb(device->bars[0].vaddr + IOAT_VER_OFFSET);
+	switch (version) {
+	case IOAT_VER_3_2:
+	case IOAT_VER_3_3:
+		r = 0;
+		break;
+	default:
+		printf("ioat: Unsupported version: 0x%x\n", version);
+		r = -EINVAL;
+	}
+	return r;
+}
+
+static u64 ioat_channel_status(void *bar)
+{
+	return readq(bar + IOAT_CHANSTS_OFFSET) & IOAT_CHANSTS_STATUS;
+}
+
+static void ioat_clear_errors(struct vfio_pci_device *device)
+{
+	void *registers = ioat_channel_registers(device);
+	u32 errors;
+
+	errors = vfio_pci_config_readl(device, IOAT_PCI_CHANERR_INT_OFFSET);
+	vfio_pci_config_writel(device, IOAT_PCI_CHANERR_INT_OFFSET, errors);
+
+	errors = vfio_pci_config_readl(device, IOAT_PCI_DMAUNCERRSTS_OFFSET);
+	vfio_pci_config_writel(device, IOAT_PCI_CHANERR_INT_OFFSET, errors);
+
+	errors = readl(registers + IOAT_CHANERR_OFFSET);
+	writel(errors, registers + IOAT_CHANERR_OFFSET);
+}
+
+static void ioat_reset(struct vfio_pci_device *device)
+{
+	void *registers = ioat_channel_registers(device);
+	u32 sleep_ms = 1, attempts = 5000 / sleep_ms;
+	u8 chancmd;
+
+	ioat_clear_errors(device);
+
+	writeb(IOAT_CHANCMD_RESET, registers + IOAT2_CHANCMD_OFFSET);
+
+	for (;;) {
+		chancmd = readb(registers + IOAT2_CHANCMD_OFFSET);
+		if (!(chancmd & IOAT_CHANCMD_RESET))
+			break;
+
+		VFIO_ASSERT_GT(--attempts, 0);
+		usleep(sleep_ms * 1000);
+	}
+
+	VFIO_ASSERT_EQ(ioat_channel_status(registers), IOAT_CHANSTS_HALTED);
+}
+
+static void ioat_init(struct vfio_pci_device *device)
+{
+	struct ioat_state *ioat = to_ioat_state(device);
+	u8 intrctrl;
+
+	VFIO_ASSERT_GE(device->driver.region.size, sizeof(*ioat));
+
+	vfio_pci_config_writew(device, PCI_COMMAND,
+			       PCI_COMMAND_MEMORY |
+			       PCI_COMMAND_MASTER |
+			       PCI_COMMAND_INTX_DISABLE);
+
+	ioat_reset(device);
+
+	/* Enable the use of MXI-x interrupts for channel interrupts. */
+	intrctrl = IOAT_INTRCTRL_MSIX_VECTOR_CONTROL;
+	writeb(intrctrl, device->bars[0].vaddr + IOAT_INTRCTRL_OFFSET);
+
+	vfio_pci_msix_enable(device, 0, device->msix_info.count);
+
+	device->driver.msi = 0;
+	device->driver.max_memcpy_size =
+		1UL << readb(device->bars[0].vaddr + IOAT_XFERCAP_OFFSET);
+	device->driver.max_memcpy_count = IOAT_DMACOUNT_MAX;
+}
+
+static void ioat_remove(struct vfio_pci_device *device)
+{
+	ioat_reset(device);
+	vfio_pci_msix_disable(device);
+}
+
+static void ioat_handle_error(struct vfio_pci_device *device)
+{
+	void *registers = ioat_channel_registers(device);
+
+	printf("Error detected during memcpy operation!\n"
+	       "  CHANERR: 0x%x\n"
+	       "  CHANERR_INT: 0x%x\n"
+	       "  DMAUNCERRSTS: 0x%x\n",
+	       readl(registers + IOAT_CHANERR_OFFSET),
+	       vfio_pci_config_readl(device, IOAT_PCI_CHANERR_INT_OFFSET),
+	       vfio_pci_config_readl(device, IOAT_PCI_DMAUNCERRSTS_OFFSET));
+
+	ioat_reset(device);
+}
+
+static int ioat_memcpy_wait(struct vfio_pci_device *device)
+{
+	void *registers = ioat_channel_registers(device);
+	u64 status;
+	int r = 0;
+
+	/* Wait until all operations complete. */
+	for (;;) {
+		status = ioat_channel_status(registers);
+		if (status == IOAT_CHANSTS_DONE)
+			break;
+
+		if (status == IOAT_CHANSTS_HALTED) {
+			ioat_handle_error(device);
+			return -1;
+		}
+	}
+
+	/* Put the channel into the SUSPENDED state. */
+	writeb(IOAT_CHANCMD_SUSPEND, registers + IOAT2_CHANCMD_OFFSET);
+	for (;;) {
+		status = ioat_channel_status(registers);
+		if (status == IOAT_CHANSTS_SUSPENDED)
+			break;
+	}
+
+	return r;
+}
+
+static void __ioat_memcpy_start(struct vfio_pci_device *device,
+				iova_t src, iova_t dst, u64 size,
+				u16 count, bool interrupt)
+{
+	void *registers = ioat_channel_registers(device);
+	struct ioat_state *ioat = to_ioat_state(device);
+	u64 desc_iova;
+	u16 chanctrl;
+
+	desc_iova = to_iova(device, &ioat->desc);
+	ioat->desc = (struct ioat_dma_descriptor) {
+		.ctl_f.op = IOAT_OP_COPY,
+		.ctl_f.int_en = interrupt,
+		.src_addr = src,
+		.dst_addr = dst,
+		.size = size,
+		.next = desc_iova,
+	};
+
+	/* Tell the device the address of the descriptor. */
+	writeq(desc_iova, registers + IOAT2_CHAINADDR_OFFSET);
+
+	/* (Re)Enable the channel interrupt and abort on any errors */
+	chanctrl = IOAT_CHANCTRL_INT_REARM | IOAT_CHANCTRL_ANY_ERR_ABORT_EN;
+	writew(chanctrl, registers + IOAT_CHANCTRL_OFFSET);
+
+	/* Kick off @count DMA copy operation(s). */
+	writew(count, registers + IOAT_CHAN_DMACOUNT_OFFSET);
+}
+
+static void ioat_memcpy_start(struct vfio_pci_device *device,
+			      iova_t src, iova_t dst, u64 size,
+			      u64 count)
+{
+	__ioat_memcpy_start(device, src, dst, size, count, false);
+}
+
+static void ioat_send_msi(struct vfio_pci_device *device)
+{
+	struct ioat_state *ioat = to_ioat_state(device);
+
+	__ioat_memcpy_start(device,
+			    to_iova(device, &ioat->send_msi_src),
+			    to_iova(device, &ioat->send_msi_dst),
+			    sizeof(ioat->send_msi_src), 1, true);
+
+	VFIO_ASSERT_EQ(ioat_memcpy_wait(device), 0);
+}
+
+const struct vfio_pci_driver_ops ioat_ops = {
+	.name = "ioat",
+	.probe = ioat_probe,
+	.init = ioat_init,
+	.remove = ioat_remove,
+	.memcpy_start = ioat_memcpy_start,
+	.memcpy_wait = ioat_memcpy_wait,
+	.send_msi = ioat_send_msi,
+};

tools/testing/selftests/vfio/lib/drivers/ioat/registers.h

@@ -0,0 +1 @@
+../../../../../../../drivers/dma/ioat/registers.h

tools/testing/selftests/vfio/lib/libvfio.mk

@@ -1,8 +1,15 @@
+include $(top_srcdir)/scripts/subarch.include
+ARCH ?= $(SUBARCH)
+
 VFIO_DIR := $(selfdir)/vfio
 
 LIBVFIO_C := lib/vfio_pci_device.c
 LIBVFIO_C += lib/vfio_pci_driver.c
 
+ifeq ($(ARCH:x86_64=x86),x86)
+LIBVFIO_C += lib/drivers/ioat/ioat.c
+endif
+
 LIBVFIO_O := $(patsubst %.c, $(OUTPUT)/%.o, $(LIBVFIO_C))
 
 LIBVFIO_O_DIRS := $(shell dirname $(LIBVFIO_O) | uniq)

tools/testing/selftests/vfio/lib/vfio_pci_driver.c

@@ -4,7 +4,15 @@
 #include "../../../kselftest.h"
 #include <vfio_util.h>
 
-static struct vfio_pci_driver_ops *driver_ops[] = {};
+#ifdef __x86_64__
+extern struct vfio_pci_driver_ops ioat_ops;
+#endif
+
+static struct vfio_pci_driver_ops *driver_ops[] = {
+#ifdef __x86_64__
+	&ioat_ops,
+#endif
+};
 
 void vfio_pci_driver_probe(struct vfio_pci_device *device)
 {