On 6/20/25 4:20 PM, David Matlack wrote:
> 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 <psh...@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.ji...@intel.com>
> Cc: Dan Williams <dan.j.willi...@intel.com>
> Signed-off-by: David Matlack <dmatl...@google.com>
Acked-by: Dave Jiang <dave.ji...@intel.com>
> ---
> .../selftests/vfio/lib/drivers/ioat/hw.h | 1 +
> .../selftests/vfio/lib/drivers/ioat/ioat.c | 235 ++++++++++++++++++
> .../vfio/lib/drivers/ioat/registers.h | 1 +
> tools/testing/selftests/vfio/lib/libvfio.mk | 7 +
> .../selftests/vfio/lib/vfio_pci_driver.c | 10 +-
> 5 files changed, 253 insertions(+), 1 deletion(-)
> create mode 120000 tools/testing/selftests/vfio/lib/drivers/ioat/hw.h
> create mode 100644 tools/testing/selftests/vfio/lib/drivers/ioat/ioat.c
> create mode 120000 tools/testing/selftests/vfio/lib/drivers/ioat/registers.h
>
> diff --git a/tools/testing/selftests/vfio/lib/drivers/ioat/hw.h
> b/tools/testing/selftests/vfio/lib/drivers/ioat/hw.h
> new file mode 120000
> index 000000000000..8ab52ddd4458
> --- /dev/null
> +++ b/tools/testing/selftests/vfio/lib/drivers/ioat/hw.h
> @@ -0,0 +1 @@
> +../../../../../../../drivers/dma/ioat/hw.h
> \ No newline at end of file
> diff --git a/tools/testing/selftests/vfio/lib/drivers/ioat/ioat.c
> b/tools/testing/selftests/vfio/lib/drivers/ioat/ioat.c
> new file mode 100644
> index 000000000000..c3b91d9b1f59
> --- /dev/null
> +++ b/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,
> +};
> diff --git a/tools/testing/selftests/vfio/lib/drivers/ioat/registers.h
> b/tools/testing/selftests/vfio/lib/drivers/ioat/registers.h
> new file mode 120000
> index 000000000000..0b809cfd8fe6
> --- /dev/null
> +++ b/tools/testing/selftests/vfio/lib/drivers/ioat/registers.h
> @@ -0,0 +1 @@
> +../../../../../../../drivers/dma/ioat/registers.h
> \ No newline at end of file
> diff --git a/tools/testing/selftests/vfio/lib/libvfio.mk
> b/tools/testing/selftests/vfio/lib/libvfio.mk
> index a3c3bc9a7c00..624dc267a879 100644
> --- a/tools/testing/selftests/vfio/lib/libvfio.mk
> +++ b/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)
> diff --git a/tools/testing/selftests/vfio/lib/vfio_pci_driver.c
> b/tools/testing/selftests/vfio/lib/vfio_pci_driver.c
> index c98bd2d31d8a..aa47360e47a9 100644
> --- a/tools/testing/selftests/vfio/lib/vfio_pci_driver.c
> +++ b/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)
> {
