Re: [PATCH 20/33] vfio: selftests: Add driver for Intel CBDMA

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 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 Signed-off-by: David Matlack dmatlack@google.com

Acked-by: Dave Jiang dave.jiang@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) {