examples: add fault queue example

Add example using the iommufd fault queue to handle device page faults.

This example is intended to be used with the QEMU pcie-ats-testdev
device. See QEMU for documentation.

Signed-off-by: Klaus Jensen <[email protected]>

examples/iopf.c

@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+/*
+ * This file is part of libvfn.
+ *
+ * Copyright (C) 2022 The libvfn Authors. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+
+#include <inttypes.h>
+
+#include <sys/mman.h>
+
+#include <linux/iommufd.h>
+
+#include <vfn/vfio.h>
+#include <vfn/iommu.h>
+#include <vfn/iommu/iommufd.h>
+#include <vfn/support.h>
+
+#include "ccan/err/err.h"
+#include "ccan/opt/opt.h"
+#include "ccan/str/str.h"
+
+#include "common.h"
+
+#define REG_ADDR 0x0
+#define REG_CMD  0x8
+
+#define IOVA_BASE 0xfef00000
+
+static struct opt_table opts[] = {
+	OPT_SUBTABLE(opts_base, NULL),
+	OPT_ENDTABLE,
+};
+
+struct vfio_pci_device pdev;
+
+int main(int argc, char **argv)
+{
+	void *bar0;
+	uint64_t iova = IOVA_BASE;
+	ssize_t len;
+	void *vaddr;
+
+	struct iommufd_fault_queue fq;
+
+	struct iommu_hwpt_pgfault pgfault;
+	struct iommu_hwpt_page_response pgresp = {
+		.code = IOMMUFD_PAGE_RESP_SUCCESS,
+	};
+
+	opt_register_table(opts, NULL);
+	opt_parse(&argc, argv, opt_log_stderr_exit);
+
+	if (show_usage)
+		opt_usage_and_exit(NULL);
+
+	if (streq(bdf, ""))
+		opt_usage_exit_fail("missing --device parameter");
+
+	opt_free_table();
+
+	if (vfio_pci_open(&pdev, bdf))
+		err(1, "failed to open pci device");
+
+	if (iommufd_alloc_fault_queue(&fq))
+		err(1, "could not allocate fault queue");
+
+	if (iommufd_set_fault_queue(pdev.dev.ctx, &fq, pdev.dev.fd))
+		err(1, "could not associate fault queue with device/ioas");
+
+	bar0 = vfio_pci_map_bar(&pdev, 0, 0x1000, 0, PROT_READ | PROT_WRITE);
+	if (!bar0)
+		err(1, "failed to map bar");
+
+	len = pgmap(&vaddr, 0x1000);
+	if (len < 0)
+		err(1, "could not allocate aligned memory");
+
+	memset(vaddr, 0x42, 0x1000);
+
+	mmio_lh_write64(bar0 + REG_ADDR, iova);
+	mmio_write32(bar0 + REG_CMD, 0x3);
+
+	/* wait for page fault */
+	while (read(fq.fault_fd, &pgfault, sizeof(pgfault)) == 0)
+		;
+
+	printf("handling page fault on addr 0x%llx\n", pgfault.addr);
+
+	if (iommu_map_vaddr(pdev.dev.ctx, vaddr, 0x1000, &iova, IOMMU_MAP_FIXED_IOVA))
+		err(1, "failed to map page");
+
+	pgresp.cookie = pgfault.cookie;
+
+	if (write(fq.fault_fd, &pgresp, sizeof(pgresp)) < 0)
+		err(1, "failed to write page response");
+
+	while (mmio_read32(bar0 + REG_CMD) & 0x1)
+		;
+
+	memset(vaddr, 0x0, 0x1000);
+
+	mmio_write32(bar0 + REG_CMD, 0x1);
+
+	while (mmio_read32(bar0 + REG_CMD) & 0x1)
+		;
+
+	for (int i = 0; i < 0x1000; i++) {
+		uint8_t byte = *(uint8_t *)(vaddr + i);
+
+		if (byte != 0x42)
+			errx(1, "unexpected byte 0x%"PRIx8, byte);
+	}
+
+	return 0;
+}

examples/meson.build

@@ -16,10 +16,14 @@ examples = {
   'regs': ['regs.c'],
 }
 
+if config_host.get('HAVE_IOMMU_FAULT_QUEUE_ALLOC', false)
+  examples += {'iopf': ['iopf.c']}
+endif
+
 foreach example, sources : examples
   executable(example, [example_sources, sources],
     dependencies: [libnvme],
     link_with: [ccan_lib, vfn_lib],
-    include_directories: [ccan_inc, vfn_inc],
+    include_directories: [ccan_inc, vfn_inc, linux_headers],
   )
 endforeach