[PATCH v4] vfio: fix workaround of BAR0 mapping

[Takeshi Yoshimura <t.yoshimura8869@gmail.com>]

The workaround of BAR0 mapping gives up and immediately returns an
error if it cannot map around the MSI-X. However, recent version
of VFIO allows MSIX mapping (*).

I fixed not to return immediately but try mapping. In old Linux, mmap
just fails and returns the same error as the code before my fix . In
recent Linux, mmap succeeds and this patch enables running DPDK in
specific environments (e.g., ppc64le with HGST NVMe)

(*): "vfio-pci: Allow mapping MSIX BAR",
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/
commit/id=a32295c612c57990d17fb0f41e7134394b2f35f6

Fixes: 90a1633b2347 ("eal/linux: allow to map BARs with MSI-X tables")

Signed-off-by: Takeshi Yoshimura <t.yoshimura8869@gmail.com>
---
 drivers/bus/pci/linux/pci_vfio.c | 92 ++++++++++++++++++++++------------------
 1 file changed, 51 insertions(+), 41 deletions(-)

diff --git a/drivers/bus/pci/linux/pci_vfio.c b/drivers/bus/pci/linux/pci_vfio.c
index aeeaa9ed8..afdf0f6d5 100644
--- a/drivers/bus/pci/linux/pci_vfio.c
+++ b/drivers/bus/pci/linux/pci_vfio.c
@@ -332,50 +332,58 @@ pci_vfio_mmap_bar(int vfio_dev_fd, struct mapped_pci_resource *vfio_res,
 	void *bar_addr;
 	struct pci_msix_table *msix_table = &vfio_res->msix_table;
 	struct pci_map *bar = &vfio_res->maps[bar_index];
+	bool again = false;
 
 	if (bar->size == 0)
 		/* Skip this BAR */
 		return 0;
 
-	if (msix_table->bar_index == bar_index) {
-		/*
-		 * VFIO will not let us map the MSI-X table,
-		 * but we can map around it.
-		 */
-		uint32_t table_start = msix_table->offset;
-		uint32_t table_end = table_start + msix_table->size;
-		table_end = (table_end + ~PAGE_MASK) & PAGE_MASK;
-		table_start &= PAGE_MASK;
-
-		if (table_start == 0 && table_end >= bar->size) {
-			/* Cannot map this BAR */
-			RTE_LOG(DEBUG, EAL, "Skipping BAR%d\n", bar_index);
-			bar->size = 0;
-			bar->addr = 0;
-			return 0;
-		}
-
-		memreg[0].offset = bar->offset;
-		memreg[0].size = table_start;
-		memreg[1].offset = bar->offset + table_end;
-		memreg[1].size = bar->size - table_end;
-
-		RTE_LOG(DEBUG, EAL,
-			"Trying to map BAR%d that contains the MSI-X "
-			"table. Trying offsets: "
-			"0x%04lx:0x%04lx, 0x%04lx:0x%04lx\n", bar_index,
-			memreg[0].offset, memreg[0].size,
-			memreg[1].offset, memreg[1].size);
-	} else {
-		memreg[0].offset = bar->offset;
-		memreg[0].size = bar->size;
-	}
-
 	/* reserve the address using an inaccessible mapping */
 	bar_addr = mmap(bar->addr, bar->size, 0, MAP_PRIVATE |
 			MAP_ANONYMOUS | additional_flags, -1, 0);
-	if (bar_addr != MAP_FAILED) {
+	if (bar_addr == MAP_FAILED) {
+		RTE_LOG(ERR, EAL,
+			"Failed to create inaccessible mapping for BAR%d\n",
+			bar_index);
+		return -1;
+	}
+
+	memreg[0].offset = bar->offset;
+	memreg[0].size = bar->size;
+	do {
 		void *map_addr = NULL;
+		if (again) {
+			/*
+			 * VFIO did not let us map the MSI-X table,
+			 * but we can map around it.
+			 */
+			uint32_t table_start = msix_table->offset;
+			uint32_t table_end = table_start + msix_table->size;
+			table_end = (table_end + ~PAGE_MASK) & PAGE_MASK;
+			table_start &= PAGE_MASK;
+
+			if (table_start == 0 && table_end >= bar->size) {
+				/* Cannot map this BAR */
+				RTE_LOG(DEBUG, EAL, "Skipping BAR%d\n",
+						bar_index);
+				bar->size = 0;
+				bar->addr = 0;
+				return 0;
+			}
+
+			memreg[0].offset = bar->offset;
+			memreg[0].size = table_start;
+			memreg[1].offset = bar->offset + table_end;
+			memreg[1].size = bar->size - table_end;
+
+			RTE_LOG(DEBUG, EAL,
+				"Trying to map BAR%d that contains the MSI-X "
+				"table. Trying offsets: "
+				"0x%04lx:0x%04lx, 0x%04lx:0x%04lx\n", bar_index,
+				memreg[0].offset, memreg[0].size,
+				memreg[1].offset, memreg[1].size);
+		}
+
 		if (memreg[0].size) {
 			/* actual map of first part */
 			map_addr = pci_map_resource(bar_addr, vfio_dev_fd,
@@ -384,6 +392,12 @@ pci_vfio_mmap_bar(int vfio_dev_fd, struct mapped_pci_resource *vfio_res,
 							MAP_FIXED);
 		}
 
+		if (map_addr == MAP_FAILED &&
+			msix_table->bar_index == bar_index && !again) {
+			again = true;
+			continue;
+		}
+
 		/* if there's a second part, try to map it */
 		if (map_addr != MAP_FAILED
 			&& memreg[1].offset && memreg[1].size) {
@@ -404,12 +418,8 @@ pci_vfio_mmap_bar(int vfio_dev_fd, struct mapped_pci_resource *vfio_res,
 					bar_index);
 			return -1;
 		}
-	} else {
-		RTE_LOG(ERR, EAL,
-				"Failed to create inaccessible mapping for BAR%d\n",
-				bar_index);
-		return -1;
-	}
+		break;
+	} while (again);
 
 	bar->addr = bar_addr;
 	return 0;
-- 
2.15.1