[dpdk-dev] [PATCH v3] 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>
---

Thanks, Anatoly.

I updated the patch not to affect behaviors of older Linux and
other environments as well as possible. This patch adds another
chance to mmap BAR0.

I noticed that the check at line 350 already includes the check
of page size, so this patch does not fix the check.

Regards,
Takeshi

drivers/bus/pci/linux/pci_vfio.c | 35 ++++++++++++++++++-----------------
 1 file changed, 18 insertions(+), 17 deletions(-)

diff --git a/drivers/bus/pci/linux/pci_vfio.c b/drivers/bus/pci/linux/pci_vfio.c
index aeeaa9ed8..eb9b8031d 100644
--- a/drivers/bus/pci/linux/pci_vfio.c
+++ b/drivers/bus/pci/linux/pci_vfio.c
@@ -348,24 +348,25 @@ pci_vfio_mmap_bar(int vfio_dev_fd, struct mapped_pci_resource *vfio_res,
 		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;
+			/* Cannot map around this BAR, but try */
+			RTE_LOG(DEBUG, EAL,
+				"Trying to map BAR%d that contains the MSI-X\n",
+				bar_index);
+			memreg[0].offset = bar->offset;
+			memreg[0].size = bar->size;
+		} else {
+			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);
 		}
-
-		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;
-- 
2.15.1