diff mbox series

[v4] vfio: fix workaround of BAR0 mapping

Message ID 20180717082230.3322-1-t.yoshimura8869@gmail.com (mailing list archive)
State Superseded, archived
Delegated to: Thomas Monjalon
Headers show
Series [v4] vfio: fix workaround of BAR0 mapping | expand

Checks

Context Check Description
ci/checkpatch success coding style OK
ci/Intel-compilation success Compilation OK

Commit Message

Takeshi Yoshimura July 17, 2018, 8:22 a.m. UTC
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(-)

Comments

Anatoly Burakov July 17, 2018, 10:08 a.m. UTC | #1
On 17-Jul-18 9:22 AM, Takeshi Yoshimura wrote:
> 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)

I don't think this applies to BAR0 only - it can be any BAR. Suggested 
rewording:

Currently, VFIO will try to map around MSI-X table in the BARs. When 
MSI-X table (page-aligned) size is equal to (page-aligned) size of BAR, 
VFIO will just skip the BAR.

Recent kernel versions will allow VFIO to map the entire BAR containing 
MSI-X tables (*), so instead of trying to map around the MSI-X vector or 
skipping the BAR entirely if it's not possible, we can now try mapping 
the entire BAR first. If mapping the entire BAR doesn't succeed, fall 
back to the old behavior of mapping around MSI-X table or skipping the BAR.

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

I think your link is wrong here - at least i can't find the commit when 
i copypaste the link into my browser.

> 
> Fixes: 90a1633b2347 ("eal/linux: allow to map BARs with MSI-X tables")
> 
> Signed-off-by: Takeshi Yoshimura <t.yoshimura8869@gmail.com>
> ---

<snip>

> +	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;

You have reserved space for the BAR earlier but do not unmap it on return.

Once that is fixed,

Reviewed-by: Anatoly Burakov <anatoly.burakov@intel.com>
diff mbox series

Patch

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;