Re: [dpdk-dev] [PATCH v2 6/7] virtio: fix pci accesses for ppc64 in legacy mode

["Chao Zhu" <chaozhu@linux.vnet.ibm.com>]

Olivier,

Thanks for the patches! 
Just one comment:
POWER8 machine only supports little endian OS on bare metal. In VM guest, it
can support both little endian and big endian OS. Did you try to run it on
both host (little endian) and guest (big endian and little endian)?

-----Original Message-----
From: Olivier Matz [mailto:olivier.matz@6wind.com] 
Sent: 2016年5月17日 18:00
To: dev@dpdk.org
Cc: david.marchand@6wind.com; chaozhu@linux.vnet.ibm.com; yuanhan.liu@linux.
intel.com; huawei.xie@intel.com
Subject: [PATCH v2 6/7] virtio: fix pci accesses for ppc64 in legacy mode

From: David Marchand <david.marchand@6wind.com>

Although ppc supports both endianesses, qemu supposes that the cpu is big
endian and enforces this for the virtio-net stuff.

Fix PCI accesses in legacy mode. Only ppc64le is supported at the moment.

Signed-off-by: David Marchand <david.marchand@6wind.com>
Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
---
 drivers/net/virtio/virtio_pci.c | 68
+++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/drivers/net/virtio/virtio_pci.c
b/drivers/net/virtio/virtio_pci.c index 9cdca06..ebf4cf7 100644
--- a/drivers/net/virtio/virtio_pci.c
+++ b/drivers/net/virtio/virtio_pci.c
@@ -55,20 +55,88 @@
  */
 #define VIRTIO_PCI_CONFIG(hw) (((hw)->use_msix) ? 24 : 20)

+/*
+ * Since we are in legacy mode:
+ * http://ozlabs.org/~rusty/virtio-spec/virtio-0.9.5.pdf
+ *
+ * "Note that this is possible because while the virtio header is PCI (i.e.
+ * little) endian, the device-specific region is encoded in the native 
+endian of
+ * the guest (where such distinction is applicable)."
+ *
+ * For powerpc which supports both, qemu supposes that cpu is big 
+endian and
+ * enforces this for the virtio-net stuff.
+ */
+
 static void
 legacy_read_dev_config(struct virtio_hw *hw, size_t offset,
 		       void *dst, int length)
 {
+#ifdef RTE_ARCH_PPC_64
+	int size;
+
+	while (length > 0) {
+		if (length >= 4) {
+			size = 4;
+			rte_eal_pci_ioport_read(&hw->io, dst, size,
+				VIRTIO_PCI_CONFIG(hw) + offset);
+			*(uint32_t *)dst = rte_be_to_cpu_32(*(uint32_t
*)dst);
+		} else if (length >= 2) {
+			size = 2;
+			rte_eal_pci_ioport_read(&hw->io, dst, size,
+				VIRTIO_PCI_CONFIG(hw) + offset);
+			*(uint16_t *)dst = rte_be_to_cpu_16(*(uint16_t
*)dst);
+		} else {
+			size = 1;
+			rte_eal_pci_ioport_read(&hw->io, dst, size,
+				VIRTIO_PCI_CONFIG(hw) + offset);
+		}
+
+		dst = (char *)dst + size;
+		offset += size;
+		length -= size;
+	}
+#else
 	rte_eal_pci_ioport_read(&hw->io, dst, length,
 				VIRTIO_PCI_CONFIG(hw) + offset);
+#endif
 }

 static void
 legacy_write_dev_config(struct virtio_hw *hw, size_t offset,
 			const void *src, int length)
 {
+#ifdef RTE_ARCH_PPC_64
+	union {
+		uint32_t u32;
+		uint16_t u16;
+	} tmp;
+	int size;
+
+	while (length > 0) {
+		if (length >= 4) {
+			size = 4;
+			tmp.u32 = rte_cpu_to_be_32(*(const uint32_t *)src);
+			rte_eal_pci_ioport_write(&hw->io, &tmp.u32, size,
+				VIRTIO_PCI_CONFIG(hw) + offset);
+		} else if (length >= 2) {
+			size = 2;
+			tmp.u16 = rte_cpu_to_be_16(*(const uint16_t *)src);
+			rte_eal_pci_ioport_write(&hw->io, &tmp.u16, size,
+				VIRTIO_PCI_CONFIG(hw) + offset);
+		} else {
+			size = 1;
+			rte_eal_pci_ioport_write(&hw->io, src, size,
+				VIRTIO_PCI_CONFIG(hw) + offset);
+		}
+
+		src = (const char *)src + size;
+		offset += size;
+		length -= size;
+	}
+#else
 	rte_eal_pci_ioport_write(&hw->io, src, length,
 				 VIRTIO_PCI_CONFIG(hw) + offset);
+#endif
 }

 static uint64_t
--
2.8.0.rc3