[PATCH v2 log fixed] virtio_mmio: fix endian-ness for mmio

Michael S. Tsirkin
2015-03-12T09:37:51Z

Subject: [PATCH] virtio_mmio: fix access width for mmio

Going over the virtio mmio code, I noticed that it doesn't correctly
access modern device config values using "natural" accessors: it uses
readb to get/set them byte by byte, while the virtio 1.0 spec explicitly states:

4.2.2.2 Driver Requirements: MMIO Device Register Layout

...

The driver MUST only use 32 bit wide and aligned reads and writes to
access the control registers described in table 4.1.
For the device-specific configuration space, the driver MUST use
8 bit wide accesses for 8 bit wide fields, 16 bit wide and aligned
accesses for 16 bit wide fields and 32 bit wide and aligned accesses for
32 and 64 bit wide fields.

Borrow code from virtio_pci_modern to do this correctly.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

---

This is exactly the same as PATCH virtio_mmio: fix endian-ness for mmio
but with corrected subject and commit log, to make
it easier to apply.

Note: untested: QEMU doesn't support virtio 1.0 for virtio-mmio,
but seems pretty obvious. Let's apply ASAP so we don't ship
incompliant drivers for virtio 1.0?

drivers/virtio/virtio_mmio.c | 79 +++++++++++++++++++++++++++++++++++++++-----
1 file changed, 71 insertions(+), 8 deletions(-)

diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index cad5698..0375456 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -156,22 +156,85 @@ static void vm_get(struct virtio_device *vdev, unsigned offset,
void *buf, unsigned len)
{
struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
- u8 *ptr = buf;
- int i;
+ void __iomem *base = vm_dev->base + VIRTIO_MMIO_CONFIG;
+ u8 b;
+ __le16 w;
+ __le32 l;

- for (i = 0; i < len; i++)
- ptr[i] = readb(vm_dev->base + VIRTIO_MMIO_CONFIG + offset + i);
+ if (vm_dev->version == 1) {
+ u8 *ptr = buf;
+ int i;
+
+ for (i = 0; i < len; i++)
+ ptr[i] = readb(base + offset + i);
+ return;
+ }
+
+ switch (len) {
+ case 1:
+ b = readb(base + offset);
+ memcpy(buf, &b, sizeof b);
+ break;
+ case 2:
+ w = cpu_to_le16(readw(base + offset));
+ memcpy(buf, &w, sizeof w);
+ break;
+ case 4:
+ l = cpu_to_le32(readl(base + offset));
+ memcpy(buf, &l, sizeof l);
+ break;
+ case 8:
+ l = cpu_to_le32(readl(base + offset));
+ memcpy(buf, &l, sizeof l);
+ l = cpu_to_le32(ioread32(base + offset + sizeof l));
+ memcpy(buf + sizeof l, &l, sizeof l);
+ break;
+ default:
+ BUG();
+ }
}

static void vm_set(struct virtio_device *vdev, unsigned offset,
const void *buf, unsigned len)
{
struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
- const u8 *ptr = buf;
- int i;
+ void __iomem *base = vm_dev->base + VIRTIO_MMIO_CONFIG;
+ u8 b;
+ __le16 w;
+ __le32 l;

- for (i = 0; i < len; i++)
- writeb(ptr[i], vm_dev->base + VIRTIO_MMIO_CONFIG + offset + i);
+ if (vm_dev->version == 1) {
+ const u8 *ptr = buf;
+ int i;
+
+ for (i = 0; i < len; i++)
+ writeb(ptr[i], base + offset + i);
+
+ return;
+ }
+
+ switch (len) {
+ case 1:
+ memcpy(&b, buf, sizeof b);
+ writeb(b, base + offset);
+ break;
+ case 2:
+ memcpy(&w, buf, sizeof w);
+ writew(le16_to_cpu(w), base + offset);
+ break;
+ case 4:
+ memcpy(&l, buf, sizeof l);
+ writel(le32_to_cpu(l), base + offset);
+ break;
+ case 8:
+ memcpy(&l, buf, sizeof l);
+ writel(le32_to_cpu(l), base + offset);
+ memcpy(&l, buf + sizeof l, sizeof l);
+ writel(le32_to_cpu(l), base + offset + sizeof l);
+ break;
+ default:
+ BUG();
+ }
}

static u8 vm_get_status(struct virtio_device *vdev)
--
MST