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

Rusty Russell
2015-03-13T01:29:19Z

"Michael S. Tsirkin" <mst@redhat.com> writes:
> Subject: [PATCH] virtio_mmio: fix access width for mmio

Just for the record:

Applied.

Thanks,
Rusty.

> 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