On Thu, Mar 21, 2013 at 06:59:33PM +1030, Rusty Russell wrote:
> Another HPA suggestion: that the device be allowed to offer duplicate
> capabilities, particularly so it can offer a mem and an I/O bar and let
> the guest decide (Linux guest probably doesn't care?).
>
> Cc: H. Peter Anvin <hpa@xxxxxxxxx>
> Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
I think guests is exactly the wrong place to decide,
it really does not know whether it's running on a
hypervisor with fast IO or fast memory.
Also, as long as we have an IO BAR, we have problems allocating it.
So I think we don't need this, see my suggestion
about fixed IO addresses instead.
> ---
> drivers/virtio/virtio_pci_legacy.c | 3 ++-
> include/linux/virtio_pci.h | 20 ++++++++++++++++----
> 2 files changed, 18 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/virtio/virtio_pci_legacy.c b/drivers/virtio/virtio_pci_legacy.c
> index 501fa79..c7aadcb 100644
> --- a/drivers/virtio/virtio_pci_legacy.c
> +++ b/drivers/virtio/virtio_pci_legacy.c
> @@ -728,7 +728,8 @@ static int virtio_pci_probe(struct pci_dev *pci_dev,
> }
>
> /* We leave modern virtio-pci for the modern driver. */
> - cap = virtio_pci_find_capability(pci_dev, VIRTIO_PCI_CAP_COMMON_CFG);
> + cap = virtio_pci_find_capability(pci_dev, VIRTIO_PCI_CAP_COMMON_CFG,
> + IORESOURCE_IO|IORESOURCE_MEM);
> if (cap) {
> if (force_nonlegacy)
> dev_info(&pci_dev->dev,
> diff --git a/include/linux/virtio_pci.h b/include/linux/virtio_pci.h
> index 2714160..6d2816b 100644
> --- a/include/linux/virtio_pci.h
> +++ b/include/linux/virtio_pci.h
> @@ -4,18 +4,30 @@
> #define VIRTIO_PCI_NO_LEGACY
> #include <uapi/linux/virtio_pci.h>
>
> -/* Returns offset of the capability, or 0. */
> -static inline int virtio_pci_find_capability(struct pci_dev *dev, u8 cfg_type)
> +/**
> + * virtio_pci_find_capability - walk capabilities to find device info.
> + * @dev: the pci device
> + * @cfg_type: the VIRTIO_PCI_CAP_* value we seek
> + * @ioresource_types: IORESOURCE_MEM and/or IORESOURCE_IO.
> + *
> + * Returns offset of the capability, or 0.
> + */
> +static inline int virtio_pci_find_capability(struct pci_dev *dev, u8 cfg_type,
> + u32 ioresource_types)
> {
> int pos;
>
> for (pos = pci_find_capability(dev, PCI_CAP_ID_VNDR);
> pos > 0;
> pos = pci_find_next_capability(dev, pos, PCI_CAP_ID_VNDR)) {
> - u8 type;
> + u8 type, bar;
> pci_read_config_byte(dev, pos + offsetof(struct virtio_pci_cap,
> cfg_type), &type);
> - if (type == cfg_type)
> + if (type != cfg_type)
> + continue;
> + pci_read_config_byte(dev, pos + offsetof(struct virtio_pci_cap,
> + bar), &bar);
> + if (pci_resource_flags(dev, bar) & ioresource_types)
> return pos;
> }
> return 0;
> --
> 1.7.10.4
>
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