[Qemu-devel] Re: [PATCH 1/2] msix: Allow msix_init on a device with existing MSI-X capability

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Oct 22, 2010 at 02:40:31PM -0600, Alex Williamson wrote:
> To enable common msix support to be used with pass through devices,
> don't attempt to change the BAR if the device already has an
> MSI-X capability.  This also means we want to pay closer attention
> to the size when we map the msix table page, as it isn't necessarily
> covering the entire end of the BAR.
> 
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
> 
>  hw/msix.c |   67 +++++++++++++++++++++++++++++++++++--------------------------
>  1 files changed, 38 insertions(+), 29 deletions(-)
> 
> diff --git a/hw/msix.c b/hw/msix.c
> index 43efbd2..4122395 100644
> --- a/hw/msix.c
> +++ b/hw/msix.c
> @@ -167,35 +167,43 @@ static int msix_add_config(struct PCIDevice *pdev, unsigned short nentries,
>  {
>      int config_offset;
>      uint8_t *config;
> -    uint32_t new_size;
>  
> -    if (nentries < 1 || nentries > PCI_MSIX_FLAGS_QSIZE + 1)
> -        return -EINVAL;
> -    if (bar_size > 0x80000000)
> -        return -ENOSPC;
> -
> -    /* Add space for MSI-X structures */
> -    if (!bar_size) {
> -        new_size = MSIX_PAGE_SIZE;
> -    } else if (bar_size < MSIX_PAGE_SIZE) {
> -        bar_size = MSIX_PAGE_SIZE;
> -        new_size = MSIX_PAGE_SIZE * 2;
> -    } else {
> -        new_size = bar_size * 2;
> -    }
> -
> -    pdev->msix_bar_size = new_size;
> -    config_offset = pci_add_capability(pdev, PCI_CAP_ID_MSIX, MSIX_CAP_LENGTH);
> -    if (config_offset < 0)
> -        return config_offset;
> -    config = pdev->config + config_offset;
> -
> -    pci_set_word(config + PCI_MSIX_FLAGS, nentries - 1);
> -    /* Table on top of BAR */
> -    pci_set_long(config + MSIX_TABLE_OFFSET, bar_size | bar_nr);
> -    /* Pending bits on top of that */
> -    pci_set_long(config + MSIX_PBA_OFFSET, (bar_size + MSIX_PAGE_PENDING) |
> -                 bar_nr);
> +    pdev->msix_bar_size = bar_size;
> +
> +    config_offset = pci_find_capability(pdev, PCI_CAP_ID_MSIX);
> +
> +    if (!config_offset) {
> +        uint32_t new_size;
> +
> +        if (nentries < 1 || nentries > PCI_MSIX_FLAGS_QSIZE + 1)
> +            return -EINVAL;
> +        if (bar_size > 0x80000000)
> +            return -ENOSPC;
> +
> +        /* Add space for MSI-X structures */
> +        if (!bar_size) {
> +            new_size = MSIX_PAGE_SIZE;
> +        } else if (bar_size < MSIX_PAGE_SIZE) {
> +            bar_size = MSIX_PAGE_SIZE;
> +            new_size = MSIX_PAGE_SIZE * 2;
> +        } else {
> +            new_size = bar_size * 2;
> +        }
> +
> +        pdev->msix_bar_size = new_size;
> +        config_offset = pci_add_capability(pdev, PCI_CAP_ID_MSIX,
> +                                           MSIX_CAP_LENGTH);
> +        if (config_offset < 0)
> +            return config_offset;
> +        config = pdev->config + config_offset;
> +
> +        pci_set_word(config + PCI_MSIX_FLAGS, nentries - 1);
> +        /* Table on top of BAR */
> +        pci_set_long(config + MSIX_TABLE_OFFSET, bar_size | bar_nr);
> +        /* Pending bits on top of that */
> +        pci_set_long(config + MSIX_PBA_OFFSET, (bar_size + MSIX_PAGE_PENDING) |
> +                     bar_nr);
> +    }
>      pdev->msix_cap = config_offset;
>      /* Make flags bit writeable. */
>      pdev->wmask[config_offset + MSIX_CONTROL_OFFSET] |= MSIX_ENABLE_MASK |
> @@ -337,7 +345,8 @@ void msix_mmio_map(PCIDevice *d, int region_num,
>          return;
>      if (size <= offset)
>          return;
> -    cpu_register_physical_memory(addr + offset, size - offset,
> +    cpu_register_physical_memory(addr + offset,
> +                                 MIN(size - offset, MSIX_PAGE_SIZE),

This is wrong I think, the table might not fit in a single page.
You would need to read table size out of from device config.

>                                   d->msix_mmio_index);
>  }
>