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

[Alex Williamson <alex.williamson@redhat.com>]

On Thu, 2010-10-28 at 17:00 +0200, Avi Kivity wrote:
> On 10/23/2010 06:55 PM, Alex Williamson wrote:
> > On Sat, 2010-10-23 at 18:18 +0200, Michael S. Tsirkin wrote:
> > >  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.
> >
> > That's true, but I was hoping to save that for later since we don't seem
> > to be running into that problem yet.  Current device assignment code
> > assumes a single page, and I haven't heard of anyone with a vector table
> > that exceeds that yet.  Thanks,
> >
> 
> Ok; applied.  Please add some warning if the condition happens so the 
> breakage is at least not silent.

Looks like this is already handled before we even get here.  msix_init()
checks nentries against the max supported in a single page and returns
-EINVAL if over.  So I think we're safely covered until we add support
for more pages.  Thanks,

Alex