Re: [Qemu-devel] [PATCH v2 1/6] msix: Add simple BAR allocation MSIX setup functions

[Michael S. Tsirkin]

On Thu, Jun 14, 2012 at 06:11:18PM +0200, Jan Kiszka wrote:
> On 2012-06-14 18:05, Michael S. Tsirkin wrote:
> > On Thu, Jun 14, 2012 at 05:55:18PM +0200, Jan Kiszka wrote:
> >> On 2012-06-14 17:49, Michael S. Tsirkin wrote:
> >>> On Wed, Jun 13, 2012 at 10:51:19PM -0600, Alex Williamson wrote:
> >>>> msi_init() takes over a BAR without really specifying or allowing
> >>>> specification of how it does so.  Instead, let's split it into
> >>>> two interfaces, one fully specified, and one trivially easy.  This
> >>>> implements the latter.  msix_init_exclusive_bar() takes over
> >>>> allocating and filling a PCI BAR _exclusively_ for the use of MSIX.
> >>>> When used, the matching msi_uninit_exclusive_bar() should be used
> >>>> to tear it down.
> >>>>
> >>>> Signed-off-by: Alex Williamson <address@hidden>
> >>>> ---
> >>>>
> >>>>  hw/msix.c |   43 +++++++++++++++++++++++++++++++++++++++++++
> >>>>  hw/msix.h |    3 +++
> >>>>  hw/pci.h  |    2 ++
> >>>>  3 files changed, 48 insertions(+)
> >>>>
> >>>> diff --git a/hw/msix.c b/hw/msix.c
> >>>> index b64f109..a4cdfb0 100644
> >>>> --- a/hw/msix.c
> >>>> +++ b/hw/msix.c
> >>>> @@ -299,6 +299,41 @@ err_config:
> >>>>      return ret;
> >>>>  }
> >>>>  
> >>>> +int msix_init_exclusive_bar(PCIDevice *dev, unsigned short nentries,
> >>>> +                            uint8_t bar_nr)
> >>>> +{
> >>>> +    int ret;
> >>>> +    char *name;
> >>>> +
> >>>> +    /*
> >>>> +     * Migration compatibility dictates that this remains a 4k
> >>>> +     * BAR with the vector table in the lower half and PBA in
> >>>> +     * the upper half.
> >>>> +     */
> >>>> +    if (nentries * PCI_MSIX_ENTRY_SIZE > 2048) {
> >>>> +        return -EINVAL;
> >>>> +    }
> >>>> +
> >>>> +    if (asprintf(&name, "%s MSIX BAR", dev->name) == -1) {
> >>>> +        return -ENOMEM;
> >>>> +    }
> >>>> +
> >>>> +    memory_region_init(&dev->msix_exclusive_bar, name, 4096);
> >>>> +
> >>>> +    free(name);
> >>>> +
> >>>> +    ret = msix_init(dev, nentries, &dev->msix_exclusive_bar, bar_nr, 
> >>>> 4096);
> >>>> +    if (ret) {
> >>>> +        memory_region_destroy(&dev->msix_exclusive_bar);
> >>>> +        return ret;
> >>>> +    }
> >>>> +
> >>>> +    pci_register_bar(dev, bar_nr, PCI_BASE_ADDRESS_SPACE_MEMORY,
> >>>> +                     &dev->msix_exclusive_bar);
> >>>> +
> >>>> +    return 0;
> >>>> +}
> >>>> +
> >>>>  static void msix_free_irq_entries(PCIDevice *dev)
> >>>>  {
> >>>>      int vector;
> >>>> @@ -329,6 +364,14 @@ int msix_uninit(PCIDevice *dev, MemoryRegion *bar)
> >>>>      return 0;
> >>>>  }
> >>>>  
> >>>> +void msix_uninit_exclusive_bar(PCIDevice *dev)
> >>>> +{
> >>>> +    if (msix_present(dev)) {
> >>>> +        msix_uninit(dev, &dev->msix_exclusive_bar);
> >>>> +        memory_region_destroy(&dev->msix_exclusive_bar);
> >>>> +    }
> >>>> +}
> >>>> +
> >>>>  void msix_save(PCIDevice *dev, QEMUFile *f)
> >>>>  {
> >>>>      unsigned n = dev->msix_entries_nr;
> >>>> diff --git a/hw/msix.h b/hw/msix.h
> >>>> index e5a488d..bed6bfb 100644
> >>>> --- a/hw/msix.h
> >>>> +++ b/hw/msix.h
> >>>> @@ -7,11 +7,14 @@
> >>>>  int msix_init(PCIDevice *pdev, unsigned short nentries,
> >>>>                MemoryRegion *bar,
> >>>>                unsigned bar_nr, unsigned bar_size);
> >>>> +int msix_init_exclusive_bar(PCIDevice *dev, unsigned short nentries,
> >>>> +                            uint8_t bar_nr);
> >>>>  
> >>>>  void msix_write_config(PCIDevice *pci_dev, uint32_t address,
> >>>>                         uint32_t val, int len);
> >>>>  
> >>>>  int msix_uninit(PCIDevice *d, MemoryRegion *bar);
> >>>> +void msix_uninit_exclusive_bar(PCIDevice *dev);
> >>>>  
> >>>>  unsigned int msix_nr_vectors_allocated(const PCIDevice *dev);
> >>>>  
> >>>> diff --git a/hw/pci.h b/hw/pci.h
> >>>> index 4c96268..d517a54 100644
> >>>> --- a/hw/pci.h
> >>>> +++ b/hw/pci.h
> >>>> @@ -226,6 +226,8 @@ struct PCIDevice {
> >>>>  
> >>>>      /* Space to store MSIX table */
> >>>>      uint8_t *msix_table_page;
> >>>> +    /* MemoryRegion container for msix exclusive BAR setup */
> >>>> +    MemoryRegion msix_exclusive_bar;
> >>>
> >>> Wrappers are good but this doesn't belong in PCIDevice IMO.
> >>> E.g. when I debug and look at data structure I don't want to dig into
> >>> code and go "oh this device uses an exclusive bar to it's here, that one
> >>> uses a non exlcusive so the field is invalid, the real bar is over
> >>> there.
> >>>
> >>> Keep the region in devices where it was, pass to msix_init_exclusive_bar
> >>> by parameter.
> >>
> >> I disagree. There are plenty of fields in PCIDevice that are only used
> >> under certain circumstances. This is just +1, and it makes the interface
> >> usage much easier.
> >>
> >> Jan
> > 
> > *Much* easier? It's one parameter less.
> 
> ...and one field to add to every user of msix_init_exclusive_bar while
> those users have no business with it. The container is a pure internal
> field, so it belongs to the infrastructure.
> 
> Jan

True. I wish I had a better idea. Will ponder this a bit.

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