Re: [Qemu-devel] [PATCH] msix: Support specifying offsets, BARs, and capability location

[Alex Williamson]

On Wed, 2012-06-13 at 12:44 +0200, Jan Kiszka wrote:
> On 2012-06-12 22:03, Alex Williamson wrote:
> > msix_init has very little configurability as to how it lays out MSIX
> > for a device.  It claims to resize BARs, but doesn't actually do this
> > anymore.  This patch allows MSIX to be fully specified, which is
> > necessary both for emulated devices trying to match the physical
> > layout of a hardware device as well as for any kind of device
> > assignment.
> > 
> > New functions msix_init_bar & msix_uninit_bar provide wrappers around
> > the more detailed functions for drivers that just want a simple MSIX
> > setup.
> > 
> > Signed-off-by: Alex Williamson <address@hidden>
> > ---
> > 
> >  hw/ivshmem.c    |    9 +-
> >  hw/msix.c       |  299 
> > +++++++++++++++++++++++++++++++------------------------
> >  hw/msix.h       |   11 +-
> >  hw/pci.h        |   12 ++
> >  hw/virtio-pci.c |   15 +--
> >  5 files changed, 192 insertions(+), 154 deletions(-)
> > 
> > diff --git a/hw/ivshmem.c b/hw/ivshmem.c
> > index 05559b6..71c84a6 100644
> > --- a/hw/ivshmem.c
> > +++ b/hw/ivshmem.c
> > @@ -563,16 +563,13 @@ static uint64_t ivshmem_get_size(IVShmemState * s) {
> > 
> >  static void ivshmem_setup_msi(IVShmemState * s)
> >  {
> > -    memory_region_init(&s->msix_bar, "ivshmem-msix", 4096);
> > -    if (!msix_init(&s->dev, s->vectors, &s->msix_bar, 1, 0)) {
> > -        pci_register_bar(&s->dev, 1, PCI_BASE_ADDRESS_SPACE_MEMORY,
> > -                         &s->msix_bar);
> > -        IVSHMEM_DPRINTF("msix initialized (%d vectors)\n", s->vectors);
> > -    } else {
> > +    if (msix_init_bar(&s->dev, s->vectors, &s->msix_bar, 1, 
> > "ivshmem-msix")) {
> 
> I don't think the callers of msix_init_bar should have to provide the
> memory region for that bar. That can be embedded into PCIDevice, just
> like you did for the table and PBA. That was my idea with msix_init_simple.

If it's embedded on PCIDevice, then there are questions around whether
drivers using msix_init should use that MemoryRegion for their BAR, then
if we have the MemoryRegion for one BAR embedded in PCIDevice, why not
all of them?  It seems imperfect either way.

> Back then, I only included a generic memory region name. That can be
> improved, but without bothering the caller. Just derive it from
> PCIDevice::name.

Sure, I can move the name into msix_init_bar().  Thanks,

Alex