Re: [Qemu-devel] [RE-RESEND PATCH] pci: Adjust PCI config limit based on bus topology

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

On Wed, Feb 17, 2016 at 01:28:12PM -0700, Alex Williamson wrote:
> 
> Hi Michael,
> 
> Would you like me to send this for a 4th time or are you OK with me
> pulling this through my tree with Marcel's R-b?  Thanks,
> 
> Alex

Sorry, keep forgetting about it.

> 
> On Mon, 18 Jan 2016 16:06:03 -0700
> Alex Williamson <alex.williamson@redhat.com> wrote:
> 
> > A conventional PCI bus does not support config space accesses above
> > the standard 256 byte configuration space.  PCIe-to-PCI bridges are
> > not permitted to forward transactions if the extended register address
> > field is non-zero and must handle it as an unsupported request (PCIe
> > bridge spec rev 1.0, 4.1.3, 4.1.4).  Therefore, we should not support
> > extended config space if there is a conventional bus anywhere on the
> > path to a device.
> > 
> > Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> > ---
> > Previous postings:
> > https://lists.gnu.org/archive/html/qemu-devel/2015-10/msg05384.html
> > https://lists.gnu.org/archive/html/qemu-devel/2015-11/msg02422.html
> > 
> >  hw/pci/pci_host.c |   26 ++++++++++++++++++++++++++
> >  1 file changed, 26 insertions(+)
> > 
> > diff --git a/hw/pci/pci_host.c b/hw/pci/pci_host.c
> > index 49f59a5..3a3e294 100644
> > --- a/hw/pci/pci_host.c
> > +++ b/hw/pci/pci_host.c
> > @@ -19,6 +19,7 @@
> >   */
> >  
> >  #include "hw/pci/pci.h"
> > +#include "hw/pci/pci_bridge.h"
> >  #include "hw/pci/pci_host.h"
> >  #include "hw/pci/pci_bus.h"
> >  #include "trace.h"
> > @@ -49,9 +50,29 @@ static inline PCIDevice *pci_dev_find_by_addr(PCIBus *bus, uint32_t addr)
> >      return pci_find_device(bus, bus_num, devfn);
> >  }
> >  
> > +static void pci_adjust_config_limit(PCIBus *bus, uint32_t *limit)
> > +{
> > +    if (*limit > PCI_CONFIG_SPACE_SIZE) {
> > +        if (!pci_bus_is_express(bus)) {
> > +            *limit = PCI_CONFIG_SPACE_SIZE;
> > +            return;
> > +        }
> > +
> > +        if (!pci_bus_is_root(bus)) {
> > +            PCIDevice *bridge = pci_bridge_get_device(bus);
> > +            pci_adjust_config_limit(bridge->bus, limit);
> > +        }
> > +    }
> > +}
> > +
> >  void pci_host_config_write_common(PCIDevice *pci_dev, uint32_t addr,
> >                                    uint32_t limit, uint32_t val, uint32_t len)
> >  {
> > +    pci_adjust_config_limit(pci_dev->bus, &limit);
> > +    if (limit <= addr) {
> > +        return;
> > +    }
> > +
> >      assert(len <= 4);
> >      /* non-zero functions are only exposed when function 0 is present,
> >       * allowing direct removal of unexposed functions.
> > @@ -70,6 +91,11 @@ uint32_t pci_host_config_read_common(PCIDevice *pci_dev, uint32_t addr,
> >  {
> >      uint32_t ret;
> >  
> > +    pci_adjust_config_limit(pci_dev->bus, &limit);
> > +    if (limit <= addr) {
> > +        return ~0x0;
> > +    }
> > +
> >      assert(len <= 4);
> >      /* non-zero functions are only exposed when function 0 is present,
> >       * allowing direct removal of unexposed functions.
> > 

It's kind of nasty that we do it on each access ...
How about storing the size in device itself?

-- 
MST