Re: [Qemu-devel] [PATCH V3 1/2] hw/pci: reserve IO and mem for pci-2-pci bridges with no devices attached

[Michael S. Tsirkin]

On Thu, Apr 10, 2014 at 04:29:40PM +0300, Marcel Apfelbaum wrote:
> If a pci-2-pci bridge supports hot-plug functionality but there are no devices
> connected to it, reserve IO/mem in order to be able to attach devices
> later. Do not waste space, use minimum allowed.
> 
> Signed-off-by: Marcel Apfelbaum <address@hidden>

Looks good to me
Reviewed-by: Michael S. Tsirkin <address@hidden>

but let's apply with patch 2 (after it's fixed): otherwise
there's no way for hypervisors to avoid wasting resources
unnecessaily on bridges.

> ---
>  src/fw/pciinit.c |  3 +++
>  src/hw/pci.c     | 19 +++++++++++++++++++
>  src/hw/pci.h     |  1 +
>  3 files changed, 23 insertions(+)
> 
> diff --git a/src/fw/pciinit.c b/src/fw/pciinit.c
> index 64f1d41..9b5d7ad 100644
> --- a/src/fw/pciinit.c
> +++ b/src/fw/pciinit.c
> @@ -677,12 +677,15 @@ static int pci_bios_check_devices(struct pci_bus 
> *busses)
>              continue;
>          struct pci_bus *parent = &busses[pci_bdf_to_bus(s->bus_dev->bdf)];
>          int type;
> +        u8 shpc_cap = pci_find_capability(s->bus_dev, PCI_CAP_ID_SHPC);
>          for (type = 0; type < PCI_REGION_TYPE_COUNT; type++) {
>              u64 align = (type == PCI_REGION_TYPE_IO) ?
>                  PCI_BRIDGE_IO_MIN : PCI_BRIDGE_MEM_MIN;
>              if (pci_region_align(&s->r[type]) > align)
>                   align = pci_region_align(&s->r[type]);
>              u64 sum = pci_region_sum(&s->r[type]);
> +            if (!sum && shpc_cap)
> +                sum = align; /* reserve min size for hot-plug */
>              u64 size = ALIGN(sum, align);
>              int is64 = pci_bios_bridge_region_is64(&s->r[type],
>                                              s->bus_dev, type);
> diff --git a/src/hw/pci.c b/src/hw/pci.c
> index caf9265..055353d 100644
> --- a/src/hw/pci.c
> +++ b/src/hw/pci.c
> @@ -225,6 +225,25 @@ pci_find_init_device(const struct pci_device_id *ids, 
> void *arg)
>      return NULL;
>  }
>  
> +u8 pci_find_capability(struct pci_device *pci, u8 cap_id)
> +{
> +    int i;
> +    u8 cap;
> +    u16 status = pci_config_readw(pci->bdf, PCI_STATUS);
> +
> +    if (!(status & PCI_STATUS_CAP_LIST))
> +        return 0;
> +
> +    for (i = 0, cap = pci_config_readb(pci->bdf, PCI_CAPABILITY_LIST);
> +         (i <= 0xff) && cap;
> +         i++, cap = pci_config_readb(pci->bdf, cap + PCI_CAP_LIST_NEXT))
> +        if (pci_config_readb(pci->bdf, cap + PCI_CAP_LIST_ID) == cap_id)
> +            return cap;
> +
> +    return 0;
> +}
> +
> +
>  void
>  pci_reboot(void)
>  {
> diff --git a/src/hw/pci.h b/src/hw/pci.h
> index 167a027..e828225 100644
> --- a/src/hw/pci.h
> +++ b/src/hw/pci.h
> @@ -116,6 +116,7 @@ int pci_init_device(const struct pci_device_id *ids
>                      , struct pci_device *pci, void *arg);
>  struct pci_device *pci_find_init_device(const struct pci_device_id *ids
>                                          , void *arg);
> +u8 pci_find_capability(struct pci_device *pci, u8 cap_id);
>  void pci_reboot(void);
>  
>  #endif
> -- 
> 1.8.3.1