Re: [PATCH 4/5] pci-assign: Convert need_emulate_cmd into a bitmask

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

On Tue, 2010-12-14 at 00:25 +0100, Jan Kiszka wrote:
> From: Jan Kiszka <jan.kiszka@siemens.com>
> 
> Define a mask of PCI command register bits that need to be emulated,
> i.e. read back from their shadow state. We will need this for
> selectively emulating the INTx mask bit.
> 
> Note: No initialization of emulate_cmd_mask to zero needed, the device
> state is already zero-initialized.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> ---
>  hw/device-assignment.c |   18 ++++++++++--------
>  hw/device-assignment.h |    2 +-
>  2 files changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/hw/device-assignment.c b/hw/device-assignment.c
> index ef045f4..26d3bd7 100644
> --- a/hw/device-assignment.c
> +++ b/hw/device-assignment.c
> @@ -525,14 +525,17 @@ again:
>      DEBUG("(%x.%x): address=%04x val=0x%08x len=%d\n",
>            (d->devfn >> 3) & 0x1F, (d->devfn & 0x7), address, val, len);
>  
> -    if (pci_dev->need_emulate_cmd &&
> +    if (pci_dev->emulate_cmd_mask &&
>          ranges_overlap(address, len, PCI_COMMAND, 2)) {
>          if (address == PCI_COMMAND) {
> -            val &= 0xffff0000;
> -            val |= pci_default_read_config(d, PCI_COMMAND, 2);
> +            val &= ~pci_dev->emulate_cmd_mask;
> +            val |= pci_default_read_config(d, PCI_COMMAND, 2) &
> +                        pci_dev->emulate_cmd_mask;
>          } else {
>              /* high-byte access */
> -            val = pci_default_read_config(d, PCI_COMMAND+1, 1);
> +            val &= ~(pci_dev->emulate_cmd_mask >> 8);
> +            val |= pci_default_read_config(d, PCI_COMMAND+1, 1) &
> +                        (pci_dev->emulate_cmd_mask >> 8);
>          }
>      }

We should definitely be using merge_bits here, this is the sort of thing
I had in mind for it:

val = merge_bits(val, pci_default_read_config(d, address, len), PCI_COMMAND, pci_dev->emulate_cmd_mask);

> @@ -800,10 +803,9 @@ again:
>  
>      /* dealing with virtual function device */
>      snprintf(name, sizeof(name), "%sphysfn/", dir);
> -    if (!stat(name, &statbuf))
> -	    pci_dev->need_emulate_cmd = 1;
> -    else
> -	    pci_dev->need_emulate_cmd = 0;
> +    if (!stat(name, &statbuf)) {
> +        pci_dev->emulate_cmd_mask = 0xffff;
> +    }
>  
>      dev->region_number = r;
>      return 0;
> diff --git a/hw/device-assignment.h b/hw/device-assignment.h
> index c94a730..9ead022 100644
> --- a/hw/device-assignment.h
> +++ b/hw/device-assignment.h
> @@ -109,7 +109,7 @@ typedef struct AssignedDevice {
>      void *msix_table_page;
>      target_phys_addr_t msix_table_addr;
>      int mmio_index;
> -    int need_emulate_cmd;
> +    uint32_t emulate_cmd_mask;
>      char *configfd_name;
>      QLIST_ENTRY(AssignedDevice) next;
>  } AssignedDevice;