Re: [Qemu-devel] [PATCH v3 7/7] s390x/pci: search for subregion inside the BARs

[Thomas Huth]

On 22.11.2017 23:05, Pierre Morel wrote:
> When dispatching memory access to PCI BAR region, we must
> look for possible subregions, used by the PCI device to map
> different memory areas inside the same PCI BAR.
> 
> Since the data offset we received is calculated starting at the
> region start address we need to adjust the offset for the subregion.
> 
> The data offset inside the subregion is calculated by substracting
> the subregion's starting address from the data offset in the region.
> 
> The access to the MSIX region is now handled in a generic way,
> we do not need the specific trap_msix() function anymore.
> 
> Signed-off-by: Pierre Morel <address@hidden>
> Reviewed-by: Yi Min Zhao <address@hidden>
> ---
>  hw/s390x/s390-pci-inst.c | 44 +++++++++++++++++++++++++-------------------
>  1 file changed, 25 insertions(+), 19 deletions(-)
> 
> diff --git a/hw/s390x/s390-pci-inst.c b/hw/s390x/s390-pci-inst.c
> index 8d35f8f..fae3ef7 100644
> --- a/hw/s390x/s390-pci-inst.c
> +++ b/hw/s390x/s390-pci-inst.c
> @@ -345,12 +345,31 @@ static int zpci_endian_swap(uint64_t *ptr, uint8_t len)
>      return 0;
>  }
>  
> +static MemoryRegion *s390_get_subregion(MemoryRegion *mr, uint64_t offset,
> +                                        uint8_t len)
> +{
> +    MemoryRegion *other;

Just my personal taste, but I'd rather call it "submr" or something similar.

> +    uint64_t subregion_size;
> +
> +    QTAILQ_FOREACH(other, &mr->subregions, subregions_link) {
> +        subregion_size = int128_get64(other->size);
> +        if ((offset >= other->addr) &&
> +            (offset + len) <= (other->addr + subregion_size)) {

(Too much parentheses for my taste ;-))

> +            mr = other;
> +            break;
> +        }
> +    }
> +    return mr;
> +}
> +
>  static MemTxResult zpci_read_bar(S390PCIBusDevice *pbdev, uint8_t pcias,
>                                   uint64_t offset, uint64_t *data, uint8_t 
> len)
>  {
>      MemoryRegion *mr;
>  
>      mr = pbdev->pdev->io_regions[pcias].memory;
> +    mr = s390_get_subregion(mr, offset, len);
> +    offset -= mr->addr;

I'm not that familiar with the MemoryRegion nesting ... So may I ask: Is
that "offset -= mr->addr" also right if mr does *not* point to a
sub-region, but to the main memory region? (I.e. is mr->addr == 0 in
that case?)

>      return memory_region_dispatch_read(mr, offset, data, len,
>                                         MEMTXATTRS_UNSPECIFIED);
>  }
> @@ -442,30 +461,14 @@ int pcilg_service_call(S390CPU *cpu, uint8_t r1, 
> uint8_t r2)
>      return 0;
>  }
>  
> -static int trap_msix(S390PCIBusDevice *pbdev, uint64_t offset, uint8_t pcias)
> -{
> -    if (pbdev->msix.available && pbdev->msix.table_bar == pcias &&
> -        offset >= pbdev->msix.table_offset &&
> -        offset < (pbdev->msix.table_offset +
> -                  pbdev->msix.entries * PCI_MSIX_ENTRY_SIZE)) {
> -        return 1;
> -    } else {
> -        return 0;
> -    }
> -}
> -
>  static MemTxResult zpci_write_bar(S390PCIBusDevice *pbdev, uint8_t pcias,
>                                    uint64_t offset, uint64_t data, uint8_t 
> len)
>  {
>      MemoryRegion *mr;
>  
> -    if (trap_msix(pbdev, offset, pcias)) {
> -        offset = offset - pbdev->msix.table_offset;
> -        mr = &pbdev->pdev->msix_table_mmio;
> -    } else {
> -        mr = pbdev->pdev->io_regions[pcias].memory;
> -    }
> -
> +    mr = pbdev->pdev->io_regions[pcias].memory;
> +    mr = s390_get_subregion(mr, offset, len);
> +    offset -= mr->addr;
>      return memory_region_dispatch_write(mr, offset, data, len,
>                                          MEMTXATTRS_UNSPECIFIED);
>  }
> @@ -726,6 +729,9 @@ int pcistb_service_call(S390CPU *cpu, uint8_t r1, uint8_t 
> r3, uint64_t gaddr,
>      }
>  
>      mr = pbdev->pdev->io_regions[pcias].memory;

Since this above line is done right before all calls to
s390_get_subregion(), you could maybe move it into that function, too.
(and rather call the function sth. like pci_mem_get_subregion() instead?)

> +    mr = s390_get_subregion(mr, offset, len);
> +    offset -= mr->addr;
> +
>      if (!memory_region_access_valid(mr, offset, len, true)) {
>          program_interrupt(env, PGM_OPERAND, 6);
>          return 0;
> 

 Thomas