Re: [PATCH 3/5] hw/pci-host/prep: Remove unuseful memory region mapping

[Peter Xu]

On Fri, Mar 12, 2021 at 07:28:49PM +0100, Philippe Mathieu-Daudé wrote:
> The pci_io_non_contiguous region is mapped on top of pci_io
> with higher priority, but simply dispatch into this region
> address space. Simplify by directly registering the former
> region in place, and adapt the address space dispatch offsets.
> 
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>  hw/pci-host/prep.c | 11 ++++-------
>  1 file changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/hw/pci-host/prep.c b/hw/pci-host/prep.c
> index 0a9162fba97..00a28c2d18c 100644
> --- a/hw/pci-host/prep.c
> +++ b/hw/pci-host/prep.c
> @@ -159,8 +159,7 @@ static uint64_t raven_io_read(void *opaque, hwaddr addr,
>      uint8_t buf[4];
>  
>      addr = raven_io_address(s, addr);
> -    address_space_read(&s->pci_io_as, addr + 0x80000000,
> -                       MEMTXATTRS_UNSPECIFIED, buf, size);
> +    address_space_read(&s->pci_io_as, addr, MEMTXATTRS_UNSPECIFIED, buf, 
> size);
>  
>      if (size == 1) {
>          return buf[0];
> @@ -191,8 +190,7 @@ static void raven_io_write(void *opaque, hwaddr addr,
>          g_assert_not_reached();
>      }
>  
> -    address_space_write(&s->pci_io_as, addr + 0x80000000,
> -                        MEMTXATTRS_UNSPECIFIED, buf, size);
> +    address_space_write(&s->pci_io_as, addr, MEMTXATTRS_UNSPECIFIED, buf, 
> size);

This changes access to s->pci_io_as, but below didn't change s->pci_io_as
layout at all (below is about address_space_mem).  Is this intended?

>  }
>  
>  static const MemoryRegionOps raven_io_ops = {
> @@ -294,9 +292,8 @@ static void raven_pcihost_initfn(Object *obj)
>      address_space_init(&s->pci_io_as, &s->pci_io, "raven-io");
>  
>      /* CPU address space */
> -    memory_region_add_subregion(address_space_mem, 0x80000000, &s->pci_io);
> -    memory_region_add_subregion_overlap(address_space_mem, 0x80000000,
> -                                        &s->pci_io_non_contiguous, 1);
> +    memory_region_add_subregion(address_space_mem, 0x80000000,
> +                                &s->pci_io_non_contiguous);

I don't know any of this code at all... but it seems the two memory regions are
not identical in size:

    memory_region_init(&s->pci_io, obj, "pci-io", 0x3f800000);
    memory_region_init_io(&s->pci_io_non_contiguous, obj, &raven_io_ops, s,
                          "pci-io-non-contiguous", 0x00800000);

Then it seems the memory access dispatching to (0x00800000, 0x3f800000) would
change too, from s->pci_io to nothing.  Raise this up too since I don't know
either whether it's intended..

>      memory_region_add_subregion(address_space_mem, 0xc0000000, 
> &s->pci_memory);
>      pci_root_bus_new_inplace(&s->pci_bus, sizeof(s->pci_bus), DEVICE(obj), 
> NULL,
>                               &s->pci_memory, &s->pci_io, 0, TYPE_PCI_BUS);
> -- 
> 2.26.2
> 

-- 
Peter Xu