When the size of the physical address space is known (PhysBits is not
zero) move the 64bit pci io window to the end of the address space.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 src/fw/pciinit.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/fw/pciinit.c b/src/fw/pciinit.c
index badf13d3233b..ad6def93633b 100644
--- a/src/fw/pciinit.c
+++ b/src/fw/pciinit.c
@@ -1128,6 +1128,14 @@ static void pci_bios_map_devices(struct pci_bus *busses)
         r64_mem.base = le64_to_cpu(romfile_loadint("etc/reserved-memory-end", 0));
         if (r64_mem.base < 0x100000000LL + RamSizeOver4G)
             r64_mem.base = 0x100000000LL + RamSizeOver4G;
+        if (PhysBits) {
+            u64 top = 1LL << PhysBits;
+            u64 size = (ALIGN(sum_mem, (1LL<<30)) +
+                        ALIGN(sum_pref, (1LL<<30)));
+            if (r64_mem.base < top - size) {
+                r64_mem.base = top - size;
+            }
+        }
         r64_mem.base = ALIGN(r64_mem.base, align_mem);
         r64_mem.base = ALIGN(r64_mem.base, (1LL<<30));    // 1G hugepage
         r64_pref.base = r64_mem.base + sum_mem;
-- 
2.38.1

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Dear Gerd,


Thank you for the patch.

Am 21.11.22 um 11:32 schrieb Gerd Hoffmann:
> When the size of the physical address space is known (PhysBits is not
> zero) move the 64bit pci io window to the end of the address space.

It’d be great, if you elaborated, why this is an improvement.


Kind regards,

Paul


> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>   src/fw/pciinit.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/src/fw/pciinit.c b/src/fw/pciinit.c
> index badf13d3233b..ad6def93633b 100644
> --- a/src/fw/pciinit.c
> +++ b/src/fw/pciinit.c
> @@ -1128,6 +1128,14 @@ static void pci_bios_map_devices(struct pci_bus *busses)
>           r64_mem.base = le64_to_cpu(romfile_loadint("etc/reserved-memory-end", 0));
>           if (r64_mem.base < 0x100000000LL + RamSizeOver4G)
>               r64_mem.base = 0x100000000LL + RamSizeOver4G;
> +        if (PhysBits) {
> +            u64 top = 1LL << PhysBits;
> +            u64 size = (ALIGN(sum_mem, (1LL<<30)) +
> +                        ALIGN(sum_pref, (1LL<<30)));
> +            if (r64_mem.base < top - size) {
> +                r64_mem.base = top - size;
> +            }
> +        }
>           r64_mem.base = ALIGN(r64_mem.base, align_mem);
>           r64_mem.base = ALIGN(r64_mem.base, (1LL<<30));    // 1G hugepage
>           r64_pref.base = r64_mem.base + sum_mem;

On Mon, Nov 21, 2022 at 11:57:35AM +0100, Paul Menzel wrote:
> Dear Gerd,
> 
> 
> Thank you for the patch.
> 
> Am 21.11.22 um 11:32 schrieb Gerd Hoffmann:
> > When the size of the physical address space is known (PhysBits is not
> > zero) move the 64bit pci io window to the end of the address space.
> 
> It’d be great, if you elaborated, why this is an improvement.

It makes seabios follow a common pattern.  real mode address space
has io resources mapped high (below 1M).  32-bit address space has
io resources mapped high too (below 4G).  This does the same for
64-bit resources.

Physical hardware does simliar things, here is my workstation:

    # sudo cat /proc/iomem 
    [ ... regions below 4G snipped ... ]
    100000000-a36ffffff : System RAM
      2e6000000-2e7002607 : Kernel code
      2e7200000-2e7e84fff : Kernel rodata
      2e8000000-2e8326e7f : Kernel data
      2e8b6e000-2e8ffffff : Kernel bss
    a37000000-a37ffffff : RAM buffer
    2000000000-2fffffffff : PCI Bus 0000:00
      2ffff00000-2ffff0ffff : 0000:00:1f.3
      2ffff10000-2ffff1ffff : 0000:00:14.0
        2ffff10000-2ffff1ffff : xhci-hcd
      2ffff20000-2ffff23fff : 0000:00:1f.3
        2ffff20000-2ffff23fff : ICH HD audio
      2ffff24000-2ffff240ff : 0000:00:1f.4
      2ffff25000-2ffff25fff : 0000:00:16.0
        2ffff25000-2ffff25fff : mei_me

There is a larger gap between the end of memory and start of the pci io
window.  It's not the end of the *cpu* physical address space (that
would be 7fffffffff aka phys-bits=39).  Maybe there are additional
constrains in the io chipset (which is a non-issue for virtual
machines).

take care,
  Gerd

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