[PATCH 1/1] OvmfPkg/PciHotPlugInitDxe: fix io window size

["Gerd Hoffmann" <kraxel@redhat.com>]

Smallest IO window size for PCI bridges is 0x1000.  Add a check and
fixup the Exponent of needed.  Avoids broken resource assignments
like this:

    [ ... ]
    PciBus: Resource Map for Root Bridge PciRoot(0x0)
    Type =   Io16; Base = 0x6000;   Length = 0x7000;        Alignment = 0xFFF
    [ ... ]
       Base = 0xC000;       Length = 0x200; Alignment = 0xFFF;      Owner = PPB [00|02|00:**]
       Base = 0xC200;       Length = 0x40;  Alignment = 0x3F;       Owner = PCI [00|1F|03:20]
       Base = 0xC240;       Length = 0x20;  Alignment = 0x1F;       Owner = PCI [00|1F|02:20]
    [ ... ]

... which the linux kernel fixes up later:

    [    0.644657] pci 0000:00:1f.3: BAR 4: assigned [io  0x1000-0x103f]
    [    0.646833] pci 0000:00:1f.2: BAR 4: assigned [io  0x1040-0x105f]

With the patch applied:

    { ... ]
    PciBus: Resource Map for Root Bridge PciRoot(0x0)
    Type =   Io16; Base = 0x6000;   Length = 0x8000;        Alignment = 0xFFF
    [ ... ]
       Base = 0xC000;       Length = 0x1000;        Alignment = 0xFFF;      Owner = PPB [00|02|00:**]
       Base = 0xD000;       Length = 0x40;  Alignment = 0x3F;       Owner = PCI [00|1F|03:20]
       Base = 0xD040;       Length = 0x20;  Alignment = 0x1F;       Owner = PCI [00|1F|02:20]
    [ ... ]

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.c b/OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.c
index 3f9c84cf2b54..6c8bbc3b199d 100644
--- a/OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.c
+++ b/OvmfPkg/PciHotPlugInitDxe/PciHotPlugInit.c
@@ -117,6 +117,10 @@ SetIoPadding (
   IN     UINTN                              SizeExponent
   )
 {
+  if (SizeExponent < 12) {
+    SizeExponent = 12;
+  }
+
   Descriptor->ResType      = ACPI_ADDRESS_SPACE_TYPE_IO;
   Descriptor->AddrLen      = LShiftU64 (1, SizeExponent);
   Descriptor->AddrRangeMax = Descriptor->AddrLen - 1;
-- 
2.38.1