PCI MMIO and MTRR/PTEs

[macpacheco]

I've had zero luck testing PCI devices running on BareMetal. The symptom is whatever writes go to PCI MMIO memory is ignored, no changes at all.
So I realized, MTRR or page tables must the properly set, otherwise the CPU will think its regular memory and all kinds of strange behavior will ensue. Like the one I'm getting.
I have 2 AMD CPU/AMD chipset (one laptop, one desktop), both with RTL8168 NIC and AMD AHCI. I can't get either to work, for the same reason.
Did you tested any PCI peripherals with BM ?
PS: This issue doesn't happen with emulated hardware under QEMU. AHCI and Intel I8257x code runs just fine under QEMU.
I managed to get vfio-pci to work, and I get the same problem acessing an RTL8168 NIC from within QEMU but pass through to real hardware.

[IanSeyler]

Yes, PCI devices were tested. The AHCI and i8254x drivers were written when BareMetal only supported PCI.

I'll try to find an older system that has PCI and verify.

[IanSeyler]

Can you read the hardware registers by using peek?

[macpacheco]

Oh, I didn't mean PCI as in excluding PCIe. I meant PCI as in HPET/IOAPIC/APIC and other MMIO based peripherals that don't involve PCI/PCIe enumeration work fine.

[IanSeyler]

Ok so any PCI/PCIe devices aren't working for you. The r8169 driver uses port I/O (not MMIO) but that doesn't work for you either?