Hi all, As part of testing my OpenBIOS virtio-blk implementation, I've been trying to use it under the 40p machine and have some questions related to how address spaces are interpreted.
The 40p PCI address space is aliased onto the CPU physical address space with an offset of 0x80000000 i.e. PCI address space 0x80001234 -> CPU address space 0x1234 For the LSI SCSI controller this just works: when configuring the DMA descriptors I write the destination address to the LSI registers in PCI address space i.e. 0x80001234. Internally this calls pci_dma_read() and pci_dma_write() and the data gets transferred correctly to physical address 0x1234. When trying to configure a virtio device I'm not seeing the same behaviour: firstly it seems that I need to write the CPU address 0x1234 to VIRTIO_PCI_QUEUE_PFN rather than the PCI address 0x80001234 as I would expect. Following this I've tried to configure the address in the virtio descriptors with both the CPU address and PCI address and neither seems to work in my tests here. Looking through the virtio code I can't see any references to pci_dma_read()/pci_dma_write() so I was wondering if someone can confirm whether I should be using CPU or PCI addresses when programming virtio registers and descriptors for machines such as 40p, and where I can find the address space being used for virtio device reads/writes? ATB, Mark.
