Re: Read SPI BAR offset 0x10 throwing processor exception

Michael Brown

On 28/01/2022 12:47, Rao G wrote:
Attempting to Read SPIBAR 0x10 from BUS 0 Dev 1F Func 5

ScSpiBar0 = MmioRead32 (SpiInstance->PchSpiBase + PCI_BASE_ADDRESSREG_OFFSET) & 0xFFFFF000;
The above code is throwing exception
PchSpiBase at 0xC00FD000
!!!! X64 Exception Type - 0E(#PF - Page-Fault)  CPU Apic ID - 00000000 !!!!
ExceptionData - 0000000000000000  I:0 R:0 U:0 W:0 P:0 PK:0 SS:0 SGX:0
RIP  - 00000000771903D0, CS  - 0000000000000038, RFLAGS - 0000000000010046
From the shell the value at offset 0x10 is 0xFE010000
Any clues on why the processor is throwing exception while accessing the value PchSpiBase+0x10 ?
PCI_BASE_ADDRESSREG_OFFSET is an offset within PCI configuration space. It looks as though you are trying to use an MMIO access to read from PCI configuration space, which is not a valid thing to do.

I suspect you may want to use EFI_PCI_IO_PROTOCOL.Pci.Read() instead.



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