On 24/05/13 10:54, Alex Markuze wrote:
I’ve noticed that the iPXE code has macros and comments regarding the
support of 64 bit BAR addresses.
Has this code been ever validated? Does it work or does it still need
patching?
The code is working as far as I know.
The special handling for 64-bit BARs is twofold: firstly we need to
detect BARs that are 64-bit capable and treat them as such (i.e. treat
the next BAR as the high dword rather than being a separate BAR);
secondly we need to fail to map 64-bit capable BARs if there's no way
for the CPU to access them (i.e. if the BIOS has assigned an address
above 4GB and we are running a 32-bit binary).
Most BIOSes should assign addresses below 4GB even for 64-bit capable
BARs, to allow for access from within a 32-bit OS.
Under UEFI, the problem goes away since we (usually) run as a 64-bit binary.
Michael
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