Hi Becky,
Becky Bruce wrote:
Folks,
We're going to be seeing more platforms with larger physical addresses (PA) than virtual addresses (VA) supported in u-boot, and this kind of ruins the current assumption inherent in much of u-boot that VA == PA. On ppc, we've begin implementing the ability to actually translate VAs to PAs and vice-versa. But this brings up the question of, when I type an address on the command line, what exactly am I specifying? Is that a virtual address, or a physical address?
Wolfgang and I talked about this on IRC a bit earlier, and what we're proposing is this:
[snip good discussion]
- Initially, a xlat (or insert better name here) command-line command
will be added to give you a PA given a VA, and vice-versa.
How would xlat know which direction it is to translate?
Thoughts: vtop(virtual) returns physical ptov(physical) returns virtual or (see below thought on 0v / 0p) xlat(0p1234) returns virtual xlat(0v1234) returns physical xlat(0x1234) returns physical (per convention from snipped discussion)
I'm not wild about xlat doing dual duty (I'm not wild about vtop/ptov either but like it a little better). Shock but no awe. :-/
Question: Do we need a translation function?
- Going forward, commands will be extended to take either a VA or PA
at the command line, with the syntax for this TBD and per argument (i.e. if a command takes multiple addresses, each one can be either a va or pa, and they can be intermingled). The default will remain VA if no modifier is specified.
Thought: 0v6789ABCD is a virtual address (the value is interpreted as hex) 0p6789ABCD is a physical address
Of course "v" and "p" should be accepted in either case.
Kinda ugly, but fits into the 0x style conventions.
I haven't looked at the number parsing code to see how hard it would be to squeeze this into it.
Note that unless your platform actually has enabled configs with VA != PA (which is just MPC8641D at the moment, as far as I know), things will look exactly the same as they always have.
Comments? I'm looking for some consensus here before I spend my weekend writing a whole bunch of code.
Stuff face, write code. Does it get any better than that? ;-)
Cheers, Becky
Have a great Thanksgiving, gvb