On Apr 6, 2008, at 6:48 PM, Paul Mackerras wrote:
Kumar Gala writes:
Wanted to get any feedback on this initial port of the fixmap
support over
from x86. There are a few TODOs:
I have no objection in principle, but your patch below imports a few
things that aren't (and won't be) needed on powerpc AFAICS -- for
example, we don't need FIX_VDSO, since our VDSO is mapped into user
space at the 1MB point (by default).
Agreed.
You have FIX_PCIE_MCFG in there too (keyed off CONFIG_PCI_MMCONFIG
which we don't have and don't want to have). If you need to map in
PCIe config space, what's wrong with just using ioremap? Why do you
need to have a fixed virtual address for it?
Ben has commented on this. I know on the 83xx systems we have two
PCIe PHBs that would require ioremapping 512M of virtual address space
which we don't have if the system has any large amount of memory.
More generally, I think we need to take an overall look at what things
we are using fixed virtual addresses for, and why they need to be
fixed. If there are indeed several such things then we can introduce
the fixmap stuff.
The list as I see it:
* kmap
* pci-e config for 4xx/83xx
* kexec/kdump (ben commented on this when Dale posted his patches for
ppc32 support)
future:
* possible usage by HV
since we already have three users and a possible fourth it seems like
a useful change.
- k
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