Re: [linuxsh-dev] BUG fix for VMALLOC-ed page

[Greg B. <gb...@po...>]

NIIBE Yutaka wrote:
> 
>  > > * freeze/snapshot feature ---> dump .data & .bss, reload, kick the driver...
>  >
>  >   Sorry, I don't understand what this means.
> 
> You know, some nortebook computer has the feature of "Hibernation",
> let the RAM image go into the disk.  This entry is for that.
  
  Is that .data and .bss (and stack) of all processes and the kernel?
That would be a very useful feature, especially if you could power down
all modules and put the processor into Standby mode.

>  > > * PCMCIA(SH-4) TLB wiring, conservative TLB initialization
>  >
>  >   And this?
> 
> To use PCMCIA feature on SH-4, we need to use MMU, because some bits
> are assigned to the bit on TLB to access PCMCIA (area 5 and 6).

  Yes, the C (cached) and WT (write-through) bits.

>  We
> think that such initialization of the specific hardware (the bus) is
> the job of initialization routine (BIOS).

  Within reason.  For example, you don't expect the BIOS to handle
interrupts, so that part of the initialisation is done by the kernel
itself.  So the BIOS doesn't do everything necessary to initialise.

>  Currently, the kernel
> assumes BIOS doesn't use MMU and flush out all the TLB on boot, which
> is not good.

  I think flushing all TLB entries on boot is a good idea, because it
puts the TLB into a known good state.  Otherwise the kernel has to somehow
figure out which TLB entries are "good" and which are possibly left over
from earlier kernel or BIOS mappings and should be thrown away.  If you're
going to go to that much effort you might as well re-construct the TLB
from scratch, it will be safer.

  Perhaps a better approach would be to just add PTEs for the PCMCIA
space to the kernel PGD, so they can be loaded into the TLB as necessary
using the usual page-fault mechanism.  Or am I missing something important?

>  >   Yes!  BTW can you explain the current status of binutils & glibc -- is
>  > libc.so supposed to link with current versions or am I doing something wrong?
> 
> For Binutils and GCC, the changes are already incorporated into
> current development repository.  Now we need to test and check again.

  Ok.

>  >   I noticed the absence of any mention of cache problems in the list -- does
>  > this mean they've all been solved?
> 
> I think that I've done the fix.  Next, we need to keep up the transition
> of the development kernel, please look at Documentation/cachetlb.txt in
> test8-pre1.

  Ok, I'll take a look at that.


Greg.
-- 
These are my opinions not PPIs.