Re: [Qemu-devel] [PATCH] sparc64 support TSB related MMU registers

[Blue Swirl <blauwirbel@gmail.com>]

On 4/24/09, Igor Kovalenko <igor.v.kovalenko@gmail.com> wrote:
> Hi!
>
>  This change allows reading ultrasparc I/D MMU TSB tag target register
>  and TSB pointer register (8k and 64k).
>  Linux kernel uses TSB for memory management, and with this change it
>  now can use early allocation routines.
>
>  I'm testing with linux-2.6.29.1 minimalistic sparc64 uniprocessor
>  build, now kernel is able to start build device tree.
>  Without the change kernel was not able to handle D-MMU miss while
>  creating first device tree node.
>  Currently it stops shortly after building device tree, trying to find
>  out path to console.

Nice, though I didn't notice any visible improvement in my tests.

About the patch, there are a few problems:
- it breaks Sparc32
- commented out code is ugly
- if and else should be on the same line as '{' or '}'
- long lines should be wrapped
- in the line:
+    return (((tag_access_register & 0x1fff)<<48)|(tag_access_register >> 22));
 there should be white space between ) and << and 48.

>  (PS with openbios instance-to-path method fails in client interface
>  call, in the same way
>  it fails without loading kernel when I try invoking get-instance-path
>  on stdin handle from command prompt.
>  there fmove invokes memmove() with size argument looking like some
>  pointer which leads to unhandled D-MMU fault)

Similar very obscure problem was fixed with PPC (r481), the bug was
with the PCI nodes.