[Qemu-devel] [PATCH][MIPS] Fix for the scd instruction

[Aurelien Jarno]

Hi,

The scd instruction is not correctly implemented. In op_mem.c a 1 or a
0 is returned in T0 depending on the success or not of the RMW sequence.
However in translate.c, the result is never copied back to the register.

The trivial patch below fixes that.

Please also find below a boot of a 64-bit kernel on the MIPS target. I
guess the next step is to implement 64-bit TLB.

Bye,
Aurelien


(qemu) Linux version 2.6.21.1 (address@hidden) (gcc version 4.1.1 ()) #1 Sun 
May 6 21:43:32 CEST 2007

LINUX started...
CPU revision is: 00000400
FPU revision is: 00730400
registering PCI controller with io_map_base unset
Determined physical RAM map:
 memory: 0000000000001000 @ 0000000000000000 (reserved)
 memory: 00000000000ef000 @ 0000000000001000 (ROM data)
 memory: 0000000000464000 @ 00000000000f0000 (reserved)
 memory: 0000000007aab000 @ 0000000000554000 (usable)
Wasting 76384 bytes for tracking 1364 unused pages
Initrd not found or empty - disabling initrd
Built 1 zonelists.  Total pages: 32320
Kernel command line: root=/dev/hda1 console=ttyS0
Primary instruction cache 4kB, physically tagged, direct mapped, linesize 16 
bytes.
Primary data cache 16kB, direct mapped, linesize 16 bytes.
Unified secondary cache 128kB direct mapped, linesize 16 bytes.
Synthesized TLB refill handler (39 instructions).
Synthesized TLB load handler fastpath (51 instructions).
Synthesized TLB store handler fastpath (51 instructions).
Synthesized TLB modify handler fastpath (50 instructions).
PID hash table entries: 512 (order: 9, 4096 bytes)
CPU frequency 200.05 MHz
Using 100.023 MHz high precision timer.



Index: target-mips/translate.c
===================================================================
RCS file: /sources/qemu/qemu/target-mips/translate.c,v
retrieving revision 1.70
diff -u -d -p -r1.70 translate.c
--- target-mips/translate.c     9 May 2007 09:33:33 -0000       1.70
+++ target-mips/translate.c     9 May 2007 20:00:54 -0000
@@ -745,6 +745,7 @@ static void gen_ldst (DisasContext *ctx,
         save_cpu_state(ctx, 1);
         GEN_LOAD_REG_TN(T1, rt);
         op_ldst(scd);
+        GEN_STORE_TN_REG(rt, T0);
         opn = "scd";
         break;
     case OPC_LDL:

-- 
  .''`.  Aurelien Jarno             | GPG: 1024D/F1BCDB73
 : :' :  Debian developer           | Electrical Engineer
 `. `'   address@hidden         | address@hidden
   `-    people.debian.org/~aurel32 | www.aurel32.net