Re: Why QEMU translates one instruction to a TB？

[Philippe Mathieu-Daudé]

On 9/17/20 8:25 AM, casmac wrote:
> Hi all,
> ?0?2?0?2 ?0?2 We try to add DSP architecure to QEMU 4.2. To load the COFF 
> format
> object file, we have added loader code to load content from
> ?0?2 the object file. The rom_add_blob() function is used. We firstly
> analyze the COFF file to figure out which sections are chained
> ?0?2 together(so each chain forms a "memory blob"), and then allocate the
> memory blobs.
> ?0?2
> ?0?2 The psuedo code looks like:
> ?0?2
> ?0?2?0?2?0?2 ?0?2 ?0?2 ?0?2 for(i=0; i<BADTYPE; i++){
> ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 if(ary_sect_chain[i].exist) ?0?2 //there is a 
> chain of sections
> to allocate
> ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 {
> ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 ary_sect_chain[i].mem_region = 
> g_new(MemoryRegion, 1);
> ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 memory_region_init_ram(...);
> ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 memory_region_add_subregion(sysmem, 
> ....);
> ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 rom_add_blob(....);
> ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 ?0?2 }
> ?0?2 ?0?2 ?0?2?0?2 ?0?2 }

Why do this silly mapping when you know your DSP memory map?

> ------------------------------------------------------
> ok.lds file:
> 
> MEMORY ?0?2 /* MEMORY directive */
> {
> ?0?2 ?0?2 ROM:?0?2?0?2?0?2?0?2?0?2?0?2?0?2?0?2?0?2 ?0?2 origin = 000000h?0?2 
> ?0?2 length = 001000h?0?2?0?2 ?0?2 /* 4K
> 32-bit words on-chip ROM (C31/VC33) */

Per the TI spru031f datasheet, this is external (there is no
on-chip ROM).

I have my doubts there is actually a ROM mapped here...
Is this linkscript used to *test* a BIOS written in SRAM by
some JTAG?

> ?0?2 ?0?2 /* 256K 32-bit word off-chip SRAM (D.Module.VC33-150-S2) */
> ?0?2 ?0?2 BIOS:?0?2?0?2?0?2?0?2 ?0?2 origin = 001000h?0?2?0?2?0?2 ?0?2 length 
> = 000300h
> ?0?2 ?0?2 CONF_UTL: ?0?2 origin = 001300h?0?2?0?2?0?2 ?0?2 length = 000800h
> ?0?2 ?0?2 FREE:?0?2?0?2?0?2?0?2 ?0?2 origin = 001B00h?0?2?0?2?0?2 ?0?2 length 
> = 03F500h?0?2 /* 259328 32-bit
> words */
> ?0?2 ?0?2 RAM_0_1:?0?2?0?2 ?0?2 origin = 809800h?0?2 ?0?2 length = 
> 000800h?0?2?0?2 ?0?2 /* 2 x 1K
> 32-bit word on-chip SRAM (C31/VC33) */
> ?0?2 ?0?2 RAM_2_3:?0?2?0?2 ?0?2 origin = 800000h?0?2 ?0?2 length = 
> 008000h?0?2?0?2 ?0?2 /* 2 x 16K
> 32-bit word on-chip SRAM (VC33 only) */
> }

You probably want to use:

  memory_region_init_ram(&s->extsram, OBJECT(dev), "eSRAM",
                         256 * KiB, &error_fatal);
  memory_region_add_subregion(get_system_memory(),
                              0x000000, &s->extsram);

  memory_region_init_ram(&s->ocsram, OBJECT(dev), "iSRAM",
                         2 * KiB, &error_fatal);
  memory_region_add_subregion(get_system_memory(),
                              0x809800, &s->ocsram);

Then different areas of the object file will be loaded into
the either the iSRAM or the eSRAM.