Re: [PATCH for-7.2 v2 09/20] hw/ppc: set machine->fdt in pnv_reset()

[Daniel Henrique Barboza]

On 8/8/22 04:13, Cédric Le Goater wrote:
> On 8/8/22 08:47, Cédric Le Goater wrote:
> > On 8/5/22 11:39, Daniel Henrique Barboza wrote:
> > > This will enable support for 'dumpdtb' and 'info fdt' HMP commands for
> > > all powernv machines.
> >
> > I might have missed some emails but dumpdtb is already suppported :
> > commit 8d4092614161 ("ppc/pnv: activate the "dumpdtb" option on the
> > powernv machine")
>
> ok. found the patchset "QMP/HMP: add 'dumpdtb' and 'info fdt' commands"
>
> 'info fdt' would have been of great help when we were developing the
> PowerNV machine. Initially, I was even using pmemsave to extract the
> FDT blob ... So this is a great idea ! (which needs a g_free() )
>
> Do we have something similar to dump ACPI tables, btw ?

In QEMU? No idea. I didn't find users of libfdt in x86 files so I didn't
bothered checking.

I am aware of something you can do in userland to dump the ACPI tables. I
did it once for research when I was working in the NUMA FORM2 extension
for pseries. This is the procedure do dump the ACPI SLIT table:


danielhb@ubuntu-vm:~$ sudo acpidump > acpidata.dat
[sudo] password for danielhb:
danielhb@ubuntu-vm:~$
danielhb@ubuntu-vm:~$ sudo acpixtract -sSLIT acpidata.dat

Intel ACPI Component Architecture
ACPI Binary Table Extraction Utility version 20200925
Copyright (c) 2000 - 2020 Intel Corporation

  SLIT -      60 bytes written (0x0000003C) - slit.dat
danielhb@ubuntu-vm:~$
danielhb@ubuntu-vm:~$ iasl -d slit.dat

Intel ACPI Component Architecture
ASL+ Optimizing Compiler/Disassembler version 20200925
Copyright (c) 2000 - 2020 Intel Corporation

File appears to be binary: found 24 non-ASCII characters, disassembling
Binary file appears to be a valid ACPI table, disassembling
Input file slit.dat, Length 0x3C (60) bytes
ACPI: SLIT 0x0000000000000000 00003C (v01 BOCHS  BXPCSLIT 00000001 BXPC 
00000001)
Acpi Data Table [SLIT] decoded
Formatted output:  slit.dsl - 1489 bytes
danielhb@ubuntu-vm:~$
danielhb@ubuntu-vm:~$ cat slit.dsl
/*
 * Intel ACPI Component Architecture
 * AML/ASL+ Disassembler version 20200925 (64-bit version)
 * Copyright (c) 2000 - 2020 Intel Corporation
 *
 * Disassembly of slit.dat, Wed Jun  2 19:00:54 2021
 *
 * ACPI Data Table [SLIT]
 *
 * Format: [HexOffset DecimalOffset ByteLength]  FieldName : FieldValue
 */

[000h 0000   4]                    Signature : "SLIT"    [System Locality 
Information Table]
[004h 0004   4]                 Table Length : 0000003C
[008h 0008   1]                     Revision : 01
[009h 0009   1]                     Checksum : A0
[00Ah 0010   6]                       Oem ID : "BOCHS "
[010h 0016   8]                 Oem Table ID : "BXPCSLIT"
[018h 0024   4]                 Oem Revision : 00000001
[01Ch 0028   4]              Asl Compiler ID : "BXPC"
[020h 0032   4]        Asl Compiler Revision : 00000001

[024h 0036   8]                   Localities : 0000000000000004
[02Ch 0044   4]                 Locality   0 : 0A 16 16 16
[030h 0048   4]                 Locality   1 : 2C 0A 2C 2C
[034h 0052   4]                 Locality   2 : 42 42 0A 42
[038h 0056   4]                 Locality   3 : 58 58 58 0A

Raw Table Data: Length 60 (0x3C)

    0000: 53 4C 49 54 3C 00 00 00 01 A0 42 4F 43 48 53 20  // SLIT<.....BOCHS
    0010: 42 58 50 43 53 4C 49 54 01 00 00 00 42 58 50 43  // BXPCSLIT....BXPC
    0020: 01 00 00 00 04 00 00 00 00 00 00 00 0A 16 16 16  // ................
    0030: 2C 0A 2C 2C 42 42 0A 42 58 58 58 0A              // ,.,,BB.BXXX.
danielhb@ubuntu-vm:~$


So basically a combination of acpidump and acpixtract commands in the guest.


Daniel


> Thanks,
>
> C.
>
>
> > > Cc: Cédric Le Goater <clg@kaod.org>
> > > Cc: Frederic Barrat <fbarrat@linux.ibm.com>
> > > Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> > > ---
> > >   hw/ppc/pnv.c | 6 +++++-
> > >   1 file changed, 5 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/hw/ppc/pnv.c b/hw/ppc/pnv.c
> > > index d3f77c8367..f5162f8b7b 100644
> > > --- a/hw/ppc/pnv.c
> > > +++ b/hw/ppc/pnv.c
> > > @@ -608,7 +608,11 @@ static void pnv_reset(MachineState *machine)
> > >       qemu_fdt_dumpdtb(fdt, fdt_totalsize(fdt));
> > >       cpu_physical_memory_write(PNV_FDT_ADDR, fdt, fdt_totalsize(fdt));
> > > -    g_free(fdt);
> > > +    /*
> > > +     * Update the machine->fdt pointer to enable support for
> > > +     * 'dumpdtb' and 'info fdt' commands.
> > > +     */
> > > +    machine->fdt = fdt;
> > >   }
> > >   static ISABus *pnv_chip_power8_isa_create(PnvChip *chip, Error **errp)