On Wed, Jul 31, 2024 at 06:52:35PM +0530, Aditya Gupta wrote:
> Currently any device tree passed with -dtb option in QEMU, was ignored
> by the PowerNV code.
>
> Read and pass the passed -dtb to the kernel, thus enabling easier
> debugging with custom DTBs.
>
> The existing behaviour when -dtb is 'not' passed, is preserved as-is.
>
> But when a '-dtb' is passed, it completely overrides any dtb nodes or
> changes QEMU might have done, such as '-append' arguments to the kernel
> (which are mentioned in /chosen/bootargs in the dtb), hence add warning
> when -dtb is being used
>
> Signed-off-by: Aditya Gupta <adit...@linux.ibm.com>
>
> ---
> This is an RFC patch, and hence might not be the final implementation,
> though this current one is a solution which works
> ---
> ---
> hw/ppc/pnv.c | 29 ++++++++++++++++++++++++++---
> 1 file changed, 26 insertions(+), 3 deletions(-)
>
> diff --git a/hw/ppc/pnv.c b/hw/ppc/pnv.c
> index 3526852685b4..12cc909b9e26 100644
> --- a/hw/ppc/pnv.c
> +++ b/hw/ppc/pnv.c
> @@ -714,6 +714,8 @@ static void pnv_reset(MachineState *machine,
> ShutdownCause reason)
> PnvMachineState *pnv = PNV_MACHINE(machine);
> IPMIBmc *bmc;
> void *fdt;
> + FILE *fdt_file;
> + uint32_t fdt_size;
>
> qemu_devices_reset(reason);
>
> @@ -736,10 +738,31 @@ static void pnv_reset(MachineState *machine,
> ShutdownCause reason)
> }
> }
>
> - fdt = pnv_dt_create(machine);
> + if (machine->dtb) {
> + warn_report("with manually passed dtb, some options like '-append'"
> + " might ignored and the dtb passed will be used as-is");
Check whether append is actually set, and report an fatal error in
that case.
>
> - /* Pack resulting tree */
> - _FDT((fdt_pack(fdt)));
> + fdt = g_malloc0(FDT_MAX_SIZE);
> +
> + /* read the file 'machine->dtb', and load it into 'fdt' buffer */
> + fdt_file = fopen(machine->dtb, "r");
> + if (fdt_file != NULL) {
> + fdt_size = fread(fdt, sizeof(char), FDT_MAX_SIZE, fdt_file);
> + if (ferror(fdt_file) != 0) {
> + error_report("Could not load dtb '%s'",
> + machine->dtb);
> + exit(1);
> + }
> +
> + /* mark end of the fdt buffer with '\0' */
> + ((char *)fdt)[fdt_size] = '\0';
> + }
Preferrable to use g_file_get_contents()
> + } else {
> + fdt = pnv_dt_create(machine);
> +
> + /* Pack resulting tree */
> + _FDT((fdt_pack(fdt)));
> + }
>
> qemu_fdt_dumpdtb(fdt, fdt_totalsize(fdt));
> cpu_physical_memory_write(PNV_FDT_ADDR, fdt, fdt_totalsize(fdt));
> --
> 2.45.2
>
>
With regards,
Daniel
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