Re: [PATCH for-7.2 v2 10/20] hw/ppc: set machine->fdt in spapr machine

[Alexey Kardashevskiy]

On 05/08/2022 19:39, Daniel Henrique Barboza wrote:
> The pSeries machine never bothered with the common machine->fdt
> attribute. We do all the FDT related work using spapr->fdt_blob.
>
> We're going to introduce HMP commands to read and save the FDT, which
> will rely on setting machine->fdt properly to work across all machine
> archs/types.


Out of curiosity - why new HMP command, is not QOM'ing this ms::fdt 
property enough?

Another thing is that on every HMP dump I'd probably rebuild the entire 
FDT for the reasons David explained. Thanks,


> Let's set machine->fdt in the two places where we manipulate the FDT:
> spapr_machine_reset() and CAS. spapr->fdt_blob is left untouched: what
> we want is a way to access the FDT from HMP, not replace
> spapr->fdt_blob.
>
> Cc: Cédric Le Goater <clg@kaod.org>
> Cc: qemu-ppc@nongnu.org
> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> ---
>   hw/ppc/spapr.c       | 6 ++++++
>   hw/ppc/spapr_hcall.c | 8 ++++++++
>   2 files changed, 14 insertions(+)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index bc9ba6e6dc..94c90f0351 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1713,6 +1713,12 @@ static void spapr_machine_reset(MachineState *machine)
>       spapr->fdt_initial_size = spapr->fdt_size;
>       spapr->fdt_blob = fdt;
>   
> +    /*
> +     * Set the common machine->fdt pointer to enable support
> +     * for 'dumpdtb' and 'info fdt' commands.
> +     */
> +    machine->fdt = fdt;
> +
>       /* Set up the entry state */
>       first_ppc_cpu->env.gpr[5] = 0;
>   
> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> index a8d4a6bcf0..0079bc6fdc 100644
> --- a/hw/ppc/spapr_hcall.c
> +++ b/hw/ppc/spapr_hcall.c
> @@ -1256,6 +1256,14 @@ target_ulong do_client_architecture_support(PowerPCCPU 
> *cpu,
>       spapr->fdt_initial_size = spapr->fdt_size;
>       spapr->fdt_blob = fdt;
>   
> +    /*
> +     * Set the machine->fdt pointer again since we just freed
> +     * it above (by freeing spapr->fdt_blob). We set this
> +     * pointer to enable support for 'dumpdtb' and 'info fdt'
> +     * HMP commands.
> +     */
> +    MACHINE(spapr)->fdt = fdt;
> +
>       return H_SUCCESS;
>   }
>   

--
Alexey