Re: [Qemu-devel] [PATCH RFC] spapr: by-pass SLOF when -kernel is provided

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Jul 05, 2016 at 04:42:37PM +0200, Laurent Vivier wrote:
> As device-tree is now fully built by QEMU, we don't need SLOF
> anymore if the kernel is provided on the command line.
> 
> In this case, don't load SLOF and boot directly into the
> kernel.
> 
> This saves at least 5 seconds on the boot sequence.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>

I'm not comfortable applying this.  We actually used to do this ages
ago, but changed to always running through SLOF, and there were
reasons for doing so.

I don't remember exactly what they were, but I think it boiled down to
slight differences in state between booting from SLOF and booting
without SLOF leading to confusing errors from the guest kernel.

> ---
>  hw/ppc/spapr.c | 37 ++++++++++++++++++++-----------------
>  1 file changed, 20 insertions(+), 17 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 7f33a1b..bbdb21d 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1219,8 +1219,11 @@ static void ppc_spapr_reset(void)
>      first_ppc_cpu->env.gpr[3] = spapr->fdt_addr;
>      first_ppc_cpu->env.gpr[5] = 0;
>      first_cpu->halted = 0;
> -    first_ppc_cpu->env.nip = SPAPR_ENTRY_POINT;
> -
> +    if (machine->kernel_filename) {
> +        first_ppc_cpu->env.nip = KERNEL_LOAD_ADDR;
> +    } else {
> +        first_ppc_cpu->env.nip = SPAPR_ENTRY_POINT;
> +    }
>  }
>  
>  static void spapr_create_nvram(sPAPRMachineState *spapr)
> @@ -2023,23 +2026,23 @@ static void ppc_spapr_init(MachineState *machine)
>              initrd_base = 0;
>              initrd_size = 0;
>          }
> +    } else {
> +        if (bios_name == NULL) {
> +            bios_name = FW_FILE_NAME;
> +        }
> +        filename = qemu_find_file(QEMU_FILE_TYPE_BIOS, bios_name);
> +        if (!filename) {
> +            error_report("Could not find LPAR firmware '%s'", bios_name);
> +            exit(1);
> +        }
> +        fw_size = load_image_targphys(filename, 0, FW_MAX_SIZE);
> +        if (fw_size <= 0) {
> +            error_report("Could not load LPAR firmware '%s'", filename);
> +            exit(1);
> +        }
> +        g_free(filename);
>      }
>  
> -    if (bios_name == NULL) {
> -        bios_name = FW_FILE_NAME;
> -    }
> -    filename = qemu_find_file(QEMU_FILE_TYPE_BIOS, bios_name);
> -    if (!filename) {
> -        error_report("Could not find LPAR firmware '%s'", bios_name);
> -        exit(1);
> -    }
> -    fw_size = load_image_targphys(filename, 0, FW_MAX_SIZE);
> -    if (fw_size <= 0) {
> -        error_report("Could not load LPAR firmware '%s'", filename);
> -        exit(1);
> -    }
> -    g_free(filename);
> -
>      /* FIXME: Should register things through the MachineState's qdev
>       * interface, this is a legacy from the sPAPREnvironment structure
>       * which predated MachineState but had a similar function */

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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