Re: [Qemu-devel] [PATCH qemu RFC 2/4] spapr: Allow bios-less configuration

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

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On Sat, Jul 20, 2019 at 11:28:48AM +1000, Alexey Kardashevskiy wrote:
> The pseries kernel can do either usual prom-init boot or kexec style boot.
> We always did the prom-init which relies on the completeness of
> the device tree (for example, PCI BARs have to be assigned beforehand) and
> the client interface; the system firmware (SLOF) implements this.
> 
> However we can use the kexec style boot as well. To do that, we can skip
> loading SLOF and jump straight to the kernel. GPR5==0 (the client
> interface entry point, SLOF passes a valid pointer there) tells Linux to
> do the kexec boot rather than prom_init so it can proceed to the initramfs.
> With few PCI fixes in the guest kernel, it can boot from PCI (via
> petitboot, for example).
> 
> This adds a "bios" machine option which controls whether QEMU loads SLOF
> or jumps directly to the kernel. When bios==off, this does not copy SLOF
> and RTAS into the guest RAM and sets RTAS properties to 0 to bypass
> the kexec user space tool which checks for their presence (not for
> the values though).

BIOS is sometimes used to refer to any machine's firmware, but it's
also used to refer specifically to PC style BIOS.  I think it would be
clearer to be explicit here and call the options "slof" rather than
"bios".

> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
>  include/hw/ppc/spapr.h |  1 +
>  hw/ppc/spapr.c         | 58 ++++++++++++++++++++++++++++++++----------
>  2 files changed, 45 insertions(+), 14 deletions(-)
> 
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index ff82bb8554e1..7f5d7a70d27e 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -160,6 +160,7 @@ struct SpaprMachineState {
>      long kernel_size;
>      bool kernel_le;
>      uint64_t kernel_addr;
> +    bool bios_enabled;
>      uint32_t initrd_base;
>      long initrd_size;
>      uint64_t rtc_offset; /* Now used only during incoming migration */
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 6d13d65d8996..81ad6a6f28de 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1116,6 +1116,10 @@ static void spapr_dt_rtas(SpaprMachineState *spapr, void *fdt)
>      _FDT(fdt_setprop(fdt, rtas, "ibm,lrdr-capacity",
>                       lrdr_capacity, sizeof(lrdr_capacity)));
>  
> +    /* These are to make kexec-lite happy */
> +    _FDT(fdt_setprop_cell(fdt, rtas, "linux,rtas-base", 0));
> +    _FDT(fdt_setprop_cell(fdt, rtas, "rtas-size", 0));

What exactly is kexec-lite and what does it need here?

>      spapr_dt_rtas_tokens(fdt, rtas);
>  }
>  
> @@ -1814,7 +1818,11 @@ static void spapr_machine_reset(MachineState *machine)
>      spapr->fdt_blob = fdt;
>  
>      /* Set up the entry state */
> -    spapr_cpu_set_entry_state(first_ppc_cpu, SPAPR_ENTRY_POINT, fdt_addr);
> +    if (!spapr->bios_enabled) {
> +        spapr_cpu_set_entry_state(first_ppc_cpu, spapr->kernel_addr, fdt_addr);
> +    } else {
> +        spapr_cpu_set_entry_state(first_ppc_cpu, SPAPR_ENTRY_POINT, fdt_addr);
> +    }
>      first_ppc_cpu->env.gpr[5] = 0;
>  
>      spapr->cas_reboot = false;
> @@ -3031,20 +3039,22 @@ static void spapr_machine_init(MachineState *machine)
>          }
>      }
>  
> -    if (bios_name == NULL) {
> -        bios_name = FW_FILE_NAME;
> +    if (spapr->bios_enabled) {
> +        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);
>      }
> -    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
> @@ -3266,6 +3276,20 @@ static void spapr_set_kernel_addr(Object *obj, Visitor *v, const char *name,
>      visit_type_uint64(v, name, (uint64_t *)opaque, errp);
>  }
>  
> +static bool spapr_get_bios_enabled(Object *obj, Error **errp)
> +{
> +    SpaprMachineState *spapr = SPAPR_MACHINE(obj);
> +
> +    return spapr->bios_enabled;
> +}
> +
> +static void spapr_set_bios_enabled(Object *obj, bool value, Error **errp)
> +{
> +    SpaprMachineState *spapr = SPAPR_MACHINE(obj);
> +
> +    spapr->bios_enabled = value;
> +}
> +
>  static char *spapr_get_ic_mode(Object *obj, Error **errp)
>  {
>      SpaprMachineState *spapr = SPAPR_MACHINE(obj);
> @@ -3379,6 +3403,12 @@ static void spapr_instance_init(Object *obj)
>                                      " for -kernel is the default",
>                                      NULL);
>      spapr->kernel_addr = KERNEL_LOAD_ADDR;
> +    object_property_add_bool(obj, "bios", spapr_get_bios_enabled,
> +                            spapr_set_bios_enabled, NULL);
> +    object_property_set_description(obj, "bios", "Conrols whether to load bios",
> +                                    NULL);
> +    spapr->bios_enabled = true;
> +
>      /* The machine class defines the default interrupt controller mode */
>      spapr->irq = smc->irq;
>      object_property_add_str(obj, "ic-mode", spapr_get_ic_mode,

-- 
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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