On Wed, Jul 13, 2016 at 03:05:31PM +0530, Aneesh Kumar K.V wrote:
> This patch adds the kernel command line disable_radix which disable
> the radix MMU mode even if firmware indicates radix support via
> ibm,pa-features device tree node.
>
> This helps in testing different MMU mode easily.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com>
> ---
> Documentation/kernel-parameters.txt | 3 +++
> arch/powerpc/kernel/prom.c | 13 +++++++++++++
> 2 files changed, 16 insertions(+)
>
> diff --git a/Documentation/kernel-parameters.txt
> b/Documentation/kernel-parameters.txt
> index 738bae4a5958..bba7ef30d74e 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -929,6 +929,9 @@ bytes respectively. Such letter suffixes can also be
> entirely omitted.
> disable= [IPV6]
> See Documentation/networking/ipv6.txt.
>
> + disable_radix [PPC]
> + Disable RADIX MMU mode on POWER9
> +
> disable_cpu_apicid= [X86,APIC,SMP]
> Format: <int>
> The number of initial APIC ID for the
> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
> index 946e34ffeae9..022540b9366d 100644
> --- a/arch/powerpc/kernel/prom.c
> +++ b/arch/powerpc/kernel/prom.c
> @@ -645,6 +645,14 @@ static void __init early_reserve_mem(void)
> #endif
> }
>
> +static bool disable_radix;
__read_mostly?
> +static int __init parse_disable_radix(char *p)
> +{
> + disable_radix = true;
> + return 0;
> +}
> +early_param("disable_radix", parse_disable_radix);
> +
> void __init early_init_devtree(void *params)
> {
> phys_addr_t limit;
> @@ -739,6 +747,11 @@ void __init early_init_devtree(void *params)
> /* Scan and build the list of machine check recoverable ranges */
> of_scan_flat_dt(early_init_dt_scan_recoverable_ranges, NULL);
> #endif
> + /*
> + * now fixup radix MMU mode based on kernel command line
> + */
> + if (disable_radix)
> + cur_cpu_spec->mmu_features &= ~MMU_FTR_RADIX;
Shouldn't this happen before prom_init() and exchanging capabilities?
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