From: Jane Chu <jane.chu@xxxxxxxxxx>
Date: Mon, 5 Jun 2017 16:48:31 -0600
> Linux SPARC64 limits NR_CPUS to 4064 because init_cpu_send_mondo_info()
> only allocates a single page for NR_CPUS mondo entries. Thus we cannot
> use all 4096 CPUs on some SPARC platforms.
>
> To fix, allocate (2^order) pages where order is set according to the size
> of cpu_list for possible cpus. Since cpu_list_pa and cpu_mondo_block_pa
> are not used in asm code, there are no imm13 offsets from the base PA
> that will break because they can only reach one page.
>
> Orabug: 25505750
>
> Signed-off-by: Jane Chu <jane.chu@xxxxxxxxxx>
>
> Reviewed-by: Bob Picco <bob.picco@xxxxxxxxxx>
> Reviewed-by: Atish Patra <atish.patra@xxxxxxxxxx>
> ---
> arch/sparc/Kconfig | 4 ++--
> arch/sparc/kernel/irq_64.c | 16 ++++++++++++----
> 2 files changed, 14 insertions(+), 6 deletions(-)
>
> diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
> index 58243b0..4399be7 100644
> --- a/arch/sparc/Kconfig
> +++ b/arch/sparc/Kconfig
> @@ -192,9 +192,9 @@ config NR_CPUS
> int "Maximum number of CPUs"
> depends on SMP
> range 2 32 if SPARC32
> - range 2 1024 if SPARC64
> + range 2 4096 if SPARC64
> default 32 if SPARC32
> - default 64 if SPARC64
> + default 4096 if SPARC64
>
> source kernel/Kconfig.hz
>
> diff --git a/arch/sparc/kernel/irq_64.c b/arch/sparc/kernel/irq_64.c
> index 4d0248a..cc8f6c3 100644
> --- a/arch/sparc/kernel/irq_64.c
> +++ b/arch/sparc/kernel/irq_64.c
> @@ -1034,17 +1034,25 @@ static void __init init_cpu_send_mondo_info(struct trap_per_cpu *tb)
> {
> #ifdef CONFIG_SMP
> unsigned long page;
> + void *mondo;
>
> - BUILD_BUG_ON((NR_CPUS * sizeof(u16)) > (PAGE_SIZE - 64));
> + BUILD_BUG_ON((NR_CPUS * sizeof(u16)) > PAGE_SIZE);
> +
> + /* Make sure mondo block is 64byte aligned */
> + mondo = kzalloc(64, GFP_KERNEL);
> + if (!mondo) {
> + prom_printf("SUN4V: Error, cannot allocate mondo block.\n");
> + prom_halt();
> + }
> + tb->cpu_mondo_block_pa = __pa(mondo);
Hmmm, you said that this has to be 64 byte aligned right? We might have
to do something in order to insure that, as kmalloc() only guarantees
ARCH_KMALLOC_MINALIGN which I think is 8 on sparc.
I suppose this would work:
mondo = kzalloc(64 + 63, GFP_KERNEL);
and then 64-byte align that pointer.
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