[PATCH 1/2] ARM: vexpress: refine MCPM smp operations override criteria
Liviu Dudau
liviu.dudau at arm.com
Fri Sep 23 08:00:04 PDT 2016
On Fri, Sep 23, 2016 at 02:09:06PM +0100, Lorenzo Pieralisi wrote:
> Current vexpress smp init code detects whether to override the
> default smp ops with MCPM smp ops by matching the "cci-400"
> compatible string, in that MCPM requires control over CCI ports
> to manage low-power states entry/exit.
>
> The "cci-400" compatible string check is a necessary but not
> sufficient condition for MCPM to work, because the cci-400
> can be made visible to the kernel, but firmware can nonetheless
> disable non-secure CCI ports control, while still allowing PMU
> access; if booted in non-secure world, the kernel would still
> blindly override smp operations with MCPM operations, resulting
> in kernel faults when the CCI ports programming interface is
> accessed from non-secure world.
>
> This means that the "cci-400" compatible string check would
> result in a false positive in systems that eg boot in HYP mode,
> where CCI ports non-secure access is explicitly not allowed,
> and it is reported in the respective device tree nodes with
> CCI ports marked as disabled.
I remember seeing a patch from Marc this week exactly on this
subject, but I can't find it again today. However, I remember that
his patch was explicitly testing for the HYP presence.
>
> Refactor the smp operations initialization to make sure that
> the kernel is actually allowed to take control over CCI ports
> (by enabling MCPM smp operations) before overriding default
> vexpress smp operations.
>
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
> Cc: Liviu Dudau <liviu.dudau at arm.com>
> Cc: Sudeep Holla <sudeep.holla at arm.com>
> Cc: Nicolas Pitre <nicolas.pitre at linaro.org>
> Cc: Marc Zyngier <marc.zyngier at arm.com>
> ---
> arch/arm/mach-vexpress/platsmp.c | 31 ++++++++++++++++++++++++-------
> 1 file changed, 24 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm/mach-vexpress/platsmp.c b/arch/arm/mach-vexpress/platsmp.c
> index 8b8d072..6cfd782 100644
> --- a/arch/arm/mach-vexpress/platsmp.c
> +++ b/arch/arm/mach-vexpress/platsmp.c
> @@ -26,17 +26,34 @@
> bool __init vexpress_smp_init_ops(void)
> {
> #ifdef CONFIG_MCPM
> + int cpu;
> + struct device_node *cpu_node, *cci_node;
> +
> /*
> - * The best way to detect a multi-cluster configuration at the moment
> - * is to look for the presence of a CCI in the system.
> + * The best way to detect a multi-cluster configuration
> + * is to detect if the kernel can take over CCI ports
> + * control. Loop over possible CPUs and check if CCI
> + * port control is available.
> * Override the default vexpress_smp_ops if so.
> */
> - struct device_node *node;
> - node = of_find_compatible_node(NULL, NULL, "arm,cci-400");
> - if (node && of_device_is_available(node)) {
> - mcpm_smp_set_ops();
> - return true;
> + for_each_possible_cpu(cpu) {
> + bool available;
> +
> + cpu_node = of_get_cpu_node(cpu, NULL);
> + if (WARN(!cpu_node, "Missing cpu device node!"))
> + return false;
> +
> + cci_node = of_parse_phandle(cpu_node, "cci-control-port", 0);
> + available = cci_node && of_device_is_available(cci_node);
of_device_is_available() only checks the DT node for status = "enabled";
Does the HYP modify the DT to disable the cci-control-port? If not, then I guess
this patch is not enough?
Best regards,
Liviu
> + of_node_put(cci_node);
> + of_node_put(cpu_node);
> +
> + if (!available)
> + return false;
> }
> +
> + mcpm_smp_set_ops();
> + return true;
> #endif
> return false;
> }
> --
> 2.10.0
>
--
====================
| I would like to |
| fix the world, |
| but they're not |
| giving me the |
\ source code! /
---------------
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