Subject: Re: [RFC PATCH 01/26] psci: Export configured PSCI version

From: Marc Zyngier <[email-masked]>
Date: Thu, 05 Nov 2020 09:47:09 +0000

On 2020-11-04 18:36, David Brazdil wrote:
> The version of PSCI that the kernel should use to communicate with
> firmware is typically obtained from probing PSCI_VERSION. However, that
> doesn't work for PSCI v0.1 where the host gets the information from
> DT/ACPI, or if PSCI is not supported / was disabled.
> 
> KVM's PSCI proxy for the host needs to be configured with the same
> version used by the host driver. Expose the PSCI version used by the
> host.
> 
> Signed-off-by: David Brazdil <[email-masked]>
> ---
>  drivers/firmware/psci/psci.c | 6 ++++++
>  include/linux/psci.h         | 8 ++++++++
>  2 files changed, 14 insertions(+)
> 
> diff --git a/drivers/firmware/psci/psci.c 
> b/drivers/firmware/psci/psci.c
> index 00af99b6f97c..ff523bdbfe3f 100644
> --- a/drivers/firmware/psci/psci.c
> +++ b/drivers/firmware/psci/psci.c
> @@ -49,6 +49,8 @@ static int resident_cpu = -1;
>  struct psci_operations psci_ops;
>  static enum arm_smccc_conduit psci_conduit = SMCCC_CONDUIT_NONE;
> 
> +int psci_driver_version = PSCI_VERSION(0, 0);
> +
>  bool psci_tos_resident_on(int cpu)
>  {
>  	return cpu == resident_cpu;
> @@ -461,6 +463,8 @@ static int __init psci_probe(void)
>  		return -EINVAL;
>  	}
> 
> +	psci_driver_version = ver;
> +
>  	psci_0_2_set_functions();
> 
>  	psci_init_migrate();
> @@ -514,6 +518,8 @@ static int __init psci_0_1_init(struct device_node 
> *np)
> 
>  	pr_info("Using PSCI v0.1 Function IDs from DT\n");
> 
> +	psci_driver_version = PSCI_VERSION(0, 1);
> +
>  	if (!of_property_read_u32(np, "cpu_suspend", &id)) {
>  		psci_function_id[PSCI_FN_CPU_SUSPEND] = id;
>  		psci_ops.cpu_suspend = psci_cpu_suspend;
> diff --git a/include/linux/psci.h b/include/linux/psci.h
> index 2a1bfb890e58..cb35b90d1746 100644
> --- a/include/linux/psci.h
> +++ b/include/linux/psci.h
> @@ -21,6 +21,14 @@ bool psci_power_state_is_valid(u32 state);
>  int psci_set_osi_mode(bool enable);
>  bool psci_has_osi_support(void);
> 
> +/**
> + * The version of the PSCI specification followed by the driver.
> + * This is equivalent to calling PSCI_VERSION except:
> + *   (a) it also works for PSCI v0.1, which does not support 
> PSCI_VERSION, and
> + *   (b) it is set to v0.0 if the PSCI driver was not initialized.
> + */
> +extern int psci_driver_version;
> +
>  struct psci_operations {
>  	u32 (*get_version)(void);
>  	int (*cpu_suspend)(u32 state, unsigned long entry_point);

How about providing a get_version callback for pre-0.2 implementations
instead? This would avoid exposing more symbols (psci_ops is already
global).

Thanks,

         M.

diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
index 00af99b6f97c..b84454e12d92 100644
--- a/drivers/firmware/psci/psci.c
+++ b/drivers/firmware/psci/psci.c
@@ -500,6 +500,11 @@ static int __init psci_0_2_init(struct device_node 
*np)
  	return psci_probe();
  }

+static u32 psci_0_1_get_version(void)
+{
+	return PSCI_VERSION(0, 1);
+}
+
  /*
   * PSCI < v0.2 get PSCI Function IDs via DT.
   */
@@ -514,6 +519,8 @@ static int __init psci_0_1_init(struct device_node 
*np)

  	pr_info("Using PSCI v0.1 Function IDs from DT\n");

+	psci_ops.get_version = psci_0_1_get_version;
+
  	if (!of_property_read_u32(np, "cpu_suspend", &id)) {
  		psci_function_id[PSCI_FN_CPU_SUSPEND] = id;
  		psci_ops.cpu_suspend = psci_cpu_suspend;

-- 
Jazz is not dead. It just smells funny...

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