Re: [PATCH v12 11/13] xen/arm: Implement PSCI SYSTEM_SUSPEND call (host interface)

[Bertrand Marquis <Bertrand.Marquis@arm.com>]

Hi Mykola,

> On 27 Aug 2026, at 16:31, Mykola Kvach <mykola_kvach@epam.com> wrote:
> 
> From: Mirela Simonovic <mirela.simonovic@aggios.com>
> 
> Invoke PSCI SYSTEM_SUSPEND to finalize Xen's suspend sequence on ARM64
> platforms. Pass the Xen resume entry point (hyp_resume) to EL3 together
> with a zero context ID, matching Linux.
> 
> This patch wires up only the host-side PSCI SYSTEM_SUSPEND invocation.
> The resume trampoline and context restore are provided by earlier patches
> in the series.
> 
> Only enable this path when CONFIG_SYSTEM_SUSPEND is set and PSCI
> advertises SYSTEM_SUSPEND via PSCI_FEATURES.
> 
> Signed-off-by: Mirela Simonovic <mirela.simonovic@aggios.com>
> Signed-off-by: Saeed Nowshadi <saeed.nowshadi@xilinx.com>
> Signed-off-by: Mykyta Poturai <mykyta_poturai@epam.com>
> Signed-off-by: Mykola Kvach <mykola_kvach@epam.com>
> Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>
> ---
> Changes in v9:
> - cache SYSTEM_SUSPEND support using PSCI_FEATURES and gate the host call
>  on the cached capability
> - keep the cached SYSTEM_SUSPEND capability read-only after init
> - log whether firmware reports SYSTEM_SUSPEND support
> - pass an explicit zero context ID in the SYSTEM_SUSPEND call
> - drop the stale note claiming hyp_resume is still a stub
> ---
> xen/arch/arm/include/asm/psci.h |  1 +
> xen/arch/arm/psci.c             | 31 ++++++++++++++++++++++++++++++-
> 2 files changed, 31 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/arch/arm/include/asm/psci.h b/xen/arch/arm/include/asm/psci.h
> index 48a93e6b79..bb3c73496e 100644
> --- a/xen/arch/arm/include/asm/psci.h
> +++ b/xen/arch/arm/include/asm/psci.h
> @@ -23,6 +23,7 @@ int call_psci_cpu_on(int cpu);
> void call_psci_cpu_off(void);
> void call_psci_system_off(void);
> void call_psci_system_reset(void);
> +int call_psci_system_suspend(void);
> 
> /* Range of allocated PSCI function numbers */
> #define PSCI_FNUM_MIN_VALUE                 _AC(0,U)
> diff --git a/xen/arch/arm/psci.c b/xen/arch/arm/psci.c
> index b6860a7760..e05dae1133 100644
> --- a/xen/arch/arm/psci.c
> +++ b/xen/arch/arm/psci.c
> @@ -17,23 +17,27 @@
> #include <asm/cpufeature.h>
> #include <asm/psci.h>
> #include <asm/acpi.h>
> +#include <asm/suspend.h>
> 
> /*
>  * While a 64-bit OS can make calls with SMC32 calling conventions, for
>  * some calls it is necessary to use SMC64 to pass or return 64-bit values.
> - * For such calls PSCI_0_2_FN_NATIVE(x) will choose the appropriate
> + * For such calls PSCI_*_FN_NATIVE(x) will choose the appropriate
>  * (native-width) function ID.
>  */
> #ifdef CONFIG_ARM_64
> #define PSCI_0_2_FN_NATIVE(name)    PSCI_0_2_FN64_##name
> +#define PSCI_1_0_FN_NATIVE(name)    PSCI_1_0_FN64_##name
> #else
> #define PSCI_0_2_FN_NATIVE(name)    PSCI_0_2_FN32_##name
> +#define PSCI_1_0_FN_NATIVE(name)    PSCI_1_0_FN32_##name
> #endif
> 
> uint32_t psci_ver;
> uint32_t smccc_ver;
> 
> static uint32_t psci_cpu_on_nr;
> +static bool __ro_after_init has_psci_system_suspend;
> 
> #define PSCI_RET(res)   ((int32_t)(res).a0)
> 
> @@ -60,6 +64,25 @@ void call_psci_cpu_off(void)
>     }
> }
> 
> +int call_psci_system_suspend(void)
> +{
> +#ifdef CONFIG_SYSTEM_SUSPEND
> +    struct arm_smccc_res res;
> +
> +    if ( !has_psci_system_suspend )
> +        return PSCI_NOT_SUPPORTED;
> +
> +    /* Context ID is unused for the Xen resume path. */
> +    arm_smccc_smc(PSCI_1_0_FN_NATIVE(SYSTEM_SUSPEND), __pa(hyp_resume), 0,
> +                  &res);

Since this series was sent, arm_smccc_smc() has been changed to return
the result directly instead of writing it through a result pointer.

You need to update this call.

Cheers
Bertrand


> +    return PSCI_RET(res);
> +#else
> +    dprintk(XENLOG_WARNING,
> +            "SYSTEM_SUSPEND not supported (CONFIG_SYSTEM_SUSPEND disabled)\n");
> +    return PSCI_NOT_SUPPORTED;
> +#endif
> +}
> +
> void call_psci_system_off(void)
> {
>     if ( psci_ver > PSCI_VERSION(0, 1) )
> @@ -223,9 +246,15 @@ int __init psci_init(void)
> 
>     psci_init_smccc();
> 
> +    has_psci_system_suspend =
> +        psci_features(PSCI_1_0_FN_NATIVE(SYSTEM_SUSPEND)) == 0;
> +
>     printk(XENLOG_INFO "Using PSCI v%u.%u\n",
>            PSCI_VERSION_MAJOR(psci_ver), PSCI_VERSION_MINOR(psci_ver));
> 
> +    printk(XENLOG_DEBUG "PSCI SYSTEM_SUSPEND is %ssupported by firmware\n",
> +           has_psci_system_suspend ? "" : "not ");
> +
>     return 0;
> }
> 
> -- 
> 2.43.0
>