Re: [PATCH v8 12/13] xen/arm: Implement PSCI SYSTEM_SUSPEND call (host interface)

[Luca Fancellu <Luca.Fancellu@xxxxxxx>]

Hi Mykola,

> On 2 Apr 2026, at 11:45, Mykola Kvach <xakep.amatop@xxxxxxxxx> wrote:
> 
> From: Mirela Simonovic <mirela.simonovic@xxxxxxxxxx>
> 
> Invoke PSCI SYSTEM_SUSPEND to finalize Xen's suspend sequence on ARM64 
> platforms.
> Pass the resume entry point (hyp_resume) as the first argument to EL3. The 
> resume
> handler is currently a stub and will be implemented later in assembly. Ignore 
> the
> context ID argument, as is done in Linux.
> 
> Only enable this path when CONFIG_SYSTEM_SUSPEND is set and
> PSCI version is >= 1.0.
> 
> Signed-off-by: Mirela Simonovic <mirela.simonovic@xxxxxxxxxx>
> Signed-off-by: Saeed Nowshadi <saeed.nowshadi@xxxxxxxxxx>
> Signed-off-by: Mykyta Poturai <mykyta_poturai@xxxxxxxx>
> Signed-off-by: Mykola Kvach <mykola_kvach@xxxxxxxx>
> ---
> Changes in v7:
> - no changes
> ---
> xen/arch/arm/include/asm/psci.h |  1 +
> xen/arch/arm/psci.c             | 23 ++++++++++++++++++++++-
> 2 files changed, 23 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..c9d126b195 100644
> --- a/xen/arch/arm/psci.c
> +++ b/xen/arch/arm/psci.c
> @@ -17,17 +17,20 @@
> #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;
> @@ -60,6 +63,24 @@ void call_psci_cpu_off(void)
>     }
> }
> 
> +int call_psci_system_suspend(void)
> +{
> +#ifdef CONFIG_SYSTEM_SUSPEND
> +    struct arm_smccc_res res;
> +
> +    if ( psci_ver < PSCI_VERSION(1, 0) )
> +        return PSCI_NOT_SUPPORTED;
> +
> +    /* 2nd argument (context ID) is not used */
> +    arm_smccc_smc(PSCI_1_0_FN_NATIVE(SYSTEM_SUSPEND), __pa(hyp_resume), 
> &res);

I think Linux is passing 0 as context ID, probably to mark that it’s not used, 
I think we should do the
same

> +    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) )
> 

Cheers,
Luca