Re: [PATCH v14 1/4] xen/arm: Implement PSCI SYSTEM_SUSPEND call for guests

["Orzel, Michal" <michal.orzel@xxxxxxx>]

On 18/11/2025 16:37, Mykola Kvach wrote:
> From: Mykola Kvach <mykola_kvach@xxxxxxxx>
> 
> Add support for the PSCI SYSTEM_SUSPEND function in the vPSCI interface,
> allowing guests to request suspend via the PSCI v1.0+ SYSTEM_SUSPEND call
> (both 32-bit and 64-bit variants).
> 
> Implementation details:
> - Add SYSTEM_SUSPEND function IDs to PSCI definitions
> - Trap and handle SYSTEM_SUSPEND in vPSCI
> - Allow only non-hardware domains to invoke SYSTEM_SUSPEND; return
>   PSCI_NOT_SUPPORTED for the hardware domain to avoid halting the system
>   in hwdom_shutdown() via domain_shutdown
> - Require all secondary VCPUs of the calling domain to be offline before
>   suspend, as mandated by the PSCI specification
> 
> The arch_domain_resume() function is an architecture-specific hook that is
> invoked during domain resume to perform any necessary setup or restoration
> steps required by the platform.
> 
> The new vpsci_vcpu_up_prepare() helper is called on the resume path to set up
> the vCPU context (such as entry point, some system regs and context ID) before
> resuming a suspended guest. This keeps ARM/vPSCI-specific logic out of common
> code and avoids intrusive changes to the generic resume flow.
> 
> Usage:
> 
> For Linux-based guests, suspend can be initiated with:
>     echo mem > /sys/power/state
> or via:
>     systemctl suspend
> 
> Resuming the guest is performed from control domain using:
>       xl resume <domain>
> 
> Signed-off-by: Mykola Kvach <mykola_kvach@xxxxxxxx>
> ---
> Changes in V14:
> - move arch_domain_resume to a separate header
> - avoid usage of typeof for context struct
> - moved error printing from domain_resume to arch_domain_resume
>   in order to simplify common parts of code
> - minor changes after review
> ---
>  xen/arch/arm/domain.c                 |  41 +++++++++
>  xen/arch/arm/include/asm/domain.h     |   2 +
>  xen/arch/arm/include/asm/perfc_defn.h |   1 +
>  xen/arch/arm/include/asm/psci.h       |   2 +
>  xen/arch/arm/include/asm/suspend.h    |  24 ++++++
>  xen/arch/arm/include/asm/vpsci.h      |   5 +-
>  xen/arch/arm/vpsci.c                  | 116 +++++++++++++++++++++-----
>  xen/common/domain.c                   |   5 ++
>  xen/include/xen/suspend.h             |  15 ++++
>  9 files changed, 189 insertions(+), 22 deletions(-)
>  create mode 100644 xen/arch/arm/include/asm/suspend.h
>  create mode 100644 xen/include/xen/suspend.h
> 
> diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
> index e36719bce4..3c0170480b 100644
> --- a/xen/arch/arm/domain.c
> +++ b/xen/arch/arm/domain.c
> @@ -12,6 +12,8 @@
>  #include <xen/softirq.h>
>  #include <xen/wait.h>
>  
> +#include <public/sched.h>
> +
>  #include <asm/arm64/sve.h>
>  #include <asm/cpuerrata.h>
>  #include <asm/cpufeature.h>
> @@ -24,10 +26,12 @@
>  #include <asm/platform.h>
>  #include <asm/procinfo.h>
>  #include <asm/regs.h>
> +#include <asm/suspend.h>
>  #include <asm/firmware/sci.h>
>  #include <asm/tee/tee.h>
>  #include <asm/vfp.h>
>  #include <asm/vgic.h>
> +#include <asm/vpsci.h>
>  #include <asm/vtimer.h>
>  
>  #include "vpci.h"
> @@ -885,6 +889,43 @@ void arch_domain_creation_finished(struct domain *d)
>      p2m_domain_creation_finished(d);
>  }
>  
> +int arch_domain_resume(struct domain *d)
> +{
> +    int rc;
> +    struct resume_info *ctx = &d->arch.resume_ctx;
> +
> +    if ( !d->is_shutting_down || d->shutdown_code != SHUTDOWN_suspend )
> +    {
> +        dprintk(XENLOG_WARNING,
> +                "%pd: Invalid domain state for resume: is_shutting_down=%d, 
> shutdown_code=%d\n",
These are bool and uint, so %u should be used.

> +                d, d->is_shutting_down, d->shutdown_code);
> +        return -EINVAL;
> +    }
> +
> +    /*
> +     * It is still possible to call domain_shutdown() with a suspend reason
> +     * via some hypercalls, such as SCHEDOP_shutdown or 
> SCHEDOP_remote_shutdown.
> +     * In these cases, the resume context will be empty.
> +     * This is not expected to cause any issues, so we just warn about the
> +     * situation and return without error, allowing the existing logic to
> +     * proceed as expected.
> +     */
> +    if ( !ctx->wake_cpu )
> +    {
> +        dprintk(XENLOG_INFO, "%pd: Wake CPU pointer context was not 
> provided\n",
> +                d);
> +        return 0;
> +    }
> +
> +    rc = vpsci_vcpu_up_prepare(ctx->wake_cpu , ctx->ep, ctx->cid);
> +    if ( rc )
> +        printk("%pd: Failed to resume domain (ret %d)\n", d, rc);
> +
> +    memset(ctx, 0, sizeof(*ctx));
> +
> +    return rc;
> +}
> +
>  static int is_guest_pv32_psr(uint32_t psr)
>  {
>      switch (psr & PSR_MODE_MASK)
> diff --git a/xen/arch/arm/include/asm/domain.h 
> b/xen/arch/arm/include/asm/domain.h
> index af3e168374..e637cb4de0 100644
> --- a/xen/arch/arm/include/asm/domain.h
> +++ b/xen/arch/arm/include/asm/domain.h
> @@ -5,6 +5,7 @@
>  #include <xen/timer.h>
>  #include <asm/page.h>
>  #include <asm/p2m.h>
> +#include <asm/suspend.h>
>  #include <asm/vfp.h>
>  #include <asm/mmio.h>
>  #include <asm/gic.h>
> @@ -126,6 +127,7 @@ struct arch_domain
>      void *sci_data;
>  #endif
>  
> +    struct resume_info resume_ctx;
>  }  __cacheline_aligned;
>  
>  struct arch_vcpu
> diff --git a/xen/arch/arm/include/asm/perfc_defn.h 
> b/xen/arch/arm/include/asm/perfc_defn.h
> index effd25b69e..8dfcac7e3b 100644
> --- a/xen/arch/arm/include/asm/perfc_defn.h
> +++ b/xen/arch/arm/include/asm/perfc_defn.h
> @@ -33,6 +33,7 @@ PERFCOUNTER(vpsci_system_reset,        "vpsci: 
> system_reset")
>  PERFCOUNTER(vpsci_cpu_suspend,         "vpsci: cpu_suspend")
>  PERFCOUNTER(vpsci_cpu_affinity_info,   "vpsci: cpu_affinity_info")
>  PERFCOUNTER(vpsci_features,            "vpsci: features")
> +PERFCOUNTER(vpsci_system_suspend,      "vpsci: system_suspend")
>  
>  PERFCOUNTER(vcpu_kick,                 "vcpu: notify other vcpu")
>  
> diff --git a/xen/arch/arm/include/asm/psci.h b/xen/arch/arm/include/asm/psci.h
> index 4780972621..48a93e6b79 100644
> --- a/xen/arch/arm/include/asm/psci.h
> +++ b/xen/arch/arm/include/asm/psci.h
> @@ -47,10 +47,12 @@ void call_psci_system_reset(void);
>  #define PSCI_0_2_FN32_SYSTEM_OFF          PSCI_0_2_FN32(8)
>  #define PSCI_0_2_FN32_SYSTEM_RESET        PSCI_0_2_FN32(9)
>  #define PSCI_1_0_FN32_PSCI_FEATURES       PSCI_0_2_FN32(10)
> +#define PSCI_1_0_FN32_SYSTEM_SUSPEND      PSCI_0_2_FN32(14)
>  
>  #define PSCI_0_2_FN64_CPU_SUSPEND         PSCI_0_2_FN64(1)
>  #define PSCI_0_2_FN64_CPU_ON              PSCI_0_2_FN64(3)
>  #define PSCI_0_2_FN64_AFFINITY_INFO       PSCI_0_2_FN64(4)
> +#define PSCI_1_0_FN64_SYSTEM_SUSPEND      PSCI_0_2_FN64(14)
>  
>  /* PSCI v0.2 affinity level state returned by AFFINITY_INFO */
>  #define PSCI_0_2_AFFINITY_LEVEL_ON      0
> diff --git a/xen/arch/arm/include/asm/suspend.h 
> b/xen/arch/arm/include/asm/suspend.h
> new file mode 100644
> index 0000000000..b991a94d5a
> --- /dev/null
> +++ b/xen/arch/arm/include/asm/suspend.h
> @@ -0,0 +1,24 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +#ifndef __ARM_SUSPEND_H__
There should be no double underscores in guards (see examples in CODING_STYLE)
> +#define __ARM_SUSPEND_H__
> +
> +struct resume_info {
> +    register_t ep;
> +    register_t cid;
> +    struct vcpu *wake_cpu;
> +};
> +
> +int arch_domain_resume(struct domain *d);
If possible, headers should be standalone, meaning you should include necessary
headers or forward declare what's missing.

> +
> +#endif /* __ARM_SUSPEND_H__ */
> +
> + /*
> +  * Local variables:
> +  * mode: C
> +  * c-file-style: "BSD"
> +  * c-basic-offset: 4
> +  * tab-width: 4
> +  * indent-tabs-mode: nil
> +  * End:
> +  */
> diff --git a/xen/arch/arm/include/asm/vpsci.h 
> b/xen/arch/arm/include/asm/vpsci.h
> index 0cca5e6830..d790ab3715 100644
> --- a/xen/arch/arm/include/asm/vpsci.h
> +++ b/xen/arch/arm/include/asm/vpsci.h
> @@ -23,12 +23,15 @@
>  #include <asm/psci.h>
>  
>  /* Number of function implemented by virtual PSCI (only 0.2 or later) */
> -#define VPSCI_NR_FUNCS  12
> +#define VPSCI_NR_FUNCS  14
>  
>  /* Functions handle PSCI calls from the guests */
>  bool do_vpsci_0_1_call(struct cpu_user_regs *regs, uint32_t fid);
>  bool do_vpsci_0_2_call(struct cpu_user_regs *regs, uint32_t fid);
>  
> +int vpsci_vcpu_up_prepare(struct vcpu *v, register_t entry_point,
> +                          register_t context_id);
> +
>  #endif /* __ASM_VPSCI_H__ */
>  
>  /*
> diff --git a/xen/arch/arm/vpsci.c b/xen/arch/arm/vpsci.c
> index 7ba9ccd94b..22c3a5f544 100644
> --- a/xen/arch/arm/vpsci.c
> +++ b/xen/arch/arm/vpsci.c
> @@ -10,32 +10,16 @@
>  
>  #include <public/sched.h>
>  
> -static int do_common_cpu_on(register_t target_cpu, register_t entry_point,
> -                            register_t context_id)
> +int vpsci_vcpu_up_prepare(struct vcpu *v, register_t entry_point,
> +                   register_t context_id)
NIT: incorrect parameter alignment

>  {
> -    struct vcpu *v;
> -    struct domain *d = current->domain;
> -    struct vcpu_guest_context *ctxt;
>      int rc;
> +    struct domain *d = v->domain;
>      bool is_thumb = entry_point & 1;
> -    register_t vcpuid;
> -
> -    vcpuid = vaffinity_to_vcpuid(target_cpu);
> -
> -    if ( (v = domain_vcpu(d, vcpuid)) == NULL )
> -        return PSCI_INVALID_PARAMETERS;
> -
> -    /* THUMB set is not allowed with 64-bit domain */
> -    if ( is_64bit_domain(d) && is_thumb )
> -        return PSCI_INVALID_ADDRESS;
> -
> -    if ( !test_bit(_VPF_down, &v->pause_flags) )
> -        return PSCI_ALREADY_ON;
> +    struct vcpu_guest_context *ctxt;
>  
>      if ( (ctxt = alloc_vcpu_guest_context()) == NULL )
> -        return PSCI_DENIED;
> -
> -    vgic_clear_pending_irqs(v);
> +        return -ENOMEM;
>  
>      memset(ctxt, 0, sizeof(*ctxt));
>      ctxt->user_regs.pc64 = (u64) entry_point;
> @@ -76,8 +60,37 @@ static int do_common_cpu_on(register_t target_cpu, 
> register_t entry_point,
>      free_vcpu_guest_context(ctxt);
>  
>      if ( rc < 0 )
> +        return rc;
> +
> +    return 0;
> +}
> +
> +static int do_common_cpu_on(register_t target_cpu, register_t entry_point,
> +                            register_t context_id)
> +{
> +    struct vcpu *v;
> +    struct domain *d = current->domain;
> +    int rc;
> +    bool is_thumb = entry_point & 1;
> +    register_t vcpuid;
> +
> +    vcpuid = vaffinity_to_vcpuid(target_cpu);
> +
> +    if ( (v = domain_vcpu(d, vcpuid)) == NULL )
> +        return PSCI_INVALID_PARAMETERS;
> +
> +    /* THUMB set is not allowed with 64-bit domain */
> +    if ( is_64bit_domain(d) && is_thumb )
> +        return PSCI_INVALID_ADDRESS;
> +
> +    if ( !test_bit(_VPF_down, &v->pause_flags) )
> +        return PSCI_ALREADY_ON;
> +
> +    rc = vpsci_vcpu_up_prepare(v, entry_point, context_id);
> +    if ( rc )
>          return PSCI_DENIED;
>  
> +    vgic_clear_pending_irqs(v);
>      vcpu_wake(v);
>  
>      return PSCI_SUCCESS;
> @@ -197,6 +210,48 @@ static void do_psci_0_2_system_reset(void)
>      domain_shutdown(d,SHUTDOWN_reboot);
>  }
>  
> +static int32_t do_psci_1_0_system_suspend(register_t epoint, register_t cid)
> +{
> +    int32_t rc;
> +    struct vcpu *v;
> +    struct domain *d = current->domain;
> +    bool is_thumb = epoint & 1;
> +
> +    /* THUMB set is not allowed with 64-bit domain */
> +    if ( is_64bit_domain(d) && is_thumb )
> +        return PSCI_INVALID_ADDRESS;
> +
> +    /* SYSTEM_SUSPEND is not supported for the hardware domain yet */
> +    if ( is_hardware_domain(d) )
> +        return PSCI_NOT_SUPPORTED;
> +
> +    /* Ensure that all CPUs other than the calling one are offline */
> +    domain_lock(d);
> +    for_each_vcpu ( d, v )
> +    {
> +        if ( v != current && is_vcpu_online(v) )
> +        {
> +            domain_unlock(d);
> +            return PSCI_DENIED;
> +        }
> +    }
> +    domain_unlock(d);
> +
> +    rc = domain_shutdown(d, SHUTDOWN_suspend);
> +    if ( rc )
> +        return PSCI_DENIED;
> +
> +    d->arch.resume_ctx.ep = epoint;
> +    d->arch.resume_ctx.cid = cid;
> +    d->arch.resume_ctx.wake_cpu = current;
> +
> +    gprintk(XENLOG_DEBUG,
> +            "SYSTEM_SUSPEND requested, epoint=0x%"PRIregister", 
> cid=0x%"PRIregister"\n",
NIT: %# is preffered over 0x%.

> +            epoint, cid);
> +
> +    return rc;
> +}
> +
>  static int32_t do_psci_1_0_features(uint32_t psci_func_id)
>  {
>      /* /!\ Ordered by function ID and not name */
> @@ -214,6 +269,8 @@ static int32_t do_psci_1_0_features(uint32_t psci_func_id)
>      case PSCI_0_2_FN32_SYSTEM_OFF:
>      case PSCI_0_2_FN32_SYSTEM_RESET:
>      case PSCI_1_0_FN32_PSCI_FEATURES:
> +    case PSCI_1_0_FN32_SYSTEM_SUSPEND:
> +    case PSCI_1_0_FN64_SYSTEM_SUSPEND:
>      case ARM_SMCCC_VERSION_FID:
>          return 0;
>      default:
> @@ -344,6 +401,23 @@ bool do_vpsci_0_2_call(struct cpu_user_regs *regs, 
> uint32_t fid)
>          return true;
>      }
>  
> +    case PSCI_1_0_FN32_SYSTEM_SUSPEND:
> +    case PSCI_1_0_FN64_SYSTEM_SUSPEND:
> +    {
> +        register_t epoint = PSCI_ARG(regs, 1);
> +        register_t cid = PSCI_ARG(regs, 2);
> +
> +        if ( fid == PSCI_1_0_FN32_SYSTEM_SUSPEND )
> +        {
> +            epoint &= GENMASK(31, 0);
> +            cid &= GENMASK(31, 0);
> +        }
> +
> +        perfc_incr(vpsci_system_suspend);
> +        PSCI_SET_RESULT(regs, do_psci_1_0_system_suspend(epoint, cid));
> +        return true;
> +    }
> +
>      default:
>          return false;
>      }
> diff --git a/xen/common/domain.c b/xen/common/domain.c
> index 775c339285..6410d32970 100644
> --- a/xen/common/domain.c
> +++ b/xen/common/domain.c
> @@ -26,6 +26,7 @@
>  #include <xen/hypercall.h>
>  #include <xen/delay.h>
>  #include <xen/shutdown.h>
> +#include <xen/suspend.h>
>  #include <xen/percpu.h>
>  #include <xen/multicall.h>
>  #include <xen/rcupdate.h>
> @@ -1363,6 +1364,9 @@ void domain_resume(struct domain *d)
>  
>      spin_lock(&d->shutdown_lock);
>  
> +    if ( arch_domain_resume(d) )
> +        goto fail;
> +
>      d->is_shutting_down = d->is_shut_down = 0;
>      d->shutdown_code = SHUTDOWN_CODE_INVALID;
>  
> @@ -1373,6 +1377,7 @@ void domain_resume(struct domain *d)
>          v->paused_for_shutdown = 0;
>      }
>  
> + fail:
>      spin_unlock(&d->shutdown_lock);
>  
>      domain_unpause(d);
> diff --git a/xen/include/xen/suspend.h b/xen/include/xen/suspend.h
> new file mode 100644
> index 0000000000..53f75fd6ad
> --- /dev/null
> +++ b/xen/include/xen/suspend.h
> @@ -0,0 +1,15 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +#ifndef __XEN_SUSPEND_H__
There should be no double underscores in guards

> +#define __XEN_SUSPEND_H__
> +
> +#if __has_include(<asm/suspend.h>)
> +#include <asm/suspend.h>
> +#else
> +static inline int arch_domain_resume(struct domain *d)
> +{
> +    return 0;
> +}
> +#endif
> +
Stray whiteline?

> +
> +#endif /* __XEN_SUSPEND_H__ */
Missing emacs block?

Did you run MISRA scan on this patch?

~Michal