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

[Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>]

On 2025-11-19 12:00, Mykola Kvach wrote:
> Hi Michal,
>
> Thanks for your review.
>
> On Wed, Nov 19, 2025 at 10:48 AM Orzel, Michal <michal.orzel@xxxxxxx> 
> wrote:
> > 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.
> ack
>
> > > +                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)
> I had initially followed the style used by some of the existing headers
> in this directory, which still use guards with double underscores.
>
> I'll remove underscores in the next series.
>
> > > +#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.
> Thanks for the comment.
>
> My initial intention was to avoid adding new dependencies from asm
> headers to higher-level Xen headers, so I did not include e.g.
> <xen/sched.h> directly here. In this header we only need pointers to
> struct domain and struct vcpu, we never dereference them, so forward
> declarations would be sufficient to make it standalone.
>
> I also noticed that some existing asm headers in this directory do
> include higher-level Xen headers, so both patterns exist in the tree.
>
> If you prefer, I can either:
>   - add forward declarations
>
>       struct domain;
>       struct vcpu;
>
>     at the top of this header and keep the full includes in the .c
>     files that actually dereference these types, or
>
>   - include the appropriate Xen header(s) directly in this header.
>
> Personally I slightly prefer the forward-declaration approach to keep
> this header lightweight and avoid tightening the layering, but I am
> happy to follow your preference.
>
> > > +
> > > +#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
> ack
>
> > >  {
> > > -    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%.
> ack
>
> > > +            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
> I initially followed the style used by the existing headers in this
> directory, which still have include guards with double underscores.
>
> You are right that this does not match CODING_STYLE examples.
> I will update this header to use a proper guard name.
>
> > > +#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?
> will drop
>
> > > +
> > > +#endif /* __XEN_SUSPEND_H__ */
> > Missing emacs block?
> It is permitted but isn't necessary as far as know,
> but if it needed here per your opinion I'll add it
> just let me know
>
> > Did you run MISRA scan on this patch?
> Yes, I ran it with:
>
>   ./xen/scripts/xen-analysis.py \
>       --run-cppcheck --cppcheck-misra --cppcheck-html -- \
>       XEN_TARGET_ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu-
>
> The analysis did not report any new MISRA violations in the code
> touched by this patch.
This just runs cppcheck, which has many false negatives, but the 
upstream analysis should be done using ECLAIR with GitLab pipelines
> > ~Michal
> Best regards,
> Mykola
--
Nicola Vetrini, B.Sc.
Software Engineer
BUGSENG (https://bugseng.com)
LinkedIn: https://www.linkedin.com/in/nicola-vetrini-a42471253