xen/arm: Implement PSCI SYSTEM_SUSPEND call for guests

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
- Reject SYSTEM_SUSPEND for the hardware domain to avoid host shutdown
- Require all secondary VCPUs to be offline before suspend
- Split arch_set_info_guest() into arch_vcpu_validate_guest_context() and
  arch_vcpu_apply_guest_context() for reuse by vPSCI
- Add vpsci_build_guest_context() helper and store prevalidated context in
  resume_ctx; resume applies it and frees it
- Add 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.

Usage:

For Linux-based guests, suspend can be initiated with:
    echo mem > /sys/power/state
or via:
    systemctl suspend

Resume from control domain:
      xl resume <domain>

Signed-off-by: Mykola Kvach <mykola_kvach@epam.com>
Reviewed-by: Michal Orzel <michal.orzel@amd.com>

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"
@@ -770,8 +774,18 @@ int arch_domain_teardown(struct domain *d)
     return 0;
 }
 
+static void resume_ctx_reset(struct resume_info *ctx)
+{
+    if ( ctx->ctxt )
+        free_vcpu_guest_context(ctx->ctxt);
+
+    memset(ctx, 0, sizeof(*ctx));
+}
+
 void arch_domain_destroy(struct domain *d)
 {
+    resume_ctx_reset(&d->arch.resume_ctx);
+
     tee_free_domain_ctx(d);
     /* IOMMU page table is shared with P2M, always call
      * iommu_domain_destroy() before p2m_final_teardown().
@@ -806,6 +820,28 @@ void arch_domain_creation_finished(struct domain *d)
     p2m_domain_creation_finished(d);
 }
 
+void arch_domain_resume(struct domain *d)
+{
+    struct resume_info *ctx = &d->arch.resume_ctx;
+
+    /*
+     * 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, so there is no
+     * suspend-specific state to restore.
+     */
+    if ( !ctx->wake_cpu )
+        return;
+
+    ASSERT(d->shutdown_code == SHUTDOWN_suspend);
+
+    domain_lock(d);
+    arch_vcpu_apply_guest_context(ctx->wake_cpu, ctx->ctxt);
+    domain_unlock(d);
+
+    resume_ctx_reset(ctx);
+}
+
 static int is_guest_pv32_psr(uint32_t psr)
 {
     switch (psr & PSR_MODE_MASK)
@@ -848,15 +884,32 @@ static int is_guest_pv64_psr(uint64_t psr)
 }
 #endif
 
+void arch_vcpu_apply_guest_context(struct vcpu *v,
+                                   const struct vcpu_guest_context *ctxt)
+{
+    vcpu_regs_user_to_hyp(v, &ctxt->user_regs);
+
+    v->arch.sctlr = ctxt->sctlr;
+    v->arch.ttbr0 = ctxt->ttbr0;
+    v->arch.ttbr1 = ctxt->ttbr1;
+    v->arch.ttbcr = ctxt->ttbcr;
+
+    v->is_initialised = 1;
+
+    if ( ctxt->flags & VGCF_online )
+        clear_bit(_VPF_down, &v->pause_flags);
+    else
+        set_bit(_VPF_down, &v->pause_flags);
+}
+
 /*
  * Initialise vCPU state. The context may be supplied by an external entity, so
  * we need to validate it.
  */
-int arch_set_info_guest(
-    struct vcpu *v, vcpu_guest_context_u c)
+int arch_vcpu_validate_guest_context(const struct vcpu *v,
+                                     const struct vcpu_guest_context *ctxt)
 {
-    struct vcpu_guest_context *ctxt = c.nat;
-    struct vcpu_guest_core_regs *regs = &c.nat->user_regs;
+    const struct vcpu_guest_core_regs *regs = &ctxt->user_regs;
 
     if ( is_32bit_domain(v->domain) )
     {
@@ -885,19 +938,24 @@ int arch_set_info_guest(
     }
 #endif
 
-    vcpu_regs_user_to_hyp(v, regs);
+    return 0;
+}
 
-    v->arch.sctlr = ctxt->sctlr;
-    v->arch.ttbr0 = ctxt->ttbr0;
-    v->arch.ttbr1 = ctxt->ttbr1;
-    v->arch.ttbcr = ctxt->ttbcr;
+/*
+ * Initialise vCPU state. The context may be supplied by an external entity, so
+ * we need to validate it.
+ */
+int arch_set_info_guest(
+    struct vcpu *v, vcpu_guest_context_u c)
+{
+    struct vcpu_guest_context *ctxt = c.nat;
+    int rc;
 
-    v->is_initialised = 1;
+    rc = arch_vcpu_validate_guest_context(v, ctxt);
+    if ( rc )
+        return rc;
 
-    if ( ctxt->flags & VGCF_online )
-        clear_bit(_VPF_down, &v->pause_flags);
-    else
-        set_bit(_VPF_down, &v->pause_flags);
+    arch_vcpu_apply_guest_context(v, ctxt);
 
     return 0;
 }

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
@@ -290,6 +292,11 @@ static inline register_t vcpuid_to_vaffinity(unsigned int vcpuid)
     return vaff;
 }
 
+int arch_vcpu_validate_guest_context(const struct vcpu *v,
+                                     const struct vcpu_guest_context *ctxt);
+void arch_vcpu_apply_guest_context(struct vcpu *v,
+                                   const struct vcpu_guest_context *ctxt);
+
 static inline struct vcpu_guest_context *alloc_vcpu_guest_context(void)
 {
     return xmalloc(struct vcpu_guest_context);

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")
 

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

xen/arch/arm/include/asm/suspend.h

@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef ARM_SUSPEND_H
+#define ARM_SUSPEND_H
+
+struct domain;
+struct vcpu;
+struct vcpu_guest_context;
+
+struct resume_info {
+    struct vcpu_guest_context *ctxt;
+    struct vcpu *wake_cpu;
+};
+
+void arch_domain_resume(struct domain *d);
+
+#endif /* ARM_SUSPEND_H */
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */

xen/arch/arm/include/asm/vpsci.h

@@ -23,7 +23,7 @@
 #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);

xen/arch/arm/vpsci.c

@@ -4,38 +4,24 @@
 #include <xen/types.h>
 
 #include <asm/current.h>
+#include <asm/domain.h>
 #include <asm/vgic.h>
 #include <asm/vpsci.h>
 #include <asm/event.h>
 
 #include <public/sched.h>
 
-static int do_common_cpu_on(register_t target_cpu, register_t entry_point,
-                            register_t context_id)
+static int vpsci_build_guest_context(struct vcpu *v, register_t entry_point,
+                                     register_t context_id,
+                                     struct vcpu_guest_context **out)
 {
-    struct vcpu *v;
-    struct domain *d = current->domain;
+    bool is_thumb = entry_point & 1;
     struct vcpu_guest_context *ctxt;
     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;
-
-    if ( (ctxt = alloc_vcpu_guest_context()) == NULL )
-        return PSCI_DENIED;
-
-    vgic_clear_pending_irqs(v);
+    ctxt = alloc_vcpu_guest_context();
+    if ( ctxt == NULL )
+        return -ENOMEM;
 
     memset(ctxt, 0, sizeof(*ctxt));
     ctxt->user_regs.pc64 = (u64) entry_point;
@@ -48,7 +34,7 @@ static int do_common_cpu_on(register_t target_cpu, register_t entry_point,
      * x0/r0_usr are always updated because for PSCI 0.1 the general
      * purpose registers are undefined upon CPU_on.
      */
-    if ( is_32bit_domain(d) )
+    if ( is_32bit_domain(v->domain) )
     {
         ctxt->user_regs.cpsr = PSR_GUEST32_INIT;
         /* Start the VCPU with THUMB set if it's requested by the kernel */
@@ -69,15 +55,51 @@ static int do_common_cpu_on(register_t target_cpu, register_t entry_point,
 #endif
     ctxt->flags = VGCF_online;
 
+    rc = arch_vcpu_validate_guest_context(v, ctxt);
+    if ( rc )
+    {
+        free_vcpu_guest_context(ctxt);
+        return rc;
+    }
+
+    *out = ctxt;
+    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;
+    struct vcpu_guest_context *ctxt = NULL;
+    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_build_guest_context(v, entry_point, context_id, &ctxt);
+    if ( rc < 0 )
+        return PSCI_DENIED;
+
+    vgic_clear_pending_irqs(v);
+
     domain_lock(d);
-    rc = arch_set_info_guest(v, ctxt);
+    arch_vcpu_apply_guest_context(v, ctxt);
     domain_unlock(d);
 
     free_vcpu_guest_context(ctxt);
 
-    if ( rc < 0 )
-        return PSCI_DENIED;
-
     vcpu_wake(v);
 
     return PSCI_SUCCESS;
@@ -197,6 +219,56 @@ 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_guest_context *ctxt;
+    struct vcpu *v;
+    struct domain *d = current->domain;
+    bool is_thumb = epoint & 1;
+    struct resume_info *rctx = &d->arch.resume_ctx;
+
+    /* 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 = vpsci_build_guest_context(current, epoint, cid, &ctxt);
+    if ( rc )
+        return PSCI_DENIED;
+
+    rc = domain_shutdown(d, SHUTDOWN_suspend);
+    if ( rc )
+    {
+        free_vcpu_guest_context(ctxt);
+        return PSCI_DENIED;
+    }
+
+    rctx->ctxt = ctxt;
+    rctx->wake_cpu = current;
+
+    gprintk(XENLOG_DEBUG,
+            "SYSTEM_SUSPEND requested, epoint=%#"PRIregister", cid=%#"PRIregister"\n",
+            epoint, cid);
+
+    return rc;
+}
+
 static int32_t do_psci_1_0_features(uint32_t psci_func_id)
 {
     /* /!\ Ordered by function ID and not name */
@@ -216,6 +288,9 @@ static int32_t do_psci_1_0_features(uint32_t psci_func_id)
     case PSCI_1_0_FN32_PSCI_FEATURES:
     case ARM_SMCCC_VERSION_FID:
         return 0;
+    case PSCI_1_0_FN32_SYSTEM_SUSPEND:
+    case PSCI_1_0_FN64_SYSTEM_SUSPEND:
+        return is_hardware_domain(current->domain) ? PSCI_NOT_SUPPORTED : 0;
     default:
         return PSCI_NOT_SUPPORTED;
     }
@@ -344,6 +419,23 @@ 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;
     }

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>
@@ -1435,6 +1436,9 @@ void domain_resume(struct domain *d)
     spin_lock(&d->shutdown_lock);
 
     d->is_shutting_down = d->is_shut_down = 0;
+
+    arch_domain_resume(d);
+
     d->shutdown_code = SHUTDOWN_CODE_INVALID;
 
     for_each_vcpu ( d, v )

xen/include/xen/suspend.h

@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef XEN_SUSPEND_H
+#define XEN_SUSPEND_H
+
+#if __has_include(<asm/suspend.h>)
+#include <asm/suspend.h>
+#else
+static inline void arch_domain_resume(struct domain *d) {}
+#endif
+
+#endif /* XEN_SUSPEND_H */
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */