[PATCH v4][PART 2 04/10] xen/arm: Prevent crash during disable_nonboot_cpus on suspend

[Mykola Kvach <xakep.amatop@xxxxxxxxx>]

From: Mykola Kvach <mykola_kvach@xxxxxxxx>

If we call disable_nonboot_cpus on ARM64 with system_state set
to SYS_STATE_suspend, the following assertion will be triggered:

```
(XEN) [   25.582712] Disabling non-boot CPUs ...
(XEN) [   25.587032] Assertion '!in_irq() && (local_irq_is_enabled() || 
num_online_cpus() <= 1)' failed at common/xmalloc_tlsf.c:714
[...]
(XEN) [   25.975069] Xen call trace:
(XEN) [   25.978353]    [<00000a000022e098>] xfree+0x130/0x1a4 (PC)
(XEN) [   25.984314]    [<00000a000022e08c>] xfree+0x124/0x1a4 (LR)
(XEN) [   25.990276]    [<00000a00002747d4>] release_irq+0xe4/0xe8
(XEN) [   25.996152]    [<00000a0000278588>] time.c#cpu_time_callback+0x44/0x60
(XEN) [   26.003150]    [<00000a000021d678>] notifier_call_chain+0x7c/0xa0
(XEN) [   26.009717]    [<00000a00002018e0>] 
cpu.c#cpu_notifier_call_chain+0x24/0x48
(XEN) [   26.017148]    [<00000a000020192c>] cpu.c#_take_cpu_down+0x28/0x34
(XEN) [   26.023801]    [<00000a0000201944>] cpu.c#take_cpu_down+0xc/0x18
(XEN) [   26.030281]    [<00000a0000225c5c>] 
stop_machine.c#stopmachine_action+0xbc/0xe4
(XEN) [   26.038057]    [<00000a00002264bc>] 
tasklet.c#do_tasklet_work+0xb8/0x100
(XEN) [   26.045229]    [<00000a00002268a4>] do_tasklet+0x68/0xb0
(XEN) [   26.051018]    [<00000a000026e120>] domain.c#idle_loop+0x7c/0x194
(XEN) [   26.057585]    [<00000a0000277e30>] start_secondary+0x21c/0x220
(XEN) [   26.063978]    [<00000a0000361258>] 00000a0000361258
```

This happens because before invoking take_cpu_down via the stop_machine_run
function on the target CPU, stop_machine_run requests
the STOPMACHINE_DISABLE_IRQ state on that CPU. Releasing memory in
the release_irq function then triggers the assertion:

/*
 * Heap allocations may need TLB flushes which may require IRQs to be
 * enabled (except when only 1 PCPU is online).
 */

This patch adds system state checks to guard calls to request_irq
and release_irq. These calls are now skipped when system_state is
SYS_STATE_{resume,suspend}, preventing unsafe operations during
suspend/resume handling.

Signed-off-by: Mykola Kvach <mykola_kvach@xxxxxxxx>
---
Changes in V4:
  - removed the prior tasklet-based workaround in favor of a more
    straightforward and safer solution
  - reworked the approach by adding explicit system state checks around
    request_irq and release_irq calls, skips these calls during suspend
    and resume states to avoid unsafe memory operations when IRQs are
    disabled
---
 xen/arch/arm/gic.c           |  6 ++++++
 xen/arch/arm/tee/ffa_notif.c |  2 +-
 xen/arch/arm/time.c          | 18 ++++++++++++------
 3 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index a018bd7715..9856cb1592 100644
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -388,6 +388,9 @@ void gic_dump_info(struct vcpu *v)
 
 void init_maintenance_interrupt(void)
 {
+    if ( system_state == SYS_STATE_resume )
+        return;
+
     request_irq(gic_hw_ops->info->maintenance_irq, 0, maintenance_interrupt,
                 "irq-maintenance", NULL);
 }
@@ -461,6 +464,9 @@ static int cpu_gic_callback(struct notifier_block *nfb,
     switch ( action )
     {
     case CPU_DYING:
+        if ( system_state == SYS_STATE_suspend )
+            break;
+
         /* This is reverting the work done in init_maintenance_interrupt */
         release_irq(gic_hw_ops->info->maintenance_irq, NULL);
         break;
diff --git a/xen/arch/arm/tee/ffa_notif.c b/xen/arch/arm/tee/ffa_notif.c
index 00efaf8f73..06f715a82b 100644
--- a/xen/arch/arm/tee/ffa_notif.c
+++ b/xen/arch/arm/tee/ffa_notif.c
@@ -347,7 +347,7 @@ void ffa_notif_init_interrupt(void)
 {
     int ret;
 
-    if ( notif_enabled && notif_sri_irq < NR_GIC_SGI )
+    if ( notif_enabled && notif_sri_irq < NR_GIC_SGI && system_state != 
SYS_STATE_resume )
     {
         /*
          * An error here is unlikely since the primary CPU has already
diff --git a/xen/arch/arm/time.c b/xen/arch/arm/time.c
index ad984fdfdd..b2e07ade43 100644
--- a/xen/arch/arm/time.c
+++ b/xen/arch/arm/time.c
@@ -320,10 +320,13 @@ void init_timer_interrupt(void)
     WRITE_SYSREG(CNTHCTL_EL2_EL1PCTEN, CNTHCTL_EL2);
     disable_physical_timers();
 
-    request_irq(timer_irq[TIMER_HYP_PPI], 0, htimer_interrupt,
-                "hyptimer", NULL);
-    request_irq(timer_irq[TIMER_VIRT_PPI], 0, vtimer_interrupt,
-                   "virtimer", NULL);
+    if ( system_state != SYS_STATE_resume )
+    {
+        request_irq(timer_irq[TIMER_HYP_PPI], 0, htimer_interrupt,
+                    "hyptimer", NULL);
+        request_irq(timer_irq[TIMER_VIRT_PPI], 0, vtimer_interrupt,
+                    "virtimer", NULL);
+    }
 
     check_timer_irq_cfg(timer_irq[TIMER_HYP_PPI], "hypervisor");
     check_timer_irq_cfg(timer_irq[TIMER_VIRT_PPI], "virtual");
@@ -338,8 +341,11 @@ static void deinit_timer_interrupt(void)
 {
     disable_physical_timers();
 
-    release_irq(timer_irq[TIMER_HYP_PPI], NULL);
-    release_irq(timer_irq[TIMER_VIRT_PPI], NULL);
+    if ( system_state != SYS_STATE_suspend )
+    {
+        release_irq(timer_irq[TIMER_HYP_PPI], NULL);
+        release_irq(timer_irq[TIMER_VIRT_PPI], NULL);
+    }
 }
 
 /* Wait a set number of microseconds */
-- 
2.48.1