[xen staging] xen/arm: Defer request_irq on secondary CPUs after local_irq_enable

[patchbot@xxxxxxx]

commit 0086803a0dfb2ac80c2483cde2fbb87c8df6d254
Author:     Henry Wang <Henry.Wang@xxxxxxx>
AuthorDate: Sat May 7 10:54:33 2022 +0800
Commit:     Julien Grall <jgrall@xxxxxxxxxx>
CommitDate: Mon May 16 18:05:34 2022 +0100

    xen/arm: Defer request_irq on secondary CPUs after local_irq_enable
    
    With the enhanced ASSERT_ALLOC_CONTEXT, calling request_irq before
    local_irq_enable on secondary cores will lead to
    
    (XEN) Xen call trace:
    (XEN) [<000000000021d86c>] alloc_xenheap_pages+0x74/0x194 (PC)
    (XEN) [<000000000021d864>] alloc_xenheap_pages+0x6c/0x194 (LR)
    (XEN) [<0000000000229e90>] xmalloc_tlsf.c#xmalloc_pool_get+0x1c/0x28
    (XEN) [<000000000022a270>] xmem_pool_alloc+0x21c/0x448
    (XEN) [<000000000022a8dc>] _xmalloc+0x8c/0x290
    (XEN) [<000000000026b57c>] request_irq+0x40/0xb8
    (XEN) [<0000000000272780>] init_timer_interrupt+0x74/0xcc
    (XEN) [<000000000027212c>] start_secondary+0x1b4/0x238
    (XEN) [<0000000084000200>] 0000000084000200
    (XEN)
    (XEN)
    (XEN) ****************************************
    (XEN) Panic on CPU 4:
    (XEN) Assertion '!in_irq() && (local_irq_is_enabled() ||
    num_online_cpus() <= 1)' failed at common/page_alloc.c:2212
    (XEN) ****************************************
    
    on systems without a big enough pool for xmalloc() to cater the
    requested size.
    
    Moving the call of request_irq() past local_irq_enable() on
    secondary cores will make sure the assertion condition in
    alloc_xenheap_pages(), i.e. !in_irq && local_irq_enabled() is
    satisfied. It is also safe because the timer and GIC maintenance
    interrupt will not be used until the CPU is fully online.
    
    Reported-by: Wei Chen <Wei.Chen@xxxxxxx>
    Suggested-by: Julien Grall <jgrall@xxxxxxxxxx>
    Signed-off-by: Henry Wang <Henry.Wang@xxxxxxx>
    Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
---
 xen/arch/arm/smpboot.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/xen/arch/arm/smpboot.c b/xen/arch/arm/smpboot.c
index 7bfd0a73a7..9bb32a301a 100644
--- a/xen/arch/arm/smpboot.c
+++ b/xen/arch/arm/smpboot.c
@@ -361,9 +361,6 @@ void start_secondary(void)
 
     init_secondary_IRQ();
 
-    init_maintenance_interrupt();
-    init_timer_interrupt();
-
     set_current(idle_vcpu[cpuid]);
 
     setup_cpu_sibling_map(cpuid);
@@ -380,6 +377,15 @@ void start_secondary(void)
     cpumask_set_cpu(cpuid, &cpu_online_map);
 
     local_irq_enable();
+
+    /*
+     * Calling request_irq() after local_irq_enable() on secondary cores
+     * will make sure the assertion condition in alloc_xenheap_pages(),
+     * i.e. !in_irq && local_irq_enabled() is satisfied.
+     */
+    init_maintenance_interrupt();
+    init_timer_interrupt();
+
     local_abort_enable();
 
     check_local_cpu_errata();
--
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