x86/irq: Handle spurious interrupt after shutdown gracefully

BugLink: https://bugs.launchpad.net/bugs/1839036
commit b7107a67f0d125459fe41f86e8079afd1a5e0b15 upstream

Since the rework of the vector management, warnings about spurious
interrupts have been reported. Robert provided some more information and
did an initial analysis. The following situation leads to these warnings:

   CPU 0                  CPU 1               IO_APIC

                                              interrupt is raised
                                              sent to CPU1
			  Unable to handle
			  immediately
			  (interrupts off,
			   deep idle delay)
   mask()
   ...
   free()
     shutdown()
     synchronize_irq()
     clear_vector()
                          do_IRQ()
                            -> vector is clear

Before the rework the vector entries of legacy interrupts were statically
assigned and occupied precious vector space while most of them were
unused. Due to that the above situation was handled silently because the
vector was handled and the core handler of the assigned interrupt
descriptor noticed that it is shut down and returned.

While this has been usually observed with legacy interrupts, this situation
is not limited to them. Any other interrupt source, e.g. MSI, can cause the
same issue.

After adding proper synchronization for level triggered interrupts, this
can only happen for edge triggered interrupts where the IO-APIC obviously
cannot provide information about interrupts in flight.

While the spurious warning is actually harmless in this case it worries
users and driver developers.

Handle it gracefully by marking the vector entry as VECTOR_SHUTDOWN instead
of VECTOR_UNUSED when the vector is freed up.

If that above late handling happens the spurious detector will not complain
and switch the entry to VECTOR_UNUSED. Any subsequent spurious interrupt on
that line will trigger the spurious warning as before.

Fixes: 464d12309e1b ("x86/vector: Switch IOAPIC to global reservation mode")
Reported-by: Robert Hodaszi <Robert.Hodaszi@digi.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>-
Tested-by: Robert Hodaszi <Robert.Hodaszi@digi.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Link: https://lkml.kernel.org/r/20190628111440.459647741@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/arch/x86/include/asm/hw_irq.h b/arch/x86/include/asm/hw_irq.h
index 32e666e1231e77f128252b2f9354f708081cafdb..626e1ac6516ee63628765d83187011afff887d49 100644 (file)
--- a/arch/x86/include/asm/hw_irq.h
+++ b/arch/x86/include/asm/hw_irq.h
@@ -151,7 +151,8 @@ extern char irq_entries_start[];
 #endif
 
 #define VECTOR_UNUSED          NULL
-#define VECTOR_RETRIGGERED     ((void *)~0UL)
+#define VECTOR_SHUTDOWN                ((void *)~0UL)
+#define VECTOR_RETRIGGERED     ((void *)~1UL)
 
 typedef struct irq_desc* vector_irq_t[NR_VECTORS];
 DECLARE_PER_CPU(vector_irq_t, vector_irq);

diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
index dc03c79c2f7b6aa49ca0093207ecec090493441f..ad04b0528adc97b44ec712f6d31889da6848a9a3 100644 (file)
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -351,7 +351,7 @@ static void clear_irq_vector(struct irq_data *irqd)
        trace_vector_clear(irqd->irq, vector, apicd->cpu, apicd->prev_vector,
                           apicd->prev_cpu);
 
-       per_cpu(vector_irq, apicd->cpu)[vector] = VECTOR_UNUSED;
+       per_cpu(vector_irq, apicd->cpu)[vector] = VECTOR_SHUTDOWN;
        irq_matrix_free(vector_matrix, apicd->cpu, vector, managed);
        apicd->vector = 0;
 
@@ -360,7 +360,7 @@ static void clear_irq_vector(struct irq_data *irqd)
        if (!vector)
                return;
 
-       per_cpu(vector_irq, apicd->prev_cpu)[vector] = VECTOR_UNUSED;
+       per_cpu(vector_irq, apicd->prev_cpu)[vector] = VECTOR_SHUTDOWN;
        irq_matrix_free(vector_matrix, apicd->prev_cpu, vector, managed);
        apicd->prev_vector = 0;
        apicd->move_in_progress = 0;

diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 92411e5809fb169468b9d63bd8a379af7b64d2e6..e8312828d2c25154fa3b39a26fb7e106abf97347 100644 (file)
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -230,7 +230,7 @@ __visible unsigned int __irq_entry do_IRQ(struct pt_regs *regs)
        if (!handle_irq(desc, regs)) {
                ack_APIC_irq();
 
-               if (desc != VECTOR_RETRIGGERED) {
+               if (desc != VECTOR_RETRIGGERED && desc != VECTOR_SHUTDOWN) {
                        pr_emerg_ratelimited("%s: %d.%d No irq handler for vector\n",
                                             __func__, smp_processor_id(),
                                             vector);