[xen stable-4.18] x86/i8259: do not assume interrupts always target CPU0

[patchbot@xxxxxxx]

commit fcb1016bbd476e17c72b1837ae2a3eaac517fa52
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Thu Nov 23 12:12:47 2023 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Nov 23 12:12:47 2023 +0100

    x86/i8259: do not assume interrupts always target CPU0
    
    Sporadically we have seen the following during AP bringup on AMD platforms
    only:
    
    microcode: CPU59 updated from revision 0x830107a to 0x830107a, date = 
2023-05-17
    microcode: CPU60 updated from revision 0x830104d to 0x830107a, date = 
2023-05-17
    CPU60: No irq handler for vector 27 (IRQ -2147483648)
    microcode: CPU61 updated from revision 0x830107a to 0x830107a, date = 
2023-05-17
    
    This is similar to the issue raised on Linux commit 36e9e1eab777e, where 
they
    observed i8259 (active) vectors getting delivered to CPUs different than 0.
    
    On AMD or Hygon platforms adjust the target CPU mask of i8259 interrupt
    descriptors to contain all possible CPUs, so that APs will reserve the 
vector
    at startup if any legacy IRQ is still delivered through the i8259.  Note 
that
    if the IO-APIC takes over those interrupt descriptors the CPU mask will be
    reset.
    
    Spurious i8259 interrupt vectors however (IRQ7 and IRQ15) can be injected 
even
    when all i8259 pins are masked, and hence would need to be handled on all 
CPUs.
    
    Continue to reserve PIC vectors on CPU0 only, but do check for such spurious
    interrupts on all CPUs if the vendor is AMD or Hygon.  Note that once the
    vectors get used by devices detecting PIC spurious interrupts will no 
longer be
    possible, however the device driver should be able to cope with spurious
    interrupts.  Such PIC spurious interrupts occurring when the vector is in 
use
    by a local APIC routed source will lead to an extra EOI, which might
    unintentionally clear a different vector from ISR.  Note this is already the
    current behavior, so assume it's infrequent enough to not cause real issues.
    
    Finally, adjust the printed message to display the CPU where the spurious
    interrupt has been received, so it looks like:
    
    microcode: CPU1 updated from revision 0x830107a to 0x830107a, date = 
2023-05-17
    cpu1: spurious 8259A interrupt: IRQ7
    microcode: CPU2 updated from revision 0x830104d to 0x830107a, date = 
2023-05-17
    
    Amends: 3fba06ba9f8b ('x86/IRQ: re-use legacy vector ranges on APs')
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    master commit: 87f37449d586b4d407b75235bb0a171e018e25ec
    master date: 2023-11-02 10:50:59 +0100
---
 xen/arch/x86/i8259.c | 21 +++++++++++++++++++--
 xen/arch/x86/irq.c   | 11 ++++++++++-
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/i8259.c b/xen/arch/x86/i8259.c
index ed9f55abe5..e0fa1f96b4 100644
--- a/xen/arch/x86/i8259.c
+++ b/xen/arch/x86/i8259.c
@@ -222,7 +222,8 @@ static bool _mask_and_ack_8259A_irq(unsigned int irq)
         is_real_irq = false;
         /* Report spurious IRQ, once per IRQ line. */
         if (!(spurious_irq_mask & irqmask)) {
-            printk("spurious 8259A interrupt: IRQ%d.\n", irq);
+            printk("cpu%u: spurious 8259A interrupt: IRQ%u\n",
+                   smp_processor_id(), irq);
             spurious_irq_mask |= irqmask;
         }
         /*
@@ -349,7 +350,23 @@ void __init init_IRQ(void)
             continue;
         desc->handler = &i8259A_irq_type;
         per_cpu(vector_irq, cpu)[LEGACY_VECTOR(irq)] = irq;
-        cpumask_copy(desc->arch.cpu_mask, cpumask_of(cpu));
+
+        /*
+         * The interrupt affinity logic never targets interrupts to offline
+         * CPUs, hence it's safe to use cpumask_all here.
+         *
+         * Legacy PIC interrupts are only targeted to CPU0, but depending on
+         * the platform they can be distributed to any online CPU in hardware.
+         * Note this behavior has only been observed on AMD hardware. In order
+         * to cope install all active legacy vectors on all CPUs.
+         *
+         * IO-APIC will change the destination mask if/when taking ownership of
+         * the interrupt.
+         */
+        cpumask_copy(desc->arch.cpu_mask,
+                     (boot_cpu_data.x86_vendor &
+                      (X86_VENDOR_AMD | X86_VENDOR_HYGON) ? &cpumask_all
+                                                          : cpumask_of(cpu)));
         desc->arch.vector = LEGACY_VECTOR(irq);
     }
     
diff --git a/xen/arch/x86/irq.c b/xen/arch/x86/irq.c
index f42ad539dc..16d9fceba1 100644
--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -1920,7 +1920,16 @@ void do_IRQ(struct cpu_user_regs *regs)
                 kind = "";
             if ( !(vector >= FIRST_LEGACY_VECTOR &&
                    vector <= LAST_LEGACY_VECTOR &&
-                   !smp_processor_id() &&
+                   (!smp_processor_id() ||
+                    /*
+                     * For AMD/Hygon do spurious PIC interrupt
+                     * detection on all CPUs, as it has been observed
+                     * that during unknown circumstances spurious PIC
+                     * interrupts have been delivered to CPUs
+                     * different than the BSP.
+                     */
+                    (boot_cpu_data.x86_vendor & (X86_VENDOR_AMD |
+                                                 X86_VENDOR_HYGON))) &&
                    bogus_8259A_irq(vector - FIRST_LEGACY_VECTOR)) )
             {
                 printk("CPU%u: No irq handler for vector %02x (IRQ %d%s)\n",
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.18