From: Andrew Cooper <andrew.cooper3@citrix.com>
Date: Fri, 22 May 2015 08:13:04 +0000 (+0200)
Subject: x86/irq: limit the maximum number of domain PIRQs
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~3172
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=75d28c917094b0e264874e92e8980b00a372b99f;p=xen.git

x86/irq: limit the maximum number of domain PIRQs

c/s 7e73a6e "have architectures specify the number of PIRQs a hardware domain
gets" increased the default number of pirqs for dom0, as 256 was found to be
too low in some cases.

However, it didn't account for the upper bound presented by the domains EOI
bitmap, registered with the PHYSDEVOP_pirq_eoi_gmfn_v* hypercall.

On a server with 240 cpus, Xen was observed to be attempting to clear the EOI
bit for dom0's pirq 0xb40f, which hit a pagefault.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---

diff --git a/xen/arch/x86/io_apic.c b/xen/arch/x86/io_apic.c
index 976c0c58c5..6f66562b4f 100644
--- a/xen/arch/x86/io_apic.c
+++ b/xen/arch/x86/io_apic.c
@@ -2614,6 +2614,10 @@ unsigned int arch_hwdom_irqs(domid_t domid)
     if ( !domid )
         n = min(n, dom0_max_vcpus());
     n = min(nr_irqs_gsi + n * NR_DYNAMIC_VECTORS, nr_irqs);
+
+    /* Bounded by the domain pirq eoi bitmap gfn. */
+    n = min_t(unsigned int, n, PAGE_SIZE * BITS_PER_BYTE);
+
     printk("Dom%d has maximum %u PIRQs\n", domid, n);
 
     return n;
diff --git a/xen/arch/x86/irq.c b/xen/arch/x86/irq.c
index 1a219174cc..fe1ee333b8 100644
--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -1073,13 +1073,19 @@ bool_t cpu_has_pending_apic_eoi(void)
 static inline void set_pirq_eoi(struct domain *d, unsigned int irq)
 {
     if ( d->arch.pirq_eoi_map )
+    {
+        ASSERT(irq < PAGE_SIZE * BITS_PER_BYTE);
         set_bit(irq, d->arch.pirq_eoi_map);
+    }
 }
 
 static inline void clear_pirq_eoi(struct domain *d, unsigned int irq)
 {
     if ( d->arch.pirq_eoi_map )
+    {
+        ASSERT(irq < PAGE_SIZE * BITS_PER_BYTE);
         clear_bit(irq, d->arch.pirq_eoi_map);
+    }
 }
 
 static void set_eoi_ready(void *data);