[Xen-changelog] [xen master] x86/irq: limit the maximum number of domain PIRQs

[patchbot@xxxxxxx]

commit 75d28c917094b0e264874e92e8980b00a372b99f
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Fri May 22 10:13:04 2015 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri May 22 10:13:04 2015 +0200

    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@xxxxxxxxxx>
---
 xen/arch/x86/io_apic.c |    4 ++++
 xen/arch/x86/irq.c     |    6 ++++++
 2 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/xen/arch/x86/io_apic.c b/xen/arch/x86/io_apic.c
index 976c0c5..6f66562 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 1a21917..fe1ee33 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);
--
generated by git-patchbot for /home/xen/git/xen.git#master

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