From: David Vrabel <david.vrabel@citrix.com>
If a PCI System Error (SERR) is asserted it causes an NMI. If this NMI
occurs while the CPU is in printk() then Xen may deadlock as
pci_serr_error() calls console_force_unlock() which screws up the
console lock.
printk() isn''t safe to call from NMI context so defer the diagnostic
message to a softirq.
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Tested-by: George Dunlap <george.dunlap@eu.citrix.com>
---
xen/arch/x86/traps.c | 13 ++++++++++---
xen/include/asm-x86/softirq.h | 3 ++-
2 files changed, 12 insertions(+), 4 deletions(-)
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index b6f7b9a..35c17f2 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -3173,6 +3173,11 @@ static void nmi_mce_softirq(void)
st->vcpu = NULL;
}
+static void pci_serr_softirq(void)
+{
+ printk("\n\nNMI - PCI system error (SERR)\n");
+}
+
void async_exception_cleanup(struct vcpu *curr)
{
int trap;
@@ -3259,10 +3264,11 @@ static void nmi_dom0_report(unsigned int reason_idx)
static void pci_serr_error(struct cpu_user_regs *regs)
{
- console_force_unlock();
- printk("\n\nNMI - PCI system error (SERR)\n");
-
outb((inb(0x61) & 0x0f) | 0x04, 0x61); /* clear-and-disable the PCI
SERR error line. */
+
+ /* Would like to print a diagnostic here but can''t call printk()
+ from NMI context -- raise a softirq instead. */
+ raise_softirq(PCI_SERR_SOFTIRQ);
}
static void io_check_error(struct cpu_user_regs *regs)
@@ -3563,6 +3569,7 @@ void __init trap_init(void)
cpu_init();
open_softirq(NMI_MCE_SOFTIRQ, nmi_mce_softirq);
+ open_softirq(PCI_SERR_SOFTIRQ, pci_serr_softirq);
}
long register_guest_nmi_callback(unsigned long address)
diff --git a/xen/include/asm-x86/softirq.h b/xen/include/asm-x86/softirq.h
index 4387803..9d8e2e1 100644
--- a/xen/include/asm-x86/softirq.h
+++ b/xen/include/asm-x86/softirq.h
@@ -6,6 +6,7 @@
#define VCPU_KICK_SOFTIRQ (NR_COMMON_SOFTIRQS + 2)
#define MACHINE_CHECK_SOFTIRQ (NR_COMMON_SOFTIRQS + 3)
-#define NR_ARCH_SOFTIRQS 4
+#define PCI_SERR_SOFTIRQ (NR_COMMON_SOFTIRQS + 4)
+#define NR_ARCH_SOFTIRQS 5
#endif /* __ASM_SOFTIRQ_H__ */
--
1.7.2.5