xcp-1.6-updates/xen-4.1.hg

changeset 23227:4cb8d9c9d46b

x86: avoid deadlock after a PCI SERR NMI

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>
Committed-by: Keir Fraser <keir@xen.org>
xen-unstable changeset: 24690:dcc6d57e4c07
xen-unstable date: Thu Feb 02 15:28:58 2012 +0000
author David Vrabel <david.vrabel@citrix.com>
date Thu Feb 23 10:31:48 2012 +0000 (2012-02-23)
parents 3b9b0d4003a3
children 0b0d74c97010
files xen/arch/x86/traps.c xen/include/asm-x86/softirq.h
line diff
     1.1 --- a/xen/arch/x86/traps.c	Thu Feb 23 10:30:50 2012 +0000
     1.2 +++ b/xen/arch/x86/traps.c	Thu Feb 23 10:31:48 2012 +0000
     1.3 @@ -3049,6 +3049,11 @@ static void nmi_mce_softirq(void)
     1.4      st->vcpu = NULL;
     1.5  }
     1.6  
     1.7 +static void pci_serr_softirq(void)
     1.8 +{
     1.9 +    printk("\n\nNMI - PCI system error (SERR)\n");
    1.10 +}
    1.11 +
    1.12  void async_exception_cleanup(struct vcpu *curr)
    1.13  {
    1.14      int trap;
    1.15 @@ -3138,10 +3143,11 @@ static void nmi_dom0_report(unsigned int
    1.16  
    1.17  static void pci_serr_error(struct cpu_user_regs *regs)
    1.18  {
    1.19 -    console_force_unlock();
    1.20 -    printk("\n\nNMI - PCI system error (SERR)\n");
    1.21 -
    1.22      outb((inb(0x61) & 0x0f) | 0x04, 0x61); /* clear-and-disable the PCI SERR error line. */
    1.23 +
    1.24 +    /* Would like to print a diagnostic here but can't call printk()
    1.25 +       from NMI context -- raise a softirq instead. */
    1.26 +    raise_softirq(PCI_SERR_SOFTIRQ);
    1.27  }
    1.28  
    1.29  static void io_check_error(struct cpu_user_regs *regs)
    1.30 @@ -3444,6 +3450,7 @@ void __init trap_init(void)
    1.31      cpu_init();
    1.32  
    1.33      open_softirq(NMI_MCE_SOFTIRQ, nmi_mce_softirq);
    1.34 +    open_softirq(PCI_SERR_SOFTIRQ, pci_serr_softirq);
    1.35  }
    1.36  
    1.37  long register_guest_nmi_callback(unsigned long address)
     2.1 --- a/xen/include/asm-x86/softirq.h	Thu Feb 23 10:30:50 2012 +0000
     2.2 +++ b/xen/include/asm-x86/softirq.h	Thu Feb 23 10:31:48 2012 +0000
     2.3 @@ -6,6 +6,7 @@
     2.4  #define VCPU_KICK_SOFTIRQ      (NR_COMMON_SOFTIRQS + 2)
     2.5  
     2.6  #define MACHINE_CHECK_SOFTIRQ  (NR_COMMON_SOFTIRQS + 3)
     2.7 -#define NR_ARCH_SOFTIRQS       4
     2.8 +#define PCI_SERR_SOFTIRQ       (NR_COMMON_SOFTIRQS + 4)
     2.9 +#define NR_ARCH_SOFTIRQS       5
    2.10  
    2.11  #endif /* __ASM_SOFTIRQ_H__ */