From 64c8ca38e22fa858721d89f33a1a3511e0aba1dc Mon Sep 17 00:00:00 2001 From: David Vrabel Date: Thu, 23 Feb 2012 10:31:48 +0000 Subject: [PATCH] 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 Tested-by: George Dunlap Committed-by: Keir Fraser xen-unstable changeset: 24690:dcc6d57e4c07 xen-unstable date: Thu Feb 02 15:28:58 2012 +0000 --- 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 6f8a6ff4de..b8abd3781d 100644 --- a/xen/arch/x86/traps.c +++ b/xen/arch/x86/traps.c @@ -3049,6 +3049,11 @@ 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; @@ -3138,10 +3143,11 @@ 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) @@ -3444,6 +3450,7 @@ 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 4387803910..9d8e2e14ca 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__ */ -- 2.39.5