From: Suresh Siddha Date: Thu, 25 Aug 2011 19:01:11 +0000 (-0700) Subject: x86, kdump, ioapic: Reset remote-IRR in clear_IO_APIC X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=1e75b31d638d5242ca8e9771dfdcbd28a5f041df;p=linux-beck.git x86, kdump, ioapic: Reset remote-IRR in clear_IO_APIC In the kdump scenario mentioned below, we can have a case where the device using level triggered interrupt will not generate any interrupts in the kdump kernel. 1. IO-APIC sends a level triggered interrupt to the CPU's local APIC. 2. Kernel crashed before the CPU services this interrupt, leaving the remote-IRR in the IO-APIC set. 3. kdump kernel boot sequence does clear_IO_APIC() as part of IO-APIC initialization. But this fails to reset remote-IRR bit of the IO-APIC RTE as the remote-IRR bit is read-only. 4. Device using that level triggered entry can't generate any more interrupts because of the remote-IRR bit. In clear_IO_APIC_pin(), check if the remote-IRR bit is set and if so do an explicit attempt to clear it (by doing EOI write on modern io-apic's and changing trigger mode to edge/level on older io-apic's). Also before doing the explicit EOI to the io-apic, ensure that the trigger mode is indeed set to level. This will enable the explicit EOI to the io-apic to reset the remote-IRR bit. Tested-by: Leonardo Chiquitto Signed-off-by: Suresh Siddha Fixes: https://bugzilla.novell.com/show_bug.cgi?id=701686 Cc: Rafael Wysocki Cc: Maciej W. Rozycki Cc: Thomas Renninger Cc: jbeulich@novell.com Cc: yinghai@kernel.org Link: http://lkml.kernel.org/r/20110825190657.157502602@sbsiddha-desk.sc.intel.com Signed-off-by: Ingo Molnar --- diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c index 620da6fed6b7..913d4bd2913a 100644 --- a/arch/x86/kernel/apic/io_apic.c +++ b/arch/x86/kernel/apic/io_apic.c @@ -593,10 +593,56 @@ static void clear_IO_APIC_pin(unsigned int apic, unsigned int pin) entry = ioapic_read_entry(apic, pin); if (entry.delivery_mode == dest_SMI) return; + + /* + * Make sure the entry is masked and re-read the contents to check + * if it is a level triggered pin and if the remote-IRR is set. + */ + if (!entry.mask) { + entry.mask = 1; + ioapic_write_entry(apic, pin, entry); + entry = ioapic_read_entry(apic, pin); + } + + if (entry.irr) { + /* + * Make sure the trigger mode is set to level. Explicit EOI + * doesn't clear the remote-IRR if the trigger mode is not + * set to level. + */ + if (!entry.trigger) { + entry.trigger = IOAPIC_LEVEL; + ioapic_write_entry(apic, pin, entry); + } + + if (mpc_ioapic_ver(apic) >= 0x20) { + unsigned long flags; + + raw_spin_lock_irqsave(&ioapic_lock, flags); + io_apic_eoi(apic, entry.vector); + raw_spin_unlock_irqrestore(&ioapic_lock, flags); + } else { + /* + * Mechanism by which we clear remote-IRR in this + * case is by changing the trigger mode to edge and + * back to level. + */ + entry.trigger = IOAPIC_EDGE; + ioapic_write_entry(apic, pin, entry); + entry.trigger = IOAPIC_LEVEL; + ioapic_write_entry(apic, pin, entry); + } + } + /* - * Disable it in the IO-APIC irq-routing table: + * Clear the rest of the bits in the IO-APIC RTE except for the mask + * bit. */ ioapic_mask_entry(apic, pin); + entry = ioapic_read_entry(apic, pin); + if (entry.irr) + printk(KERN_ERR "Unable to reset IRR for apic: %d, pin :%d\n", + mpc_ioapic_id(apic), pin); } static void clear_IO_APIC (void)