From e179f6914152eca9b338e7d8445684062f560c55 Mon Sep 17 00:00:00 2001 From: "K. Y. Srinivasan" Date: Mon, 14 Apr 2014 11:43:49 -0700 Subject: [PATCH 1/2] x86, irq, pic: Probe for legacy PIC and set legacy_pic appropriately The legacy PIC may or may not be available and we need a mechanism to detect the existence of the legacy PIC that is applicable for all hardware (both physical as well as virtual) currently supported by Linux. On Hyper-V, when our legacy firmware presented to the guests, emulates the legacy PIC while when our EFI based firmware is presented we do not emulate the PIC. To support Hyper-V EFI firmware, we had to set the legacy_pic to the null_legacy_pic since we had to bypass PIC based calibration in the early boot code. While, on the EFI firmware, we know we don't emulate the legacy PIC, we need a generic mechanism to detect the presence of the legacy PIC that is not based on boot time state - this became apparent when we tried to get kexec to work on Hyper-V EFI firmware. This patch implements the proposal put forth by H. Peter Anvin : Write a known value to the PIC data port and read it back. If the value read is the value written, we do have the PIC, if not there is no PIC and we can safely set the legacy_pic to null_legacy_pic. Since the read from an unconnected I/O port returns 0xff, we will use ~(1 << PIC_CASCADE_IR) (0xfb: mask all lines except the cascade line) to probe for the existence of the PIC. In version V1 of the patch, I had cleaned up the code based on comments from Peter. In version V2 of the patch, I have addressed additional comments from Peter. In version V3 of the patch, I have addressed Jan's comments (JBeulich@suse.com). In version V4 of the patch, I have addressed additional comments from Peter. Signed-off-by: K. Y. Srinivasan Link: http://lkml.kernel.org/r/1397501029-29286-1-git-send-email-kys@microsoft.com Cc: Thomas Gleixner Signed-off-by: H. Peter Anvin --- arch/x86/kernel/cpu/mshyperv.c | 9 --------- arch/x86/kernel/i8259.c | 20 +++++++++++++++++++- 2 files changed, 19 insertions(+), 10 deletions(-) diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index 76f98fe5b35c..a450373e8e91 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -132,15 +132,6 @@ static void __init ms_hyperv_init_platform(void) lapic_timer_frequency = hv_lapic_frequency; printk(KERN_INFO "HyperV: LAPIC Timer Frequency: %#x\n", lapic_timer_frequency); - - /* - * On Hyper-V, when we are booting off an EFI firmware stack, - * we do not have many legacy devices including PIC, PIT etc. - */ - if (efi_enabled(EFI_BOOT)) { - printk(KERN_INFO "HyperV: Using null_legacy_pic\n"); - legacy_pic = &null_legacy_pic; - } } #endif diff --git a/arch/x86/kernel/i8259.c b/arch/x86/kernel/i8259.c index 2e977b5d61dd..8af817105e29 100644 --- a/arch/x86/kernel/i8259.c +++ b/arch/x86/kernel/i8259.c @@ -299,13 +299,31 @@ static void unmask_8259A(void) static void init_8259A(int auto_eoi) { unsigned long flags; + unsigned char probe_val = ~(1 << PIC_CASCADE_IR); + unsigned char new_val; i8259A_auto_eoi = auto_eoi; raw_spin_lock_irqsave(&i8259A_lock, flags); - outb(0xff, PIC_MASTER_IMR); /* mask all of 8259A-1 */ + /* + * Check to see if we have a PIC. + * Mask all except the cascade and read + * back the value we just wrote. If we don't + * have a PIC, we will read 0xff as opposed to the + * value we wrote. + */ outb(0xff, PIC_SLAVE_IMR); /* mask all of 8259A-2 */ + outb(probe_val, PIC_MASTER_IMR); + new_val = inb(PIC_MASTER_IMR); + if (new_val != probe_val) { + printk(KERN_INFO "Using NULL legacy PIC\n"); + legacy_pic = &null_legacy_pic; + raw_spin_unlock_irqrestore(&i8259A_lock, flags); + return; + } + + outb(0xff, PIC_MASTER_IMR); /* mask all of 8259A-1 */ /* * outb_pic - this has to work on a wide range of PC hardware. From fb24da805729ee4a83efa34015948f7d64da4b28 Mon Sep 17 00:00:00 2001 From: Prarit Bhargava Date: Wed, 2 Apr 2014 08:11:13 -0400 Subject: [PATCH 2/2] x86/irq: Fix fixup_irqs() error handling Several patches to fix cpu hotplug and the down'd cpu's irq relocations have been submitted in the past month or so. The patches should resolve the problems with cpu hotplug and irq relocation, however, there is always a possibility that a bug still exists. The big problem with debugging these irq reassignments is that the cpu down completes and then we get random stack traces from drivers for which irqs have not been properly assigned to a new cpu. The stack traces are a mix of storage, network, and other kernel subsystem (I once saw the serial port stop working ...) warnings and failures. The problem with these failures is that they are difficult to diagnose. There is no warning in the cpu hotplug down path to indicate that an IRQ has failed to be assigned to a new cpu, and all we are left with is a stack trace from a driver, or a non-functional device. If we had some information on the console debugging these situations would be much easier; after all we can map an IRQ to a device by simply using lspci or /proc/interrupts. The current code, fixup_irqs(), which migrates IRQs from the down'd cpu and is called close to the end of the cpu down path, calls chip->set_irq_affinity which eventually calls __assign_irq_vector(). Errors are not propogated back from this function call and this results in silent irq relocation failures. This patch fixes this issue by returning the error codes up the call stack and prints out a warning if there is a relocation failure. Signed-off-by: Prarit Bhargava Acked-by: Thomas Gleixner Cc: Rui Wang Cc: Liu Ping Fan Cc: Bjorn Helgaas Cc: Yoshihiro YUNOMAE Cc: Lv Zheng Cc: Seiji Aguchi Cc: Yang Zhang Cc: Andi Kleen Cc: Steven Rostedt (Red Hat) Cc: Li Fei Cc: gong.chen@linux.intel.com Link: http://lkml.kernel.org/r/1396440673-18286-1-git-send-email-prarit@redhat.com [ Made small cleanliness tweaks. ] Signed-off-by: Ingo Molnar --- arch/x86/kernel/apic/io_apic.c | 28 ++++++++++++++++++---------- arch/x86/kernel/irq.c | 13 +++++++++---- 2 files changed, 27 insertions(+), 14 deletions(-) diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c index 6ad4658de705..b4b21db9f4ad 100644 --- a/arch/x86/kernel/apic/io_apic.c +++ b/arch/x86/kernel/apic/io_apic.c @@ -2312,7 +2312,7 @@ int __ioapic_set_affinity(struct irq_data *data, const struct cpumask *mask, int err; if (!config_enabled(CONFIG_SMP)) - return -1; + return -EPERM; if (!cpumask_intersects(mask, cpu_online_mask)) return -EINVAL; @@ -2343,7 +2343,7 @@ int native_ioapic_set_affinity(struct irq_data *data, int ret; if (!config_enabled(CONFIG_SMP)) - return -1; + return -EPERM; raw_spin_lock_irqsave(&ioapic_lock, flags); ret = __ioapic_set_affinity(data, mask, &dest); @@ -3075,9 +3075,11 @@ msi_set_affinity(struct irq_data *data, const struct cpumask *mask, bool force) struct irq_cfg *cfg = data->chip_data; struct msi_msg msg; unsigned int dest; + int ret; - if (__ioapic_set_affinity(data, mask, &dest)) - return -1; + ret = __ioapic_set_affinity(data, mask, &dest); + if (ret) + return ret; __get_cached_msi_msg(data->msi_desc, &msg); @@ -3177,9 +3179,11 @@ dmar_msi_set_affinity(struct irq_data *data, const struct cpumask *mask, struct irq_cfg *cfg = data->chip_data; unsigned int dest, irq = data->irq; struct msi_msg msg; + int ret; - if (__ioapic_set_affinity(data, mask, &dest)) - return -1; + ret = __ioapic_set_affinity(data, mask, &dest); + if (ret) + return ret; dmar_msi_read(irq, &msg); @@ -3226,9 +3230,11 @@ static int hpet_msi_set_affinity(struct irq_data *data, struct irq_cfg *cfg = data->chip_data; struct msi_msg msg; unsigned int dest; + int ret; - if (__ioapic_set_affinity(data, mask, &dest)) - return -1; + ret = __ioapic_set_affinity(data, mask, &dest); + if (ret) + return ret; hpet_msi_read(data->handler_data, &msg); @@ -3295,9 +3301,11 @@ ht_set_affinity(struct irq_data *data, const struct cpumask *mask, bool force) { struct irq_cfg *cfg = data->chip_data; unsigned int dest; + int ret; - if (__ioapic_set_affinity(data, mask, &dest)) - return -1; + ret = __ioapic_set_affinity(data, mask, &dest); + if (ret) + return ret; target_ht_irq(data->irq, dest, cfg->vector); return IRQ_SET_MASK_OK_NOCOPY; diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c index 283a76a9cc40..49bbb57da7f5 100644 --- a/arch/x86/kernel/irq.c +++ b/arch/x86/kernel/irq.c @@ -357,6 +357,7 @@ void fixup_irqs(void) struct irq_desc *desc; struct irq_data *data; struct irq_chip *chip; + int ret; for_each_irq_desc(irq, desc) { int break_affinity = 0; @@ -395,10 +396,14 @@ void fixup_irqs(void) if (!irqd_can_move_in_process_context(data) && chip->irq_mask) chip->irq_mask(data); - if (chip->irq_set_affinity) - chip->irq_set_affinity(data, affinity, true); - else if (!(warned++)) - set_affinity = 0; + if (chip->irq_set_affinity) { + ret = chip->irq_set_affinity(data, affinity, true); + if (ret == -ENOSPC) + pr_crit("IRQ %d set affinity failed because there are no available vectors. The device assigned to this IRQ is unstable.\n", irq); + } else { + if (!(warned++)) + set_affinity = 0; + } /* * We unmask if the irq was not marked masked by the