From 72a9b186292d98494f222226cfd24a1621796209 Mon Sep 17 00:00:00 2001 From: KarimAllah Ahmed Date: Fri, 26 Aug 2016 23:55:36 +0200 Subject: [PATCH] xen: Remove event channel notification through Xen PCI platform device Ever since commit 254d1a3f02eb ("xen/pv-on-hvm kexec: shutdown watches from old kernel") using the INTx interrupt from Xen PCI platform device for event channel notification would just lockup the guest during bootup. postcore_initcall now calls xs_reset_watches which will eventually try to read a value from XenStore and will get stuck on read_reply at XenBus forever since the platform driver is not probed yet and its INTx interrupt handler is not registered yet. That means that the guest can not be notified at this moment of any pending event channels and none of the per-event handlers will ever be invoked (including the XenStore one) and the reply will never be picked up by the kernel. The exact stack where things get stuck during xenbus_init: -xenbus_init -xs_init -xs_reset_watches -xenbus_scanf -xenbus_read -xs_single -xs_single -xs_talkv Vector callbacks have always been the favourite event notification mechanism since their introduction in commit 38e20b07efd5 ("x86/xen: event channels delivery on HVM.") and the vector callback feature has always been advertised for quite some time by Xen that's why INTx was broken for several years now without impacting anyone. Luckily this also means that event channel notification through INTx is basically dead-code which can be safely removed without impacting anybody since it has been effectively disabled for more than 4 years with nobody complaining about it (at least as far as I'm aware of). This commit removes event channel notification through Xen PCI platform device. Cc: Boris Ostrovsky Cc: David Vrabel Cc: Juergen Gross Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: x86@kernel.org Cc: Konrad Rzeszutek Wilk Cc: Bjorn Helgaas Cc: Stefano Stabellini Cc: Julien Grall Cc: Vitaly Kuznetsov Cc: Paul Gortmaker Cc: Ross Lagerwall Cc: xen-devel@lists.xenproject.org Cc: linux-kernel@vger.kernel.org Cc: linux-pci@vger.kernel.org Cc: Anthony Liguori Signed-off-by: KarimAllah Ahmed Reviewed-by: Boris Ostrovsky Signed-off-by: David Vrabel --- arch/x86/include/asm/xen/events.h | 11 ------ arch/x86/pci/xen.c | 2 +- arch/x86/xen/enlighten.c | 21 +++------- arch/x86/xen/smp.c | 2 - arch/x86/xen/time.c | 5 --- drivers/xen/events/events_base.c | 26 +++++-------- drivers/xen/platform-pci.c | 64 ------------------------------- include/xen/xen.h | 3 +- 8 files changed, 17 insertions(+), 117 deletions(-) diff --git a/arch/x86/include/asm/xen/events.h b/arch/x86/include/asm/xen/events.h index e6911caf5bbf..608a79d5a466 100644 --- a/arch/x86/include/asm/xen/events.h +++ b/arch/x86/include/asm/xen/events.h @@ -20,15 +20,4 @@ static inline int xen_irqs_disabled(struct pt_regs *regs) /* No need for a barrier -- XCHG is a barrier on x86. */ #define xchg_xen_ulong(ptr, val) xchg((ptr), (val)) -extern int xen_have_vector_callback; - -/* - * Events delivered via platform PCI interrupts are always - * routed to vcpu 0 and hence cannot be rebound. - */ -static inline bool xen_support_evtchn_rebind(void) -{ - return (!xen_hvm_domain() || xen_have_vector_callback); -} - #endif /* _ASM_X86_XEN_EVENTS_H */ diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c index 3a483cb5ac81..bedfab98077a 100644 --- a/arch/x86/pci/xen.c +++ b/arch/x86/pci/xen.c @@ -456,7 +456,7 @@ void __init xen_msi_init(void) int __init pci_xen_hvm_init(void) { - if (!xen_have_vector_callback || !xen_feature(XENFEAT_hvm_pirqs)) + if (!xen_feature(XENFEAT_hvm_pirqs)) return 0; #ifdef CONFIG_ACPI diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index a9ba14ac3aea..366b6aed4a8e 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -137,8 +137,6 @@ struct shared_info xen_dummy_shared_info; void *xen_initial_gdt; RESERVE_BRK(shared_info_page_brk, PAGE_SIZE); -__read_mostly int xen_have_vector_callback; -EXPORT_SYMBOL_GPL(xen_have_vector_callback); static int xen_cpu_up_prepare(unsigned int cpu); static int xen_cpu_up_online(unsigned int cpu); @@ -1524,10 +1522,7 @@ static void __init xen_pvh_early_guest_init(void) if (!xen_feature(XENFEAT_auto_translated_physmap)) return; - if (!xen_feature(XENFEAT_hvm_callback_vector)) - return; - - xen_have_vector_callback = 1; + BUG_ON(!xen_feature(XENFEAT_hvm_callback_vector)); xen_pvh_early_cpu_init(0, false); xen_pvh_set_cr_flags(0); @@ -1864,9 +1859,7 @@ static int xen_cpu_up_prepare(unsigned int cpu) xen_vcpu_setup(cpu); } - if (xen_pv_domain() || - (xen_have_vector_callback && - xen_feature(XENFEAT_hvm_safe_pvclock))) + if (xen_pv_domain() || xen_feature(XENFEAT_hvm_safe_pvclock)) xen_setup_timer(cpu); rc = xen_smp_intr_init(cpu); @@ -1882,9 +1875,7 @@ static int xen_cpu_dead(unsigned int cpu) { xen_smp_intr_free(cpu); - if (xen_pv_domain() || - (xen_have_vector_callback && - xen_feature(XENFEAT_hvm_safe_pvclock))) + if (xen_pv_domain() || xen_feature(XENFEAT_hvm_safe_pvclock)) xen_teardown_timer(cpu); return 0; @@ -1922,8 +1913,8 @@ static void __init xen_hvm_guest_init(void) xen_panic_handler_init(); - if (xen_feature(XENFEAT_hvm_callback_vector)) - xen_have_vector_callback = 1; + BUG_ON(!xen_feature(XENFEAT_hvm_callback_vector)); + xen_hvm_smp_init(); WARN_ON(xen_cpuhp_setup()); xen_unplug_emulated_devices(); @@ -1961,7 +1952,7 @@ bool xen_hvm_need_lapic(void) return false; if (!xen_hvm_domain()) return false; - if (xen_feature(XENFEAT_hvm_pirqs) && xen_have_vector_callback) + if (xen_feature(XENFEAT_hvm_pirqs)) return false; return true; } diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c index 137afbbd0590..311acad7dad2 100644 --- a/arch/x86/xen/smp.c +++ b/arch/x86/xen/smp.c @@ -765,8 +765,6 @@ static void __init xen_hvm_smp_prepare_cpus(unsigned int max_cpus) void __init xen_hvm_smp_init(void) { - if (!xen_have_vector_callback) - return; smp_ops.smp_prepare_cpus = xen_hvm_smp_prepare_cpus; smp_ops.smp_send_reschedule = xen_smp_send_reschedule; smp_ops.cpu_die = xen_cpu_die; diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c index 67356d29d74d..33d8f6a7829d 100644 --- a/arch/x86/xen/time.c +++ b/arch/x86/xen/time.c @@ -432,11 +432,6 @@ static void xen_hvm_setup_cpu_clockevents(void) void __init xen_hvm_init_time_ops(void) { - /* vector callback is needed otherwise we cannot receive interrupts - * on cpu > 0 and at this point we don't know how many cpus are - * available */ - if (!xen_have_vector_callback) - return; if (!xen_feature(XENFEAT_hvm_safe_pvclock)) { printk(KERN_INFO "Xen doesn't support pvclock on HVM," "disable pv timer\n"); diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c index d5dbdb9d24d8..9ecfcdcdd6d6 100644 --- a/drivers/xen/events/events_base.c +++ b/drivers/xen/events/events_base.c @@ -1314,9 +1314,6 @@ static int rebind_irq_to_cpu(unsigned irq, unsigned tcpu) if (!VALID_EVTCHN(evtchn)) return -1; - if (!xen_support_evtchn_rebind()) - return -1; - /* Send future instances of this interrupt to other vcpu. */ bind_vcpu.port = evtchn; bind_vcpu.vcpu = xen_vcpu_nr(tcpu); @@ -1650,20 +1647,15 @@ void xen_callback_vector(void) { int rc; uint64_t callback_via; - if (xen_have_vector_callback) { - callback_via = HVM_CALLBACK_VECTOR(HYPERVISOR_CALLBACK_VECTOR); - rc = xen_set_callback_via(callback_via); - if (rc) { - pr_err("Request for Xen HVM callback vector failed\n"); - xen_have_vector_callback = 0; - return; - } - pr_info("Xen HVM callback vector for event delivery is enabled\n"); - /* in the restore case the vector has already been allocated */ - if (!test_bit(HYPERVISOR_CALLBACK_VECTOR, used_vectors)) - alloc_intr_gate(HYPERVISOR_CALLBACK_VECTOR, - xen_hvm_callback_vector); - } + + callback_via = HVM_CALLBACK_VECTOR(HYPERVISOR_CALLBACK_VECTOR); + rc = xen_set_callback_via(callback_via); + BUG_ON(rc); + pr_info("Xen HVM callback vector for event delivery is enabled\n"); + /* in the restore case the vector has already been allocated */ + if (!test_bit(HYPERVISOR_CALLBACK_VECTOR, used_vectors)) + alloc_intr_gate(HYPERVISOR_CALLBACK_VECTOR, + xen_hvm_callback_vector); } #else void xen_callback_vector(void) {} diff --git a/drivers/xen/platform-pci.c b/drivers/xen/platform-pci.c index cf9666680c8c..b59c9455aae1 100644 --- a/drivers/xen/platform-pci.c +++ b/drivers/xen/platform-pci.c @@ -42,7 +42,6 @@ static unsigned long platform_mmio; static unsigned long platform_mmio_alloc; static unsigned long platform_mmiolen; -static uint64_t callback_via; static unsigned long alloc_xen_mmio(unsigned long len) { @@ -55,51 +54,6 @@ static unsigned long alloc_xen_mmio(unsigned long len) return addr; } -static uint64_t get_callback_via(struct pci_dev *pdev) -{ - u8 pin; - int irq; - - irq = pdev->irq; - if (irq < 16) - return irq; /* ISA IRQ */ - - pin = pdev->pin; - - /* We don't know the GSI. Specify the PCI INTx line instead. */ - return ((uint64_t)0x01 << 56) | /* PCI INTx identifier */ - ((uint64_t)pci_domain_nr(pdev->bus) << 32) | - ((uint64_t)pdev->bus->number << 16) | - ((uint64_t)(pdev->devfn & 0xff) << 8) | - ((uint64_t)(pin - 1) & 3); -} - -static irqreturn_t do_hvm_evtchn_intr(int irq, void *dev_id) -{ - xen_hvm_evtchn_do_upcall(); - return IRQ_HANDLED; -} - -static int xen_allocate_irq(struct pci_dev *pdev) -{ - return request_irq(pdev->irq, do_hvm_evtchn_intr, - IRQF_NOBALANCING | IRQF_TRIGGER_RISING, - "xen-platform-pci", pdev); -} - -static int platform_pci_resume(struct pci_dev *pdev) -{ - int err; - if (xen_have_vector_callback) - return 0; - err = xen_set_callback_via(callback_via); - if (err) { - dev_err(&pdev->dev, "platform_pci_resume failure!\n"); - return err; - } - return 0; -} - static int platform_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent) { @@ -138,21 +92,6 @@ static int platform_pci_probe(struct pci_dev *pdev, platform_mmio = mmio_addr; platform_mmiolen = mmio_len; - if (!xen_have_vector_callback) { - ret = xen_allocate_irq(pdev); - if (ret) { - dev_warn(&pdev->dev, "request_irq failed err=%d\n", ret); - goto out; - } - callback_via = get_callback_via(pdev); - ret = xen_set_callback_via(callback_via); - if (ret) { - dev_warn(&pdev->dev, "Unable to set the evtchn callback " - "err=%d\n", ret); - goto out; - } - } - max_nr_gframes = gnttab_max_grant_frames(); grant_frames = alloc_xen_mmio(PAGE_SIZE * max_nr_gframes); ret = gnttab_setup_auto_xlat_frames(grant_frames); @@ -184,9 +123,6 @@ static struct pci_driver platform_driver = { .name = DRV_NAME, .probe = platform_pci_probe, .id_table = platform_pci_tbl, -#ifdef CONFIG_PM - .resume_early = platform_pci_resume, -#endif }; static int __init platform_pci_init(void) diff --git a/include/xen/xen.h b/include/xen/xen.h index 0c0e3ef4c45d..f0f0252cff9a 100644 --- a/include/xen/xen.h +++ b/include/xen/xen.h @@ -38,8 +38,7 @@ extern enum xen_domain_type xen_domain_type; */ #include #define xen_pvh_domain() (xen_pv_domain() && \ - xen_feature(XENFEAT_auto_translated_physmap) && \ - xen_have_vector_callback) + xen_feature(XENFEAT_auto_translated_physmap)) #else #define xen_pvh_domain() (0) #endif -- 2.20.1