Hi Kai, On 4/14/23 6:34 AM, Huang, Kai wrote: > On Wed, 2023-04-12 at 20:41 -0700, Kuppuswamy Sathyanarayanan wrote: >> Host-guest event notification via configured interrupt vector is useful >> in cases where a guest makes an asynchronous request and needs a >> callback from the host to indicate the completion or to let the host >> notify the guest about events like device removal. One usage example is, >> callback requirement of GetQuote asynchronous hypercall. >> >> In TDX guest, SetupEventNotifyInterrupt hypercall can be used by the >> guest to specify which interrupt vector to use as an event-notify >> vector from the VMM. Details about the SetupEventNotifyInterrupt >> hypercall can be found in TDX Guest-Host Communication Interface >> (GHCI) Specification, section "VP.VMCALL<SetupEventNotifyInterrupt>". >> >> As per design, VMM will post the event completion IRQ using the same >> CPU on which SetupEventNotifyInterrupt hypercall request is received. >> So allocate an IRQ vector from "x86_vector_domain", and set the CPU >> affinity of the IRQ vector to the CPU on which >> SetupEventNotifyInterrupt hypercall is made. >> >> Add tdx_register_event_irq_cb()/tdx_unregister_event_irq_cb() >> interfaces to allow drivers register/unregister event noficiation > ^ > to register/unregister >> handlers. >> >> > > [...] > With suggested changes, the final version looks like below. +/** + * tdx_event_irq_init() - Register IRQ for event notification from the VMM to + * the TDX Guest. + * + * Use SetupEventNotifyInterrupt TDVMCALL to register the event notification + * IRQ with the VMM, which is used by the VMM to notify the TDX guest when + * needed, for instance, when VMM finishes the GetQuote request from the TDX + * guest. The VMM always notifies the TDX guest via the same CPU on which the + * SetupEventNotifyInterrupt TDVMCALL is called. For simplicity, just allocate + * an IRQ (and a vector) directly from x86_vector_domain for such notification + * and pin the IRQ to the same CPU on which TDVMCALL is called. + * + * Since tdx_event_irq_init() is triggered via early_initcall(), it will be + * called before secondary CPUs bring up, so no special logic is required to + * ensure that the same CPU is used for SetupEventNotifyInterrupt TDVMCALL and + * IRQ allocation. + */ +static int __init tdx_event_irq_init(void) +{ + struct irq_affinity_desc desc; + struct irq_alloc_info info; + struct irq_cfg *cfg; + int irq; + + if (!cpu_feature_enabled(X86_FEATURE_TDX_GUEST)) + return 0; + + init_irq_alloc_info(&info, NULL); + + cpumask_set_cpu(smp_processor_id(), &desc.mask); + + irq = __irq_domain_alloc_irqs(x86_vector_domain, -1, 1, cpu_to_node(0), + &info, false, &desc); + if (irq <= 0) { + pr_err("Event notification IRQ allocation failed %d\n", irq); + return -EIO; + } + + irq_set_handler(irq, handle_edge_irq); + + /* + * The IRQ cannot be migrated because VMM always notifies the TDX + * guest on the same CPU on which the SetupEventNotifyInterrupt + * TDVMCALL is called. Set the IRQ with IRQF_NOBALANCING to prevent + * its affinity from being changed. + */ + if (request_irq(irq, tdx_event_irq_handler, IRQF_NOBALANCING, + "tdx_event_irq", NULL)) { + pr_err("Event notification IRQ request failed\n"); + goto err_free_domain_irqs; + } + + cfg = irq_cfg(irq); + + if (_tdx_hypercall(TDVMCALL_SETUP_NOTIFY_INTR, cfg->vector, 0, 0, 0)) { + pr_err("Event notification hypercall failed\n"); + goto err_free_irqs; + } + + tdx_event_irq = irq; + + return 0; + +err_free_irqs: + free_irq(irq, NULL); +err_free_domain_irqs: + irq_domain_free_irqs(irq, 1); + + return -EIO; +} +early_initcall(tdx_event_irq_init) -- Sathyanarayanan Kuppuswamy Linux Kernel Developer