Messages in this thread | | | From | Andrew Cooper <> | Subject | Re: [PATCH] x86/xen: Add support for HVMOP_set_evtchn_upcall_vector | Date | Fri, 15 Jul 2022 09:50:11 +0000 |
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On 15/07/2022 09:18, Jane Malalane wrote: > On 14/07/2022 00:27, Boris Ostrovsky wrote: >>> xen_hvm_smp_init(); >>> WARN_ON(xen_cpuhp_setup(xen_cpu_up_prepare_hvm, xen_cpu_dead_hvm)); >>> diff --git a/arch/x86/xen/suspend_hvm.c b/arch/x86/xen/suspend_hvm.c >>> index 9d548b0c772f..be66e027ef28 100644 >>> --- a/arch/x86/xen/suspend_hvm.c >>> +++ b/arch/x86/xen/suspend_hvm.c >>> @@ -5,6 +5,7 @@ >>> #include <xen/hvm.h> >>> #include <xen/features.h> >>> #include <xen/interface/features.h> >>> +#include <xen/events.h> >>> #include "xen-ops.h" >>> @@ -14,6 +15,23 @@ void xen_hvm_post_suspend(int suspend_cancelled) >>> xen_hvm_init_shared_info(); >>> xen_vcpu_restore(); >>> } >>> - xen_setup_callback_vector(); >>> + if (xen_ack_upcall) { >>> + unsigned int cpu; >>> + >>> + for_each_online_cpu(cpu) { >>> + xen_hvm_evtchn_upcall_vector_t op = { >>> + .vector = HYPERVISOR_CALLBACK_VECTOR, >>> + .vcpu = per_cpu(xen_vcpu_id, cpu), >>> + }; >>> + >>> + BUG_ON(HYPERVISOR_hvm_op(HVMOP_set_evtchn_upcall_vector, >>> + &op)); >>> + /* Trick toolstack to think we are enlightened. */ >>> + if (!cpu) >>> + BUG_ON(xen_set_callback_via(1)); >> >> What are you trying to make the toolstack aware of? That we have *a* >> callback (either global or percpu)? > Yes, specifically for the check in libxl__domain_pvcontrol_available.
And others.
This is all a giant bodge, but basically a lot of tooling uses the non-zero-ness of the CALLBACK_VIA param to determine whether the VM has Xen-aware drivers loaded or not.
The value 1 is a CALLBACK_VIA value which encodes GSI 1, and the only reason this doesn't explode everywhere is because the evtchn_upcall_vector registration takes priority over GSI delivery.
This is decades of tech debt piled on top of tech debt.
~Andrew
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