On Tue, Aug 26, 2025 at 4:31 PM Sean Christopherson seanjc@google.com wrote:
On Tue, Aug 26, 2025, Sagi Shahar wrote:
On Tue, Aug 26, 2025 at 3:29 PM Sagi Shahar sagis@google.com wrote:
On Tue, Aug 26, 2025 at 3:14 PM Ira Weiny ira.weiny@intel.com wrote:
Sean Christopherson wrote:
Ugh. IMO, this is a KVM bug. Allowing KVM_CREATE_IRQCHIP for a TDX VM is simply wrong. It _can't_ work. Waiting until KVM_CREATE_VCPU to fail setup is terrible ABI.
If we stretch the meaning of ENOTTY a bit and return that when trying to create a fully in-kernel IRQCHIP for a TDX VM, then the selftests code Just Works thanks to the code below, which handles the scenario where KVM was be built without
^^^^^^^^^^I'm not following. Was there supposed to be a patch attached?
I think Sean refers to the original implementation which was out of the scope for the git diff so it was left out of the patch:
Yep, exactly.
I took a stab at updating the KVM ABI and sent out a small patch [1] to fail KVM_CREATE_IRQCHIP with ENOTTY and the test passes without the special handling for SPLIT_IRQCHIP for TDX.
[1] https://lore.kernel.org/lkml/20250826213455.2338722-1-sagis@google.com/
/*
- Allocate a fully in-kernel IRQ chip by default, but fall back to a
- split model (x86 only) if that fails (KVM x86 allows compiling out
- support for KVM_CREATE_IRQCHIP).
*/ r = __vm_ioctl(vm, KVM_CREATE_IRQCHIP, NULL); if (r && errno == ENOTTY && kvm_has_cap(KVM_CAP_SPLIT_IRQCHIP)) vm_enable_cap(vm, KVM_CAP_SPLIT_IRQCHIP, 24); else TEST_ASSERT_VM_VCPU_IOCTL(!r, KVM_CREATE_IRQCHIP, r, vm);