| Message ID | 20240719235107.3023592-1-seanjc@google.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | KVM: x86: Fix ICR handling when x2AVIC is active | expand |
On Fri, 19 Jul 2024 16:50:57 -0700, Sean Christopherson wrote: > I made the mistake of expanding my testing to run with and without AVIC > enabled, and to my surprise (wow, sarcasm), x2AVIC failed hard on the > xapic_state_test due to ICR issues. > > AFAICT, the issue is that AMD splits the 64-bit ICR into the legacy ICR > and ICR2 fields when storing the ICR in the vAPIC (apparently "it's a > single 64-bit register" is open to intepretation). Aside from causing > the selftest failure and potential live migration issues, botching the > format is quite bad, as KVM will mishandle incomplete virtualized IPIs, > e.g. generate IRQs to the wrong vCPU, drop IRQs, etc. > > [...] Applied to kvm-x86 misc, thanks! [01/10] KVM: x86: Enforce x2APIC's must-be-zero reserved ICR bits https://github.com/kvm-x86/linux/commit/71bf395a276f [02/10] KVM: x86: Move x2APIC ICR helper above kvm_apic_write_nodecode() https://github.com/kvm-x86/linux/commit/d33234342f8b [03/10] KVM: x86: Re-split x2APIC ICR into ICR+ICR2 for AMD (x2AVIC) https://github.com/kvm-x86/linux/commit/73b42dc69be8 [04/10] KVM: selftests: Open code vcpu_run() equivalent in guest_printf test https://github.com/kvm-x86/linux/commit/d1c2cdca5a08 [05/10] KVM: selftests: Report unhandled exceptions on x86 as regular guest asserts https://github.com/kvm-x86/linux/commit/ed24ba6c2c34 [06/10] KVM: selftests: Add x86 helpers to play nice with x2APIC MSR #GPs https://github.com/kvm-x86/linux/commit/f2e91e874179 [07/10] KVM: selftests: Skip ICR.BUSY test in xapic_state_test if x2APIC is enabled https://github.com/kvm-x86/linux/commit/faf06a238254 [08/10] KVM: selftests: Test x2APIC ICR reserved bits https://github.com/kvm-x86/linux/commit/3426cb48adb4 [09/10] KVM: selftests: Verify the guest can read back the x2APIC ICR it wrote https://github.com/kvm-x86/linux/commit/0cb26ec32085 [10/10] KVM: selftests: Play nice with AMD's AVIC errata https://github.com/kvm-x86/linux/commit/5a7c7d148e48 -- https://github.com/kvm-x86/linux/tree/next
I made the mistake of expanding my testing to run with and without AVIC enabled, and to my surprise (wow, sarcasm), x2AVIC failed hard on the xapic_state_test due to ICR issues. AFAICT, the issue is that AMD splits the 64-bit ICR into the legacy ICR and ICR2 fields when storing the ICR in the vAPIC (apparently "it's a single 64-bit register" is open to intepretation). Aside from causing the selftest failure and potential live migration issues, botching the format is quite bad, as KVM will mishandle incomplete virtualized IPIs, e.g. generate IRQs to the wrong vCPU, drop IRQs, etc. Patch 1 fixes are rather annoying wart where the xapic_state *deliberately* skips reserved bit tests to work around a KVM bug. *sigh* I couldn't find anything definitive in the APM, my findings are based on testing on Genoa. v2: Actually send the whole series. Sean Christopherson (10): KVM: x86: Enforce x2APIC's must-be-zero reserved ICR bits KVM: x86: Move x2APIC ICR helper above kvm_apic_write_nodecode() KVM: x86: Re-split x2APIC ICR into ICR+ICR2 for AMD (x2AVIC) KVM: selftests: Open code vcpu_run() equivalent in guest_printf test KVM: selftests: Report unhandled exceptions on x86 as regular guest asserts KVM: selftests: Add x86 helpers to play nice with x2APIC MSR #GPs KVM: selftests: Skip ICR.BUSY test in xapic_state_test if x2APIC is enabled KVM: selftests: Test x2APIC ICR reserved bits KVM: selftests: Verify the guest can read back the x2APIC ICR it wrote KVM: selftests: Play nice with AMD's AVIC errata arch/x86/include/asm/kvm_host.h | 2 + arch/x86/kvm/lapic.c | 73 +++++++++++++------ arch/x86/kvm/svm/svm.c | 2 + arch/x86/kvm/vmx/main.c | 2 + .../testing/selftests/kvm/guest_print_test.c | 19 ++++- .../selftests/kvm/include/x86_64/apic.h | 21 +++++- .../selftests/kvm/lib/x86_64/processor.c | 8 +- .../selftests/kvm/x86_64/xapic_state_test.c | 54 +++++++++----- 8 files changed, 135 insertions(+), 46 deletions(-) base-commit: 332d2c1d713e232e163386c35a3ba0c1b90df83f