| Message ID | 20230109130605.2013555-1-eesposit@redhat.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | xapic: make sure x2APIC -> xapic transition correctly | expand |
On Mon, 09 Jan 2023 08:06:03 -0500, Emanuele Giuseppe Esposito wrote: > The root cause is kvm_lapic_set_base() failing to handle x2APIC -> xapic ID > switch, which is addressed by patch 1. > Patch 2 provides a selftest to verify this behavior. > > This serie is an RFC because I think that commit ef40757743b47 already tries to > fix one such effect of the error made in kvm_lapic_set_base, but I am not sure > how such error described in the commit message is triggered, nor how to > reproduce it using a selftest. I don't think one can enable/disable x2APIC using > KVM_SET_LAPIC, and kvm_lapic_set_base() in kvm_apic_set_state() just takes care > of updating apic->base_address, since value == old_value. > The test in patch 2 fails with the fix in ef40757743b47. > > [...] Applied to kvm-x86 apic, with the tweak of only stuffing the APIC_ID if the APIC is enabled. I also heavily reworked the testcase (see feedback on that patch). Thanks! [1/2] KVM: x86: Reinitialize xAPIC ID when userspace forces x2APIC => xAPIC https://github.com/kvm-x86/linux/commit/052c3b99cbc8 [2/2] KVM: selftests: Verify APIC_ID is set when forcing x2APIC=>xAPIC transition https://github.com/kvm-x86/linux/commit/eb9819257631 -- https://github.com/kvm-x86/linux/tree/next https://github.com/kvm-x86/linux/tree/fixes
The root cause is kvm_lapic_set_base() failing to handle x2APIC -> xapic ID switch, which is addressed by patch 1. Patch 2 provides a selftest to verify this behavior. This serie is an RFC because I think that commit ef40757743b47 already tries to fix one such effect of the error made in kvm_lapic_set_base, but I am not sure how such error described in the commit message is triggered, nor how to reproduce it using a selftest. I don't think one can enable/disable x2APIC using KVM_SET_LAPIC, and kvm_lapic_set_base() in kvm_apic_set_state() just takes care of updating apic->base_address, since value == old_value. The test in patch 2 fails with the fix in ef40757743b47. Thank you, Emanuele Emanuele Giuseppe Esposito (2): KVM: x86: update APIC_ID also when disabling x2APIC in kvm_lapic_set_base KVM: selftests: APIC_ID must be correctly updated when disabling x2apic arch/x86/kvm/lapic.c | 8 ++- .../selftests/kvm/x86_64/xapic_state_test.c | 64 +++++++++++++++++++ 2 files changed, 70 insertions(+), 2 deletions(-)