Non-x86 folks, there's nothing interesting to see here, y'all got pulled in because removing KVM_REQ_UNHALT requires deleting kvm_clear_request() from arch code. Note, this based on: https://github.com/sean-jc/linux.git tags/kvm-x86-6.1-1 to pre-resolve conflicts with the event/exception cleanups in there. In Paolo's words... The following backtrace: [ 1355.807187] kvm_vcpu_map+0x159/0x190 [kvm] [ 1355.807628] nested_svm_vmexit+0x4c/0x7f0 [kvm_amd] [ 1355.808036] ? kvm_vcpu_block+0x54/0xa0 [kvm] [ 1355.808450] svm_check_nested_events+0x97/0x390 [kvm_amd] [ 1355.808920] kvm_check_nested_events+0x1c/0x40 [kvm] [ 1355.809396] kvm_arch_vcpu_runnable+0x4e/0x190 [kvm] [ 1355.809892] kvm_vcpu_check_block+0x4f/0x100 [kvm] [ 1355.811259] kvm_vcpu_block+0x6b/0xa0 [kvm] can occur due to kmap being called in non-sleepable (!TASK_RUNNING) context. The fix is to extend kvm_x86_ops->nested_ops.hv_timer_pending() to cover all events not already checked in kvm_arch_vcpu_is_runnable(), and then get rid of the annoying (and wrong) call to kvm_check_nested_events() from kvm_vcpu_check_block(). Beware, this is not a complete fix, because kvm_guest_apic_has_interrupt() might still _read_ memory from non-sleepable context. The fix here is probably to make kvm_arch_vcpu_is_runnable() return -EAGAIN, and in that case do a round of kvm_vcpu_check_block() polling in sleepable context. Nevertheless, it is a good start as it pushes the vmexit into vcpu_block(). The series also does a small cleanup pass on kvm_vcpu_check_block(), removing KVM_REQ_UNHALT in favor of simply calling kvm_arch_vcpu_runnable() again. Now that kvm_check_nested_events() is not called anymore by kvm_arch_vcpu_runnable(), it is much easier to see that KVM will never consume the event that caused kvm_vcpu_has_events() to return true, and therefore it is safe to evaluate it again. The alternative of propagating the return value of kvm_arch_vcpu_runnable() up to kvm_vcpu_{block,halt}() is inferior because it does not quite get right the edge cases where the vCPU becomes runnable right before schedule() or right after kvm_vcpu_check_block(). While these edge cases are unlikely to truly matter in practice, it is also pointless to get them "wrong". v4: - Make event request if INIT/SIPI is pending when GIF=>1 (SVM) and on nested VM-Enter (VMX). - Make an event request at VMXOFF iff it's necessary. - Keep the INIT/SIPI pending vs. blocked checks separate (for the above nSVM/nVMX fixes). - Check the result of kvm_check_nested_events() in vcpu_block(). - Rename INIT/SIPI helpers (hopefully we'll eventually rename all of the related collateral, e.g. "pending_events" is so misleading). - Drop pending INIT/SIPI snaphsot to avoid creating weird, conflicting code when kvm_check_nested_events() is called by vcpu_block(). v3: - https://lore.kernel.org/all/20220822170659.2527086-1-pbonzini@xxxxxxxxxx - do not propagate the return value of kvm_arch_vcpu_runnable() up to kvm_vcpu_{block,halt}() - move and reformat the comment in vcpu_block() move KVM_REQ_UNHALT removal last Paolo Bonzini (5): KVM: x86: make vendor code check for all nested events KVM: x86: lapic does not have to process INIT if it is blocked KVM: x86: never write to memory from kvm_vcpu_check_block() KVM: mips, x86: do not rely on KVM_REQ_UNHALT KVM: remove KVM_REQ_UNHALT Sean Christopherson (7): KVM: nVMX: Make an event request when pending an MTF nested VM-Exit KVM: x86: Rename and expose helper to detect if INIT/SIPI are allowed KVM: x86: Rename kvm_apic_has_events() to make it INIT/SIPI specific KVM: SVM: Make an event request if INIT or SIPI is pending when GIF is set KVM: nVMX: Make an event request if INIT or SIPI is pending on VM-Enter KVM: nVMX: Make event request on VMXOFF iff INIT/SIPI is pending KVM: x86: Don't snapshot pending INIT/SIPI prior to checking nested events Documentation/virt/kvm/vcpu-requests.rst | 28 +-------------- arch/arm64/kvm/arm.c | 1 - arch/mips/kvm/emulate.c | 6 ++-- arch/powerpc/kvm/book3s_pr.c | 1 - arch/powerpc/kvm/book3s_pr_papr.c | 1 - arch/powerpc/kvm/booke.c | 1 - arch/powerpc/kvm/powerpc.c | 1 - arch/riscv/kvm/vcpu_insn.c | 1 - arch/s390/kvm/kvm-s390.c | 2 -- arch/x86/include/asm/kvm_host.h | 2 +- arch/x86/kvm/lapic.c | 38 ++++++-------------- arch/x86/kvm/lapic.h | 9 ++++- arch/x86/kvm/svm/svm.c | 3 +- arch/x86/kvm/vmx/nested.c | 33 +++++++++-------- arch/x86/kvm/vmx/vmx.c | 6 ++-- arch/x86/kvm/x86.c | 46 +++++++++++++++--------- arch/x86/kvm/x86.h | 5 --- arch/x86/kvm/xen.c | 1 - include/linux/kvm_host.h | 3 +- virt/kvm/kvm_main.c | 4 +-- 20 files changed, 79 insertions(+), 113 deletions(-) base-commit: 5df50a4a9b60afba4dd2be76d0f0fb8ae8c9beab -- 2.37.3.968.ga6b4b080e4-goog _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
