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Merge branch 'kvm-svm-harden' into HEAD
This fixes three issues in nested SVM: 1) in the shutdown_interception() vmexit handler we call kvm_vcpu_reset(). However, if running nested and L1 doesn't intercept shutdown, the function resets vcpu->arch.hflags without properly leaving the nested state. This leaves the vCPU in inconsistent state and later triggers a kernel panic in SVM code. The same bug can likely be triggered by sending INIT via local apic to a vCPU which runs a nested guest. On VMX we are lucky that the issue can't happen because VMX always intercepts triple faults, thus triple fault in L2 will always be redirected to L1. Plus, handle_triple_fault() doesn't reset the vCPU. INIT IPI can't happen on VMX either because INIT events are masked while in VMX mode. Secondarily, KVM doesn't honour SHUTDOWN intercept bit of L1 on SVM. A normal hypervisor should always intercept SHUTDOWN, a unit test on the other hand might want to not do so. Finally, the guest can trigger a kernel non rate limited printk on SVM from the guest, which is fixed as well. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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67
tools/testing/selftests/kvm/x86_64/svm_nested_shutdown_test.c
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,67 @@ | ||
| // SPDX-License-Identifier: GPL-2.0-only | ||
| /* | ||
| * svm_nested_shutdown_test | ||
| * | ||
| * Copyright (C) 2022, Red Hat, Inc. | ||
| * | ||
| * Nested SVM testing: test that unintercepted shutdown in L2 doesn't crash the host | ||
| */ | ||
|
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| #include "test_util.h" | ||
| #include "kvm_util.h" | ||
| #include "processor.h" | ||
| #include "svm_util.h" | ||
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| static void l2_guest_code(struct svm_test_data *svm) | ||
| { | ||
| __asm__ __volatile__("ud2"); | ||
| } | ||
|
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| static void l1_guest_code(struct svm_test_data *svm, struct idt_entry *idt) | ||
| { | ||
| #define L2_GUEST_STACK_SIZE 64 | ||
| unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE]; | ||
| struct vmcb *vmcb = svm->vmcb; | ||
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| generic_svm_setup(svm, l2_guest_code, | ||
| &l2_guest_stack[L2_GUEST_STACK_SIZE]); | ||
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| vmcb->control.intercept &= ~(BIT(INTERCEPT_SHUTDOWN)); | ||
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| idt[6].p = 0; // #UD is intercepted but its injection will cause #NP | ||
| idt[11].p = 0; // #NP is not intercepted and will cause another | ||
| // #NP that will be converted to #DF | ||
| idt[8].p = 0; // #DF will cause #NP which will cause SHUTDOWN | ||
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| run_guest(vmcb, svm->vmcb_gpa); | ||
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| /* should not reach here */ | ||
| GUEST_ASSERT(0); | ||
| } | ||
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| int main(int argc, char *argv[]) | ||
| { | ||
| struct kvm_vcpu *vcpu; | ||
| struct kvm_run *run; | ||
| vm_vaddr_t svm_gva; | ||
| struct kvm_vm *vm; | ||
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| TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_SVM)); | ||
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| vm = vm_create_with_one_vcpu(&vcpu, l1_guest_code); | ||
| vm_init_descriptor_tables(vm); | ||
| vcpu_init_descriptor_tables(vcpu); | ||
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| vcpu_alloc_svm(vm, &svm_gva); | ||
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| vcpu_args_set(vcpu, 2, svm_gva, vm->idt); | ||
| run = vcpu->run; | ||
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| vcpu_run(vcpu); | ||
| TEST_ASSERT(run->exit_reason == KVM_EXIT_SHUTDOWN, | ||
| "Got exit_reason other than KVM_EXIT_SHUTDOWN: %u (%s)\n", | ||
| run->exit_reason, | ||
| exit_reason_str(run->exit_reason)); | ||
|
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| kvm_vm_free(vm); | ||
| } |
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