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KVM: x86: Exit to userspace if fastpath triggers one on instruction skip

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Exit to userspace if a fastpath handler triggers such an exit, which can
happen when skipping the instruction, e.g. due to userspace
single-stepping the guest via KVM_GUESTDBG_SINGLESTEP or because of an
emulation failure.

Fixes: 404d5d7bff ("KVM: X86: Introduce more exit_fastpath_completion enum values")
Link: https://lore.kernel.org/r/20240802195120.325560-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2024-08-02 12:51:18 -07:00
parent ea60229af7
commit f7f39c50ed
2 changed files with 8 additions and 2 deletions
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1
arch/x86/include/asm/kvm_host.h
View File

@ -211,6 +211,7 @@ enum exit_fastpath_completion {
EXIT_FASTPATH_NONE,
EXIT_FASTPATH_REENTER_GUEST,
EXIT_FASTPATH_EXIT_HANDLED,
EXIT_FASTPATH_EXIT_USERSPACE,
};
typedef enum exit_fastpath_completion fastpath_t;

9
arch/x86/kvm/x86.c
View File

@ -2206,8 +2206,10 @@ fastpath_t handle_fastpath_set_msr_irqoff(struct kvm_vcpu *vcpu)
}
if (handled) {
kvm_skip_emulated_instruction(vcpu);
ret = EXIT_FASTPATH_REENTER_GUEST;
if (!kvm_skip_emulated_instruction(vcpu))
ret = EXIT_FASTPATH_EXIT_USERSPACE;
else
ret = EXIT_FASTPATH_REENTER_GUEST;
trace_kvm_msr_write(msr, data);
} else {
ret = EXIT_FASTPATH_NONE;
@ -11196,6 +11198,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
if (vcpu->arch.apic_attention)
kvm_lapic_sync_from_vapic(vcpu);
if (unlikely(exit_fastpath == EXIT_FASTPATH_EXIT_USERSPACE))
return 0;
r = kvm_x86_call(handle_exit)(vcpu, exit_fastpath);
return r;