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| author | Felipe Franciosi <felipe@nutanix.com> | 2020-05-19 08:11:22 +0000 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2020-06-11 12:35:18 -0400 |
| commit | 384dea1c9183880be183cfaae161d99aafd16df6 (patch) | |
| tree | 9f6acf93b84ce4a5867bc3c08f69507583b0549d | |
| parent | 7e464770a434f7e29bad4b2da7894d32775d6d6f (diff) | |
| download | lwn-384dea1c9183880be183cfaae161d99aafd16df6.tar.gz lwn-384dea1c9183880be183cfaae161d99aafd16df6.zip | |
KVM: x86: respect singlestep when emulating instruction
When userspace configures KVM_GUESTDBG_SINGLESTEP, KVM will manage the
presence of X86_EFLAGS_TF via kvm_set/get_rflags on vcpus. The actual
rflag bit is therefore hidden from callers.
That includes init_emulate_ctxt() which uses the value returned from
kvm_get_flags() to set ctxt->tf. As a result, x86_emulate_instruction()
will skip a single step, leaving singlestep_rip stale and not returning
to userspace.
This resolves the issue by observing the vcpu guest_debug configuration
alongside ctxt->tf in x86_emulate_instruction(), performing the single
step if set.
Cc: stable@vger.kernel.org
Signed-off-by: Felipe Franciosi <felipe@nutanix.com>
Message-Id: <20200519081048.8204-1-felipe@nutanix.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
| -rw-r--r-- | arch/x86/kvm/x86.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 87ee76b73d72..172843a8c314 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -7010,7 +7010,7 @@ restart: if (!ctxt->have_exception || exception_type(ctxt->exception.vector) == EXCPT_TRAP) { kvm_rip_write(vcpu, ctxt->eip); - if (r && ctxt->tf) + if (r && (ctxt->tf || (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP))) r = kvm_vcpu_do_singlestep(vcpu); if (kvm_x86_ops.update_emulated_instruction) kvm_x86_ops.update_emulated_instruction(vcpu); |