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KVM: fix CPU reset wrt HF2_GIF_MASK
HF2_GIF_MASK is set in env->hflags2 unconditionally on CPU reset
(see x86_cpu_reset()) but when calling KVM_SET_NESTED_STATE,
KVM_STATE_NESTED_GIF_SET is only valid for nSVM as e.g. nVMX code
looks like

if (kvm_state->hdr.vmx.vmxon_pa == -1ull) {
    if (kvm_state->flags & ~KVM_STATE_NESTED_EVMCS)
        return -EINVAL;
}

Also, when adjusting the environment after KVM_GET_NESTED_STATE we
need not reset HF2_GIF_MASK on VMX as e.g. x86_cpu_pending_interrupt()
expects it to be set.

Alternatively, we could've made env->hflags2 SVM-only.

Reported-by: Jan Kiszka <jan.kiszka@siemens.com>
Fixes: b16c0e2 ("KVM: add support for AMD nested live migration")
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20200723142701.2521161-1-vkuznets@redhat.com>
Tested-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
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vittyvk authored and ehabkost committed Jul 23, 2020
1 parent 8ffa52c commit 0baa4b4
Showing 1 changed file with 11 additions and 5 deletions.
16 changes: 11 additions & 5 deletions target/i386/kvm.c
Expand Up @@ -3877,7 +3877,9 @@ static int kvm_put_nested_state(X86CPU *cpu)
} else {
env->nested_state->flags &= ~KVM_STATE_NESTED_GUEST_MODE;
}
if (env->hflags2 & HF2_GIF_MASK) {

/* Don't set KVM_STATE_NESTED_GIF_SET on VMX as it is illegal */
if (cpu_has_svm(env) && (env->hflags2 & HF2_GIF_MASK)) {
env->nested_state->flags |= KVM_STATE_NESTED_GIF_SET;
} else {
env->nested_state->flags &= ~KVM_STATE_NESTED_GIF_SET;
Expand Down Expand Up @@ -3919,10 +3921,14 @@ static int kvm_get_nested_state(X86CPU *cpu)
} else {
env->hflags &= ~HF_GUEST_MASK;
}
if (env->nested_state->flags & KVM_STATE_NESTED_GIF_SET) {
env->hflags2 |= HF2_GIF_MASK;
} else {
env->hflags2 &= ~HF2_GIF_MASK;

/* Keep HF2_GIF_MASK set on !SVM as x86_cpu_pending_interrupt() needs it */
if (cpu_has_svm(env)) {
if (env->nested_state->flags & KVM_STATE_NESTED_GIF_SET) {
env->hflags2 |= HF2_GIF_MASK;
} else {
env->hflags2 &= ~HF2_GIF_MASK;
}
}

return ret;
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