[PATCH] KVM: x86: Add instruction length to VCPU event state

[Jan Kiszka]

From: Jan Kiszka <jan.kis...@siemens.com>

VMX requires a properly set instruction length VM entry field when
trying to inject soft exception and interrupts. We have to preserve this
state across VM save/restore to avoid breaking the re-injection of such
events on Intel. So add it to the new VCPU event state.

Signed-off-by: Jan Kiszka <jan.kis...@siemens.com>
---

Existing qemu[-kvm]-0.12 that is already prepared for 2.6.33 will need
an update now. Whenever we actually ran into the case that
event_exit_inst_len was evaluated by VMX, we were playing roulette with
a high probability to crash the guest. This will not changes for already
released 0.12.x versions.

 Documentation/kvm/api.txt  |    2 ++
 arch/x86/include/asm/kvm.h |    3 ++-
 arch/x86/kvm/x86.c         |    4 ++++
 3 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/Documentation/kvm/api.txt b/Documentation/kvm/api.txt
index c6416a3..aa11d70 100644
--- a/Documentation/kvm/api.txt
+++ b/Documentation/kvm/api.txt
@@ -686,6 +686,8 @@ struct kvm_vcpu_events {
        } nmi;
        __u32 sipi_vector;
        __u32 flags;
+       __u32 instruction_length; /* used by VMX */
+       __u32 reserved[9];
 };
 
 4.30 KVM_SET_VCPU_EVENTS
diff --git a/arch/x86/include/asm/kvm.h b/arch/x86/include/asm/kvm.h
index f46b79f..570b6cc 100644
--- a/arch/x86/include/asm/kvm.h
+++ b/arch/x86/include/asm/kvm.h
@@ -281,7 +281,8 @@ struct kvm_vcpu_events {
        } nmi;
        __u32 sipi_vector;
        __u32 flags;
-       __u32 reserved[10];
+       __u32 instruction_length; /* used by VMX */
+       __u32 reserved[9];
 };
 
 #endif /* _ASM_X86_KVM_H */
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 86b739f..0cc6cfb 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2134,6 +2134,8 @@ static void kvm_vcpu_ioctl_x86_get_vcpu_events(struct 
kvm_vcpu *vcpu,
        events->nmi.pending = vcpu->arch.nmi_pending;
        events->nmi.masked = kvm_x86_ops->get_nmi_mask(vcpu);
 
+       events->instruction_length = vcpu->arch.event_exit_inst_len;
+
        events->sipi_vector = vcpu->arch.sipi_vector;
 
        events->flags = (KVM_VCPUEVENT_VALID_NMI_PENDING
@@ -2170,6 +2172,8 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct 
kvm_vcpu *vcpu,
        if (events->flags & KVM_VCPUEVENT_VALID_SIPI_VECTOR)
                vcpu->arch.sipi_vector = events->sipi_vector;
 
+       vcpu->arch.event_exit_inst_len = events->instruction_length;
+
        vcpu_put(vcpu);
 
        return 0;

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