[PATCH 21/42] KVM: VMX: Enhance invalid guest state emulation

Avi Kivity
2009-11-16T12:20:52Z

From: Mohammed Gamal <m.gamal005@gmail.com>

- Change returned handle_invalid_guest_state() to return relevant exit codes
- Move triggering the emulation from vmx_vcpu_run() to vmx_handle_exit()
- Return to userspace instead of repeatedly trying to emulate instructions that have already failed

Signed-off-by: Mohammed Gamal <m.gamal005@gmail.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
---
arch/x86/kvm/vmx.c | 44 ++++++++++++++++++++------------------------
1 files changed, 20 insertions(+), 24 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 4635298..73cb5dd 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -107,7 +107,6 @@ struct vcpu_vmx {
} rmode;
int vpid;
bool emulation_required;
- enum emulation_result invalid_state_emulation_result;

/* Support for vnmi-less CPUs */
int soft_vnmi_blocked;
@@ -3322,35 +3321,37 @@ static int handle_nmi_window(struct kvm_vcpu *vcpu)
return 1;
}

-static void handle_invalid_guest_state(struct kvm_vcpu *vcpu)
+static int handle_invalid_guest_state(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
enum emulation_result err = EMULATE_DONE;
-
- local_irq_enable();
- preempt_enable();
+ int ret = 1;

while (!guest_state_valid(vcpu)) {
err = emulate_instruction(vcpu, 0, 0, 0);

- if (err == EMULATE_DO_MMIO)
- break;
+ if (err == EMULATE_DO_MMIO) {
+ ret = 0;
+ goto out;
+ }

if (err != EMULATE_DONE) {
kvm_report_emulation_failure(vcpu, "emulation failure");
- break;
+ vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+ vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
+ ret = 0;
+ goto out;
}

if (signal_pending(current))
- break;
+ goto out;
if (need_resched())
schedule();
}

- preempt_disable();
- local_irq_disable();
-
- vmx->invalid_state_emulation_result = err;
+ vmx->emulation_required = 0;
+out:
+ return ret;
}

/*
@@ -3406,13 +3407,9 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu)

trace_kvm_exit(exit_reason, kvm_rip_read(vcpu));

- /* If we need to emulate an MMIO from handle_invalid_guest_state
- * we just return 0 */
- if (vmx->emulation_required && emulate_invalid_guest_state) {
- if (guest_state_valid(vcpu))
- vmx->emulation_required = 0;
- return vmx->invalid_state_emulation_result != EMULATE_DO_MMIO;
- }
+ /* If guest state is invalid, start emulating */
+ if (vmx->emulation_required && emulate_invalid_guest_state)
+ return handle_invalid_guest_state(vcpu);

/* Access CR3 don't cause VMExit in paging mode, so we need
* to sync with guest real CR3. */
@@ -3607,11 +3604,10 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
if (unlikely(!cpu_has_virtual_nmis() && vmx->soft_vnmi_blocked))
vmx->entry_time = ktime_get();

- /* Handle invalid guest state instead of entering VMX */
- if (vmx->emulation_required && emulate_invalid_guest_state) {
- handle_invalid_guest_state(vcpu);
+ /* Don't enter VMX if guest state is invalid, let the exit handler
+ start emulation until we arrive back to a valid state */
+ if (vmx->emulation_required && emulate_invalid_guest_state)
return;
- }

if (test_bit(VCPU_REGS_RSP, (unsigned long *)&vcpu->arch.regs_dirty))
vmcs_writel(GUEST_RSP, vcpu->arch.regs[VCPU_REGS_RSP]);
--
1.6.5.2