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Subject[PATCH v2 09/14] KVM: x86: Handle emulation failure directly in kvm_task_switch()
Date
Consolidate the reporting of emulation failure into kvm_task_switch()
so that it can return EMULATE_USER_EXIT. This helps pave the way for
removing EMULATE_FAIL altogether.

This also fixes a theoretical bug where task switch interception could
suppress an EMULATE_USER_EXIT return.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/kvm/svm.c | 11 ++---------
arch/x86/kvm/vmx/vmx.c | 14 +++-----------
arch/x86/kvm/x86.c | 9 ++++++---
3 files changed, 11 insertions(+), 23 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 9c46031e96cc..eab01c5d59f7 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -3892,17 +3892,10 @@ static int task_switch_interception(struct vcpu_svm *svm)
if (int_type != SVM_EXITINTINFO_TYPE_SOFT)
int_vec = -1;

- if (kvm_task_switch(&svm->vcpu, tss_selector, int_vec, reason,
- has_error_code, error_code) == EMULATE_FAIL)
- goto fail;

- return 1;

-fail:
- svm->vcpu.run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
- svm->vcpu.run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
- svm->vcpu.run->internal.ndata = 0;
- return 0;
+ return kvm_task_switch(&svm->vcpu, tss_selector, int_vec, reason,
+ has_error_code, error_code) != EMULATE_USER_EXIT;
}

static int cpuid_interception(struct vcpu_svm *svm)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index c6ba452296e3..a80613a5921f 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5073,21 +5073,13 @@ static int handle_task_switch(struct kvm_vcpu *vcpu)
type != INTR_TYPE_NMI_INTR))
skip_emulated_instruction(vcpu);

- if (kvm_task_switch(vcpu, tss_selector,
- type == INTR_TYPE_SOFT_INTR ? idt_index : -1, reason,
- has_error_code, error_code) == EMULATE_FAIL) {
- vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
- vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
- vcpu->run->internal.ndata = 0;
- return 0;
- }
-
/*
* TODO: What about debug traps on tss switch?
* Are we supposed to inject them and update dr6?
*/
-
- return 1;
+ return kvm_task_switch(vcpu, tss_selector,
+ type == INTR_TYPE_SOFT_INTR ? idt_index : -1,
+ reason, has_error_code, error_code) != EMULATE_USER_EXIT;
}

static int handle_ept_violation(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1a886ec6957d..83b3c7e9fce7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8587,9 +8587,12 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int idt_index,

ret = emulator_task_switch(ctxt, tss_selector, idt_index, reason,
has_error_code, error_code);
-
- if (ret)
- return EMULATE_FAIL;
+ if (ret) {
+ vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+ vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
+ vcpu->run->internal.ndata = 0;
+ return EMULATE_USER_EXIT;
+ }

kvm_rip_write(vcpu, ctxt->eip);
kvm_set_rflags(vcpu, ctxt->eflags);
--
2.22.0
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