NSN's proprietary OS DMX sometimes does task switches.
To get it running in KVM the following changes were necessary:
Interrupt injection only with interrupt flag set.
Linking the tss->prev_task_link to itself removed.
Task linking is required for CALL and GATE.
Do not call skip_emulated_instruction() for GATE.
Signed-off-by: Bernhard Kohl <bernhard.kohl@xxxxxxx>
---
arch/x86/kvm/vmx.c | 3 ++-
arch/x86/kvm/x86.c | 19 +++++++++++++++++--
2 files changed, 19 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 5cf28df..eca57a3 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3357,7 +3357,8 @@ static void vmx_intr_assist(struct kvm_vcpu *vcpu)
enable_irq_window(vcpu);
}
if (vcpu->arch.interrupt.pending) {
- vmx_inject_irq(vcpu, vcpu->arch.interrupt.nr);
+ if (vcpu->arch.interrupt_window_open)
+ vmx_inject_irq(vcpu, vcpu->arch.interrupt.nr);
if (kvm_cpu_has_interrupt(vcpu))
enable_irq_window(vcpu);
}
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b556b6a..9052058 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3683,7 +3683,7 @@ static void save_state_to_tss32(struct kvm_vcpu *vcpu,
tss->fs = get_segment_selector(vcpu, VCPU_SREG_FS);
tss->gs = get_segment_selector(vcpu, VCPU_SREG_GS);
tss->ldt_selector = get_segment_selector(vcpu, VCPU_SREG_LDTR);
- tss->prev_task_link = get_segment_selector(vcpu, VCPU_SREG_TR);
+ tss->prev_task_link = 0;
}
static int load_state_from_tss32(struct kvm_vcpu *vcpu,
@@ -3810,6 +3810,7 @@ out:
static int kvm_task_switch_32(struct kvm_vcpu *vcpu, u16 tss_selector,
u32 old_tss_base,
+ u16 old_tss_selector, int reason,
struct desc_struct *nseg_desc)
{
struct tss_segment_32 tss_segment_32;
@@ -3829,6 +3830,18 @@ static int kvm_task_switch_32(struct kvm_vcpu *vcpu, u16
tss_selector,
&tss_segment_32, sizeof tss_segment_32))
goto out;
+ /*
+ * SDM 3: table 6-2
+ * Task linking required for CALL and GATE.
+ */
+ if (reason == TASK_SWITCH_CALL || reason == TASK_SWITCH_GATE)
+ {
+ tss_segment_32.prev_task_link = old_tss_selector;
+ kvm_write_guest(vcpu->kvm, get_tss_base_addr(vcpu, nseg_desc),
+ &tss_segment_32, sizeof(struct tss_segment_32));
+
+ }
+
if (load_state_from_tss32(vcpu, &tss_segment_32))
goto out;
@@ -3882,10 +3895,12 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16
tss_selector, int reason)
kvm_x86_ops->set_rflags(vcpu, eflags & ~X86_EFLAGS_NT);
}
- kvm_x86_ops->skip_emulated_instruction(vcpu);
+ if (reason != TASK_SWITCH_GATE)
+ kvm_x86_ops->skip_emulated_instruction(vcpu);
if (nseg_desc.type & 8)
ret = kvm_task_switch_32(vcpu, tss_selector, old_tss_base,
+ old_tss_sel, reason,
&nseg_desc);
else
ret = kvm_task_switch_16(vcpu, tss_selector, old_tss_base,
--
1.6.0.6
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