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KVM: Fix task switch back link handling. 

Back link is written to a wrong TSS now.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Gleb Natapov 2009-03-30 16:03:24 +03:00 committed by Avi Kivity
parent 8843419048
commit b237ac37a1
1 changed files with 32 additions and 8 deletions
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40
arch/x86/kvm/x86.c
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@ -3717,7 +3717,6 @@ 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);
}
static int load_state_from_tss32(struct kvm_vcpu *vcpu,
@ -3814,8 +3813,8 @@ static int load_state_from_tss16(struct kvm_vcpu *vcpu,
}
static int kvm_task_switch_16(struct kvm_vcpu *vcpu, u16 tss_selector,
u32 old_tss_base,
struct desc_struct *nseg_desc)
u16 old_tss_sel, u32 old_tss_base,
struct desc_struct *nseg_desc)
{
struct tss_segment_16 tss_segment_16;
int ret = 0;
@ -3834,6 +3833,16 @@ static int kvm_task_switch_16(struct kvm_vcpu *vcpu, u16 tss_selector,
&tss_segment_16, sizeof tss_segment_16))
goto out;
if (old_tss_sel != 0xffff) {
tss_segment_16.prev_task_link = old_tss_sel;
if (kvm_write_guest(vcpu->kvm,
get_tss_base_addr(vcpu, nseg_desc),
&tss_segment_16.prev_task_link,
sizeof tss_segment_16.prev_task_link))
goto out;
}
if (load_state_from_tss16(vcpu, &tss_segment_16))
goto out;
@ -3843,7 +3852,7 @@ static int kvm_task_switch_16(struct kvm_vcpu *vcpu, u16 tss_selector,
}
static int kvm_task_switch_32(struct kvm_vcpu *vcpu, u16 tss_selector,
u32 old_tss_base,
u16 old_tss_sel, u32 old_tss_base,
struct desc_struct *nseg_desc)
{
struct tss_segment_32 tss_segment_32;
@ -3863,6 +3872,16 @@ static int kvm_task_switch_32(struct kvm_vcpu *vcpu, u16 tss_selector,
&tss_segment_32, sizeof tss_segment_32))
goto out;
if (old_tss_sel != 0xffff) {
tss_segment_32.prev_task_link = old_tss_sel;
if (kvm_write_guest(vcpu->kvm,
get_tss_base_addr(vcpu, nseg_desc),
&tss_segment_32.prev_task_link,
sizeof tss_segment_32.prev_task_link))
goto out;
}
if (load_state_from_tss32(vcpu, &tss_segment_32))
goto out;
@ -3918,12 +3937,17 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int reason)
kvm_x86_ops->skip_emulated_instruction(vcpu);
/* set back link to prev task only if NT bit is set in eflags
note that old_tss_sel is not used afetr this point */
if (reason != TASK_SWITCH_CALL && reason != TASK_SWITCH_GATE)
old_tss_sel = 0xffff;
if (nseg_desc.type & 8)
ret = kvm_task_switch_32(vcpu, tss_selector, old_tss_base,
&nseg_desc);
ret = kvm_task_switch_32(vcpu, tss_selector, old_tss_sel,
old_tss_base, &nseg_desc);
else
ret = kvm_task_switch_16(vcpu, tss_selector, old_tss_base,
&nseg_desc);
ret = kvm_task_switch_16(vcpu, tss_selector, old_tss_sel,
old_tss_base, &nseg_desc);
if (reason == TASK_SWITCH_CALL || reason == TASK_SWITCH_GATE) {
u32 eflags = kvm_x86_ops->get_rflags(vcpu);