diff options
| author | Anthony Liguori <aliguori@us.ibm.com> | 2009-08-11 15:57:59 -0500 |
|---|---|---|
| committer | Avi Kivity <avi@redhat.com> | 2009-09-10 10:46:44 +0300 |
| commit | c0c7c04b874bf98a10d8e0c8322a5d3bc93536bc (patch) | |
| tree | fd1fd86a26767fb8b59db3190f17b2c40a035ba4 | |
| parent | 345dcaa8fde7fa70252d58c862bf41fd2149ca2c (diff) | |
KVM: When switching to a vm8086 task, load segments as 16-bit
According to 16.2.5 in the SDM, eflags.vm in the tss is consulted before loading
and new segments. If eflags.vm == 1, then the segments are treated as 16-bit
segments. The LDTR and TR are not normally available in vm86 mode so if they
happen to somehow get loaded, they need to be treated as 32-bit segments.
This fixes an invalid vmentry failure in a custom OS that was happening after
a task switch into vm8086 mode. Since the segments were being mistakenly
treated as 32-bit, we loaded garbage state.
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
| -rw-r--r-- | arch/x86/kvm/x86.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 31bf98427f4e..1aa7e6d91d4f 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4101,12 +4101,19 @@ static int kvm_load_realmode_segment(struct kvm_vcpu *vcpu, u16 selector, int se return 0; } +static int is_vm86_segment(struct kvm_vcpu *vcpu, int seg) +{ + return (seg != VCPU_SREG_LDTR) && + (seg != VCPU_SREG_TR) && + (kvm_x86_ops->get_rflags(vcpu) & X86_EFLAGS_VM); +} + int kvm_load_segment_descriptor(struct kvm_vcpu *vcpu, u16 selector, int type_bits, int seg) { struct kvm_segment kvm_seg; - if (!(vcpu->arch.cr0 & X86_CR0_PE)) + if (is_vm86_segment(vcpu, seg) || !(vcpu->arch.cr0 & X86_CR0_PE)) return kvm_load_realmode_segment(vcpu, selector, seg); if (load_segment_descriptor_to_kvm_desct(vcpu, selector, &kvm_seg)) return 1; |