On 08/11/2009 04:00 AM, Anthony Liguori wrote:
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.
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@xxxxxxxxxx>
---
arch/x86/kvm/x86.c | 23 +++++++++++++++++------
1 files changed, 17 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 6263991..48b1be9 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4050,6 +4050,16 @@ static void save_state_to_tss32(struct kvm_vcpu *vcpu,
tss->ldt_selector = get_segment_selector(vcpu, VCPU_SREG_LDTR);
}
+static int load_seg_from_tss32(struct kvm_vcpu *vcpu,
+ struct tss_segment_32 *tss,
+ u16 selector, int type_bits, int seg)
+{
+ if ((tss->eflags& X86_EFLAGS_VM))
+ return kvm_load_realmode_segment(vcpu, selector, seg);
+
+ return kvm_load_segment_descriptor(vcpu, selector, type_bits, seg);
+}
+
kvm_load_segment_descriptor() can already load plain segments:
if (!(vcpu->arch.cr0 & X86_CR0_PE))
return kvm_load_realmode_segment(vcpu, selector, seg);
so we can simplify the patch a bit by extending the check.
--
error compiling committee.c: too many arguments to function
--
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