[patch 3/3] KVM: VMX: handle segment limit granularity special case in software

Marcelo Tosatti
2008-07-16T22:18:50Z

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As the comment in the diff mentions, VMX does not accept any bit in
the range 11:0 of ES,CS,FS,GS,SS segment registers limit field to
be zero with the granulity bit set to one.

So clear granularity and adjust the limit accordingly.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Index: kvm/arch/x86/kvm/vmx.c
===================================================================
--- kvm.orig/arch/x86/kvm/vmx.c
+++ kvm/arch/x86/kvm/vmx.c
@@ -1665,6 +1665,22 @@ static void vmx_set_segment(struct kvm_v
return;
}
vmcs_writel(sf->base, var->base);
+
+ /*
+ * section 22.3.1.2:
+ * - If any bit in the limit field in the range 11:0 is 0, G must be 0.
+ * - If any bit in the limit field in the range 31:20 is 1, G must be 1.
+ */
+ if (!vcpu->arch.rmode.active && !var->unusable &&
+ seg != VCPU_SREG_TR && seg != VCPU_SREG_LDTR) {
+#define SEG_MASK ((1 << 12)-1)
+ if (var->g && (var->limit & SEG_MASK) != SEG_MASK) {
+ var->g = 0;
+ var->limit <<= 12;
+ var->limit |= SEG_MASK;
+ }
+ }
+
vmcs_write32(sf->limit, var->limit);
vmcs_write16(sf->selector, var->selector);
if (vcpu->arch.rmode.active && var->s) {

--