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KVM: nVMX: Allow setting the VMXE bit in CR4

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This patch allows the guest to enable the VMXE bit in CR4, which is a
prerequisite to running VMXON.

Whether to allow setting the VMXE bit now depends on the architecture (svm
or vmx), so its checking has moved to kvm_x86_ops->set_cr4(). This function
now returns an int: If kvm_x86_ops->set_cr4() returns 1, __kvm_set_cr4()
will also return 1, and this will cause kvm_set_cr4() will throw a #GP.

Turning on the VMXE bit is allowed only when the nested VMX feature is
enabled, and turning it off is forbidden after a vmxon.

Signed-off-by: Nadav Har'El <nyh@il.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Nadav Har'El
2011-05-25 23:03:24 +03:00
committed by Avi Kivity
parent ec378aeef9
commit 5e1746d620
4 changed files with 22 additions and 7 deletions
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17
arch/x86/kvm/vmx.c
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@@ -2121,7 +2121,7 @@ static void ept_save_pdptrs(struct kvm_vcpu *vcpu)
(unsigned long *)&vcpu->arch.regs_dirty);
}
static void vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4);
static int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4);
static void ept_update_paging_mode_cr0(unsigned long *hw_cr0,
unsigned long cr0,
@@ -2219,11 +2219,23 @@ static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
vmcs_writel(GUEST_CR3, guest_cr3);
}
static void vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
static int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
{
unsigned long hw_cr4 = cr4 | (to_vmx(vcpu)->rmode.vm86_active ?
KVM_RMODE_VM_CR4_ALWAYS_ON : KVM_PMODE_VM_CR4_ALWAYS_ON);
if (cr4 & X86_CR4_VMXE) {
/*
* To use VMXON (and later other VMX instructions), a guest
* must first be able to turn on cr4.VMXE (see handle_vmon()).
* So basically the check on whether to allow nested VMX
* is here.
*/
if (!nested_vmx_allowed(vcpu))
return 1;
} else if (to_vmx(vcpu)->nested.vmxon)
return 1;
vcpu->arch.cr4 = cr4;
if (enable_ept) {
if (!is_paging(vcpu)) {
@@ -2236,6 +2248,7 @@ static void vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
vmcs_writel(CR4_READ_SHADOW, cr4);
vmcs_writel(GUEST_CR4, hw_cr4);
return 0;
}
static void vmx_get_segment(struct kvm_vcpu *vcpu,