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Commit 5e1746d6 authored by Nadav Har'El's avatar Nadav Har'El Committed by Avi Kivity
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KVM: nVMX: Allow setting the VMXE bit in CR4 



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: default avatarNadav Har'El <nyh@il.ibm.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent ec378aee

arch/x86/include/asm/kvm_host.h

+1 −1
Original line number Diff line number Diff line
@@ -555,7 +555,7 @@ struct kvm_x86_ops { 
	void (*decache_cr4_guest_bits)(struct kvm_vcpu *vcpu);

	void (*set_cr0)(struct kvm_vcpu *vcpu, unsigned long cr0);

	void (*set_cr3)(struct kvm_vcpu *vcpu, unsigned long cr3);

	void (*set_cr4)(struct kvm_vcpu *vcpu, unsigned long cr4);

	int (*set_cr4)(struct kvm_vcpu *vcpu, unsigned long cr4);

	void (*set_efer)(struct kvm_vcpu *vcpu, u64 efer);

	void (*get_idt)(struct kvm_vcpu *vcpu, struct desc_ptr *dt);

	void (*set_idt)(struct kvm_vcpu *vcpu, struct desc_ptr *dt);

arch/x86/kvm/svm.c

+5 −1
Original line number Diff line number Diff line
@@ -1496,11 +1496,14 @@ static void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0) 
	update_cr0_intercept(svm);

}



static void svm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)

static int svm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)

{

	unsigned long host_cr4_mce = read_cr4() & X86_CR4_MCE;

	unsigned long old_cr4 = to_svm(vcpu)->vmcb->save.cr4;



	if (cr4 & X86_CR4_VMXE)

		return 1;



	if (npt_enabled && ((old_cr4 ^ cr4) & X86_CR4_PGE))

		svm_flush_tlb(vcpu);
@@ -1510,6 +1513,7 @@ static void svm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) 
	cr4 |= host_cr4_mce;

	to_svm(vcpu)->vmcb->save.cr4 = cr4;

	mark_dirty(to_svm(vcpu)->vmcb, VMCB_CR);

	return 0;

}



static void svm_set_segment(struct kvm_vcpu *vcpu,

arch/x86/kvm/vmx.c

+15 −2
Original line number Diff line number Diff line
@@ -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,

arch/x86/kvm/x86.c

+1 −3
Original line number Diff line number Diff line
@@ -615,11 +615,9 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) 
				   kvm_read_cr3(vcpu)))

		return 1;



	if (cr4 & X86_CR4_VMXE)

	if (kvm_x86_ops->set_cr4(vcpu, cr4))

		return 1;



	kvm_x86_ops->set_cr4(vcpu, cr4);



	if ((cr4 ^ old_cr4) & pdptr_bits)

		kvm_mmu_reset_context(vcpu);