Commit c2fe3cd4 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: x86: Move vendor CR4 validity check to dedicated kvm_x86_ops hook 



Split out VMX's checks on CR4.VMXE to a dedicated hook, .is_valid_cr4(),
and invoke the new hook from kvm_valid_cr4().  This fixes an issue where
KVM_SET_SREGS would return success while failing to actually set CR4.

Fixing the issue by explicitly checking kvm_x86_ops.set_cr4()'s return
in __set_sregs() is not a viable option as KVM has already stuffed a
variety of vCPU state.

Note, kvm_valid_cr4() and is_valid_cr4() have different return types and
inverted semantics.  This will be remedied in a future patch.

Fixes: 5e1746d6 ("KVM: nVMX: Allow setting the VMXE bit in CR4")
Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20201007014417.29276-5-sean.j.christopherson@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 311a0659

arch/x86/include/asm/kvm_host.h

+2 −1
Original line number Diff line number Diff line
@@ -1115,7 +1115,8 @@ struct kvm_x86_ops { 
			    struct kvm_segment *var, int seg);

	void (*get_cs_db_l_bits)(struct kvm_vcpu *vcpu, int *db, int *l);

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

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

	bool (*is_valid_cr4)(struct kvm_vcpu *vcpu, unsigned long cr0);

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

	int (*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/svm.c

+7 −2
Original line number Diff line number Diff line
@@ -1682,7 +1682,12 @@ void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0) 
	update_cr0_intercept(svm);

}



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

static bool svm_is_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)

{

	return true;

}



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

{

	unsigned long host_cr4_mce = cr4_read_shadow() & X86_CR4_MCE;

	unsigned long old_cr4 = to_svm(vcpu)->vmcb->save.cr4;
@@ -1696,7 +1701,6 @@ int svm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) 
	cr4 |= host_cr4_mce;

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

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

	return 0;

}



static void svm_set_segment(struct kvm_vcpu *vcpu,
@@ -4212,6 +4216,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = { 
	.get_cpl = svm_get_cpl,

	.get_cs_db_l_bits = kvm_get_cs_db_l_bits,

	.set_cr0 = svm_set_cr0,

	.is_valid_cr4 = svm_is_valid_cr4,

	.set_cr4 = svm_set_cr4,

	.set_efer = svm_set_efer,

	.get_idt = svm_get_idt,

arch/x86/kvm/svm/svm.h

+1 −1
Original line number Diff line number Diff line
@@ -358,7 +358,7 @@ void svm_vcpu_free_msrpm(u32 *msrpm); 


int svm_set_efer(struct kvm_vcpu *vcpu, u64 efer);

void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0);

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

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

void svm_flush_tlb(struct kvm_vcpu *vcpu);

void disable_nmi_singlestep(struct vcpu_svm *svm);

bool svm_smi_blocked(struct kvm_vcpu *vcpu);

arch/x86/kvm/vmx/nested.c

+1 −1
Original line number Diff line number Diff line
@@ -4814,7 +4814,7 @@ static int handle_vmon(struct kvm_vcpu *vcpu) 
	/*

	 * The Intel VMX Instruction Reference lists a bunch of bits that are

	 * prerequisite to running VMXON, most notably cr4.VMXE must be set to

	 * 1 (see vmx_set_cr4() for when we allow the guest to set this).

	 * 1 (see vmx_is_valid_cr4() for when we allow the guest to set this).

	 * Otherwise, we should fail with #UD.  But most faulting conditions

	 * have already been checked by hardware, prior to the VM-exit for

	 * VMXON.  We do test guest cr4.VMXE because processor CR4 always has

arch/x86/kvm/vmx/vmx.c

+18 −13
Original line number Diff line number Diff line
@@ -3095,7 +3095,23 @@ static void vmx_load_mmu_pgd(struct kvm_vcpu *vcpu, unsigned long pgd, 
		vmcs_writel(GUEST_CR3, guest_cr3);

}



int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)

static bool vmx_is_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)

{

	/*

	 * We operate under the default treatment of SMM, so VMX cannot be

	 * enabled under SMM.  Note, whether or not VMXE is allowed at all is

	 * handled by kvm_valid_cr4().

	 */

	if ((cr4 & X86_CR4_VMXE) && is_smm(vcpu))

		return false;



	if (to_vmx(vcpu)->nested.vmxon && !nested_cr4_valid(vcpu, cr4))

		return false;



	return true;

}



void vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)

{

	struct vcpu_vmx *vmx = to_vmx(vcpu);

	/*
@@ -3123,17 +3139,6 @@ int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) 
		}

	}



	/*

	 * We operate under the default treatment of SMM, so VMX cannot be

	 * enabled under SMM.  Note, whether or not VMXE is allowed at all is

	 * handled by kvm_valid_cr4().

	 */

	if ((cr4 & X86_CR4_VMXE) && is_smm(vcpu))

		return 1;



	if (vmx->nested.vmxon && !nested_cr4_valid(vcpu, cr4))

		return 1;



	vcpu->arch.cr4 = cr4;

	kvm_register_mark_available(vcpu, VCPU_EXREG_CR4);
@@ -3164,7 +3169,6 @@ int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) 


	vmcs_writel(CR4_READ_SHADOW, cr4);

	vmcs_writel(GUEST_CR4, hw_cr4);

	return 0;

}



void vmx_get_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg)
@@ -7612,6 +7616,7 @@ static struct kvm_x86_ops vmx_x86_ops __initdata = { 
	.get_cpl = vmx_get_cpl,

	.get_cs_db_l_bits = vmx_get_cs_db_l_bits,

	.set_cr0 = vmx_set_cr0,

	.is_valid_cr4 = vmx_is_valid_cr4,

	.set_cr4 = vmx_set_cr4,

	.set_efer = vmx_set_efer,

	.get_idt = vmx_get_idt,

CRA Git | Maintained and supported by SUSTech CRA and CCSE