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Commit f4160e45 authored by Jim Mattson's avatar Jim Mattson Committed by Paolo Bonzini
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kvm: nVMX: Add support for "VMWRITE to any supported field" 



Add support for "VMWRITE to any supported field in the VMCS" and
enable this feature by default in L1's IA32_VMX_MISC MSR. If userspace
clears the VMX capability bit, the old behavior will be restored.

Note that this feature is a prerequisite for kvm in L1 to use VMCS
shadowing, once that feature is available.

Signed-off-by: default avatarJim Mattson <jmattson@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent a943ac50

arch/x86/kvm/vmx.c

+60 −9
Original line number Diff line number Diff line
@@ -1694,6 +1694,17 @@ static inline unsigned nested_cpu_vmx_misc_cr3_count(struct kvm_vcpu *vcpu) 
	return vmx_misc_cr3_count(to_vmx(vcpu)->nested.msrs.misc_low);

}



/*

 * Do the virtual VMX capability MSRs specify that L1 can use VMWRITE

 * to modify any valid field of the VMCS, or are the VM-exit

 * information fields read-only?

 */

static inline bool nested_cpu_has_vmwrite_any_field(struct kvm_vcpu *vcpu)

{

	return to_vmx(vcpu)->nested.msrs.misc_low &

		MSR_IA32_VMX_MISC_VMWRITE_SHADOW_RO_FIELDS;

}



static inline bool nested_cpu_has(struct vmcs12 *vmcs12, u32 bit)

{

	return vmcs12->cpu_based_vm_exec_control & bit;
@@ -3311,6 +3322,7 @@ static void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, bool apicv) 
		msrs->misc_high);

	msrs->misc_low &= VMX_MISC_SAVE_EFER_LMA;

	msrs->misc_low |=

		MSR_IA32_VMX_MISC_VMWRITE_SHADOW_RO_FIELDS |

		VMX_MISC_EMULATED_PREEMPTION_TIMER_RATE |

		VMX_MISC_ACTIVITY_HLT;

	msrs->misc_high = 0;
@@ -3484,6 +3496,15 @@ static int vmx_restore_vmx_misc(struct vcpu_vmx *vmx, u64 data) 


	vmx->nested.msrs.misc_low = data;

	vmx->nested.msrs.misc_high = data >> 32;



	/*

	 * If L1 has read-only VM-exit information fields, use the

	 * less permissive vmx_vmwrite_bitmap to specify write

	 * permissions for the shadow VMCS.

	 */

	if (enable_shadow_vmcs && !nested_cpu_has_vmwrite_any_field(&vmx->vcpu))

		vmcs_write64(VMWRITE_BITMAP, __pa(vmx_vmwrite_bitmap));



	return 0;

}
@@ -6154,8 +6175,14 @@ static void vmx_vcpu_setup(struct vcpu_vmx *vmx) 
	int i;



	if (enable_shadow_vmcs) {

		/*

		 * At vCPU creation, "VMWRITE to any supported field

		 * in the VMCS" is supported, so use the more

		 * permissive vmx_vmread_bitmap to specify both read

		 * and write permissions for the shadow VMCS.

		 */

		vmcs_write64(VMREAD_BITMAP, __pa(vmx_vmread_bitmap));

		vmcs_write64(VMWRITE_BITMAP, __pa(vmx_vmwrite_bitmap));

		vmcs_write64(VMWRITE_BITMAP, __pa(vmx_vmread_bitmap));

	}

	if (cpu_has_vmx_msr_bitmap())

		vmcs_write64(MSR_BITMAP, __pa(vmx->vmcs01.msr_bitmap));
@@ -8136,24 +8163,43 @@ static inline int vmcs12_write_any(struct kvm_vcpu *vcpu, 


}



/*

 * Copy the writable VMCS shadow fields back to the VMCS12, in case

 * they have been modified by the L1 guest. Note that the "read-only"

 * VM-exit information fields are actually writable if the vCPU is

 * configured to support "VMWRITE to any supported field in the VMCS."

 */

static void copy_shadow_to_vmcs12(struct vcpu_vmx *vmx)

{

	int i;

	const u16 *fields[] = {

		shadow_read_write_fields,

		shadow_read_only_fields

	};

	const int max_fields[] = {

		max_shadow_read_write_fields,

		max_shadow_read_only_fields

	};

	int i, q;

	unsigned long field;

	u64 field_value;

	struct vmcs *shadow_vmcs = vmx->vmcs01.shadow_vmcs;

	const u16 *fields = shadow_read_write_fields;

	const int num_fields = max_shadow_read_write_fields;



	preempt_disable();



	vmcs_load(shadow_vmcs);



	for (i = 0; i < num_fields; i++) {

		field = fields[i];

	for (q = 0; q < ARRAY_SIZE(fields); q++) {

		for (i = 0; i < max_fields[q]; i++) {

			field = fields[q][i];

			field_value = __vmcs_readl(field);

			vmcs12_write_any(&vmx->vcpu, field, field_value);

		}

		/*

		 * Skip the VM-exit information fields if they are read-only.

		 */

		if (!nested_cpu_has_vmwrite_any_field(&vmx->vcpu))

			break;

	}



	vmcs_clear(shadow_vmcs);

	vmcs_load(vmx->loaded_vmcs->vmcs);
@@ -8286,7 +8332,12 @@ static int handle_vmwrite(struct kvm_vcpu *vcpu) 




	field = kvm_register_readl(vcpu, (((vmx_instruction_info) >> 28) & 0xf));

	if (vmcs_field_readonly(field)) {

	/*

	 * If the vCPU supports "VMWRITE to any supported field in the

	 * VMCS," then the "read-only" fields are actually read/write.

	 */

	if (vmcs_field_readonly(field) &&

	    !nested_cpu_has_vmwrite_any_field(vcpu)) {

		nested_vmx_failValid(vcpu,

			VMXERR_VMWRITE_READ_ONLY_VMCS_COMPONENT);

		return kvm_skip_emulated_instruction(vcpu);