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kvm: nVMX: Add support for "VMWRITE to any supported field"

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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: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Jim Mattson 2018-05-29 09:11:33 -07:00 committed by Paolo Bonzini
parent a943ac50d1
commit f4160e459c
1 changed files with 60 additions and 9 deletions
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69
arch/x86/kvm/vmx.c
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@ -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));
@ -8136,23 +8163,42 @@ 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];
field_value = __vmcs_readl(field);
vmcs12_write_any(&vmx->vcpu, field, field_value);
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);
@ -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);