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KVM: nVMX: Emulate EPTP switching for the L1 hypervisor
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When L2 uses vmfunc, L0 utilizes the associated vmexit to
emulate a switching of the ept pointer by reloading the
guest MMU.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Bandan Das <bsd@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
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Bandan Das authored and Paolo Bonzini committed Aug 7, 2017
1 parent 27c42a1 commit 41ab937
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Showing 2 changed files with 124 additions and 6 deletions.
6 changes: 6 additions & 0 deletions arch/x86/include/asm/vmx.h
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Original file line number Diff line number Diff line change
Expand Up @@ -115,6 +115,10 @@
#define VMX_MISC_SAVE_EFER_LMA 0x00000020
#define VMX_MISC_ACTIVITY_HLT 0x00000040

/* VMFUNC functions */
#define VMX_VMFUNC_EPTP_SWITCHING 0x00000001
#define VMFUNC_EPTP_ENTRIES 512

static inline u32 vmx_basic_vmcs_revision_id(u64 vmx_basic)
{
return vmx_basic & GENMASK_ULL(30, 0);
Expand Down Expand Up @@ -200,6 +204,8 @@ enum vmcs_field {
EOI_EXIT_BITMAP2_HIGH = 0x00002021,
EOI_EXIT_BITMAP3 = 0x00002022,
EOI_EXIT_BITMAP3_HIGH = 0x00002023,
EPTP_LIST_ADDRESS = 0x00002024,
EPTP_LIST_ADDRESS_HIGH = 0x00002025,
VMREAD_BITMAP = 0x00002026,
VMWRITE_BITMAP = 0x00002028,
XSS_EXIT_BITMAP = 0x0000202C,
Expand Down
124 changes: 118 additions & 6 deletions arch/x86/kvm/vmx.c
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Original file line number Diff line number Diff line change
Expand Up @@ -249,6 +249,7 @@ struct __packed vmcs12 {
u64 eoi_exit_bitmap1;
u64 eoi_exit_bitmap2;
u64 eoi_exit_bitmap3;
u64 eptp_list_address;
u64 xss_exit_bitmap;
u64 guest_physical_address;
u64 vmcs_link_pointer;
Expand Down Expand Up @@ -771,6 +772,7 @@ static const unsigned short vmcs_field_to_offset_table[] = {
FIELD64(EOI_EXIT_BITMAP1, eoi_exit_bitmap1),
FIELD64(EOI_EXIT_BITMAP2, eoi_exit_bitmap2),
FIELD64(EOI_EXIT_BITMAP3, eoi_exit_bitmap3),
FIELD64(EPTP_LIST_ADDRESS, eptp_list_address),
FIELD64(XSS_EXIT_BITMAP, xss_exit_bitmap),
FIELD64(GUEST_PHYSICAL_ADDRESS, guest_physical_address),
FIELD64(VMCS_LINK_POINTER, vmcs_link_pointer),
Expand Down Expand Up @@ -1388,6 +1390,13 @@ static inline bool nested_cpu_has_vmfunc(struct vmcs12 *vmcs12)
return nested_cpu_has2(vmcs12, SECONDARY_EXEC_ENABLE_VMFUNC);
}

static inline bool nested_cpu_has_eptp_switching(struct vmcs12 *vmcs12)
{
return nested_cpu_has_vmfunc(vmcs12) &&
(vmcs12->vm_function_control &
VMX_VMFUNC_EPTP_SWITCHING);
}

static inline bool is_nmi(u32 intr_info)
{
return (intr_info & (INTR_INFO_INTR_TYPE_MASK | INTR_INFO_VALID_MASK))
Expand Down Expand Up @@ -2839,7 +2848,12 @@ static void nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx)
if (cpu_has_vmx_vmfunc()) {
vmx->nested.nested_vmx_secondary_ctls_high |=
SECONDARY_EXEC_ENABLE_VMFUNC;
vmx->nested.nested_vmx_vmfunc_controls = 0;
/*
* Advertise EPTP switching unconditionally
* since we emulate it
*/
vmx->nested.nested_vmx_vmfunc_controls =
VMX_VMFUNC_EPTP_SWITCHING;
}

/*
Expand Down Expand Up @@ -7862,6 +7876,88 @@ static int handle_preemption_timer(struct kvm_vcpu *vcpu)
return 1;
}

static bool valid_ept_address(struct kvm_vcpu *vcpu, u64 address)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
u64 mask = address & 0x7;
int maxphyaddr = cpuid_maxphyaddr(vcpu);

/* Check for memory type validity */
switch (mask) {
case 0:
if (!(vmx->nested.nested_vmx_ept_caps & VMX_EPTP_UC_BIT))
return false;
break;
case 6:
if (!(vmx->nested.nested_vmx_ept_caps & VMX_EPTP_WB_BIT))
return false;
break;
default:
return false;
}

/* Bits 5:3 must be 3 */
if (((address >> VMX_EPT_GAW_EPTP_SHIFT) & 0x7) != VMX_EPT_DEFAULT_GAW)
return false;

/* Reserved bits should not be set */
if (address >> maxphyaddr || ((address >> 7) & 0x1f))
return false;

/* AD, if set, should be supported */
if ((address & VMX_EPT_AD_ENABLE_BIT)) {
if (!(vmx->nested.nested_vmx_ept_caps & VMX_EPT_AD_BIT))
return false;
}

return true;
}

static int nested_vmx_eptp_switching(struct kvm_vcpu *vcpu,
struct vmcs12 *vmcs12)
{
u32 index = vcpu->arch.regs[VCPU_REGS_RCX];
u64 address;
bool accessed_dirty;
struct kvm_mmu *mmu = vcpu->arch.walk_mmu;

if (!nested_cpu_has_eptp_switching(vmcs12) ||
!nested_cpu_has_ept(vmcs12))
return 1;

if (index >= VMFUNC_EPTP_ENTRIES)
return 1;


if (kvm_vcpu_read_guest_page(vcpu, vmcs12->eptp_list_address >> PAGE_SHIFT,
&address, index * 8, 8))
return 1;

accessed_dirty = !!(address & VMX_EPT_AD_ENABLE_BIT);

/*
* If the (L2) guest does a vmfunc to the currently
* active ept pointer, we don't have to do anything else
*/
if (vmcs12->ept_pointer != address) {
if (!valid_ept_address(vcpu, address))
return 1;

kvm_mmu_unload(vcpu);
mmu->ept_ad = accessed_dirty;
mmu->base_role.ad_disabled = !accessed_dirty;
vmcs12->ept_pointer = address;
/*
* TODO: Check what's the correct approach in case
* mmu reload fails. Currently, we just let the next
* reload potentially fail
*/
kvm_mmu_reload(vcpu);
}

return 0;
}

static int handle_vmfunc(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
Expand All @@ -7881,7 +7977,16 @@ static int handle_vmfunc(struct kvm_vcpu *vcpu)
vmcs12 = get_vmcs12(vcpu);
if ((vmcs12->vm_function_control & (1 << function)) == 0)
goto fail;
WARN_ONCE(1, "VMCS12 VM function control should have been zero");

switch (function) {
case 0:
if (nested_vmx_eptp_switching(vcpu, vmcs12))
goto fail;
break;
default:
goto fail;
}
return kvm_skip_emulated_instruction(vcpu);

fail:
nested_vmx_vmexit(vcpu, vmx->exit_reason,
Expand Down Expand Up @@ -10524,10 +10629,17 @@ static int check_vmentry_prereqs(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
vmx->nested.nested_vmx_entry_ctls_high))
return VMXERR_ENTRY_INVALID_CONTROL_FIELD;

if (nested_cpu_has_vmfunc(vmcs12) &&
(vmcs12->vm_function_control &
~vmx->nested.nested_vmx_vmfunc_controls))
return VMXERR_ENTRY_INVALID_CONTROL_FIELD;
if (nested_cpu_has_vmfunc(vmcs12)) {
if (vmcs12->vm_function_control &
~vmx->nested.nested_vmx_vmfunc_controls)
return VMXERR_ENTRY_INVALID_CONTROL_FIELD;

if (nested_cpu_has_eptp_switching(vmcs12)) {
if (!nested_cpu_has_ept(vmcs12) ||
!page_address_valid(vcpu, vmcs12->eptp_list_address))
return VMXERR_ENTRY_INVALID_CONTROL_FIELD;
}
}

if (vmcs12->cr3_target_count > nested_cpu_vmx_misc_cr3_count(vcpu))
return VMXERR_ENTRY_INVALID_CONTROL_FIELD;
Expand Down

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