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KVM: nVMX: Introduce 'EVMPTR_MAP_PENDING' post-migration state

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Unlike regular set_current_vmptr(), nested_vmx_handle_enlightened_vmptrld()
can not be called directly from vmx_set_nested_state() as KVM may not have
all the information yet (e.g. HV_X64_MSR_VP_ASSIST_PAGE MSR may not be
restored yet). Enlightened VMCS is mapped later while getting nested state
pages. In the meantime, vmx->nested.hv_evmcs_vmptr remains 'EVMPTR_INVALID'
and it's indistinguishable from 'evmcs is not in use' case. This leads to
certain issues, in particular, if KVM_GET_NESTED_STATE is called right
after KVM_SET_NESTED_STATE, KVM_STATE_NESTED_EVMCS flag in the resulting
state will be unset (and such state will later fail to load).

Introduce 'EVMPTR_MAP_PENDING' state to detect not-yet-mapped eVMCS after
restore. With this, the 'is_guest_mode(vcpu)' hack in vmx_has_valid_vmcs12()
is no longer needed.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210526132026.270394-6-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Vitaly Kuznetsov 2021-05-26 15:20:20 +02:00 committed by Paolo Bonzini
parent 25641cafab
commit 278499686b
3 changed files with 9 additions and 11 deletions
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3
arch/x86/kvm/vmx/evmcs.h
View file

@ -198,10 +198,11 @@ static inline void evmcs_touch_msr_bitmap(void) {}
#endif /* IS_ENABLED(CONFIG_HYPERV) */
#define EVMPTR_INVALID (-1ULL)
#define EVMPTR_MAP_PENDING (-2ULL)
static inline bool evmptr_is_valid(u64 evmptr)
{
return evmptr != EVMPTR_INVALID;
return evmptr != EVMPTR_INVALID && evmptr != EVMPTR_MAP_PENDING;
}
enum nested_evmptrld_status {

6
arch/x86/kvm/vmx/nested.c
View file

@ -3102,7 +3102,7 @@ static bool nested_get_evmcs_page(struct kvm_vcpu *vcpu)
* properly reflected.
*/
if (vmx->nested.enlightened_vmcs_enabled &&
!evmptr_is_valid(vmx->nested.hv_evmcs_vmptr)) {
vmx->nested.hv_evmcs_vmptr == EVMPTR_MAP_PENDING) {
enum nested_evmptrld_status evmptrld_status =
nested_vmx_handle_enlightened_vmptrld(vcpu, false);
@ -6095,7 +6095,8 @@ static int vmx_get_nested_state(struct kvm_vcpu *vcpu,
if (vmx_has_valid_vmcs12(vcpu)) {
kvm_state.size += sizeof(user_vmx_nested_state->vmcs12);
if (evmptr_is_valid(vmx->nested.hv_evmcs_vmptr))
/* 'hv_evmcs_vmptr' can also be EVMPTR_MAP_PENDING here */
if (vmx->nested.hv_evmcs_vmptr != EVMPTR_INVALID)
kvm_state.flags |= KVM_STATE_NESTED_EVMCS;
if (is_guest_mode(vcpu) &&
@ -6294,6 +6295,7 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu,
* restored yet. EVMCS will be mapped from
* nested_get_vmcs12_pages().
*/
vmx->nested.hv_evmcs_vmptr = EVMPTR_MAP_PENDING;
kvm_make_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu);
} else {
return -EINVAL;

11
arch/x86/kvm/vmx/nested.h
View file

@ -56,14 +56,9 @@ static inline int vmx_has_valid_vmcs12(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
/*
* In case we do two consecutive get/set_nested_state()s while L2 was
* running hv_evmcs may end up not being mapped (we map it from
* nested_vmx_run()/vmx_vcpu_run()). Check is_guest_mode() as we always
* have vmcs12 if it is true.
*/
return is_guest_mode(vcpu) || vmx->nested.current_vmptr != -1ull ||
evmptr_is_valid(vmx->nested.hv_evmcs_vmptr);
/* 'hv_evmcs_vmptr' can also be EVMPTR_MAP_PENDING here */
return vmx->nested.current_vmptr != -1ull ||
vmx->nested.hv_evmcs_vmptr != EVMPTR_INVALID;
}
static inline u16 nested_get_vpid02(struct kvm_vcpu *vcpu)