[PATCH v2 2/6] KVM: nVMX: delay loading of PDPTRs to KVM_REQ_GET_NESTED_STATE_PAGES

From: Maxim Levitsky
Date: Mon Apr 26 2021 - 07:14:29 EST


Similar to the rest of guest page accesses after a migration,
this access should be delayed to KVM_REQ_GET_NESTED_STATE_PAGES.

Signed-off-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
---
arch/x86/kvm/vmx/nested.c | 23 ++++++++++++++++++-----
1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 00339d624c92..764781ab805b 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -1105,7 +1105,8 @@ static bool nested_vmx_transition_mmu_sync(struct kvm_vcpu *vcpu)
* Exit Qualification (for a VM-Entry consistency check VM-Exit) is assigned to
* @entry_failure_code.
*/
-static int nested_vmx_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool nested_ept,
+static int nested_vmx_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3,
+ bool nested_ept, bool reload_pdptrs,
enum vm_entry_failure_code *entry_failure_code)
{
if (CC(kvm_vcpu_is_illegal_gpa(vcpu, cr3))) {
@@ -1117,7 +1118,7 @@ static int nested_vmx_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool ne
* If PAE paging and EPT are both on, CR3 is not used by the CPU and
* must not be dereferenced.
*/
- if (!nested_ept && is_pae_paging(vcpu) &&
+ if (reload_pdptrs && !nested_ept && is_pae_paging(vcpu) &&
(cr3 != kvm_read_cr3(vcpu) || pdptrs_changed(vcpu))) {
if (CC(!load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3))) {
*entry_failure_code = ENTRY_FAIL_PDPTE;
@@ -2488,6 +2489,7 @@ static void prepare_vmcs02_rare(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12)
* is assigned to entry_failure_code on failure.
*/
static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
+ bool from_vmentry,
enum vm_entry_failure_code *entry_failure_code)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -2572,7 +2574,7 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,

/* Shadow page tables on either EPT or shadow page tables. */
if (nested_vmx_load_cr3(vcpu, vmcs12->guest_cr3, nested_cpu_has_ept(vmcs12),
- entry_failure_code))
+ from_vmentry, entry_failure_code))
return -EINVAL;

/*
@@ -3120,6 +3122,17 @@ static bool nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
struct page *page;
u64 hpa;

+ if (!nested_cpu_has_ept(vmcs12) && is_pae_paging(vcpu)) {
+ /*
+ * Reload the guest's PDPTRs since after a migration
+ * the guest CR3 might be restored prior to setting the nested
+ * state which can lead to a load of wrong PDPTRs.
+ */
+ if (CC(!load_pdptrs(vcpu, vcpu->arch.walk_mmu, vcpu->arch.cr3)))
+ return false;
+ }
+
+
if (nested_cpu_has2(vmcs12, SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES)) {
/*
* Translate L1 physical address to host physical
@@ -3356,7 +3369,7 @@ enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETTING)
vcpu->arch.tsc_offset += vmcs12->tsc_offset;

- if (prepare_vmcs02(vcpu, vmcs12, &entry_failure_code)) {
+ if (prepare_vmcs02(vcpu, vmcs12, from_vmentry, &entry_failure_code)) {
exit_reason.basic = EXIT_REASON_INVALID_STATE;
vmcs12->exit_qualification = entry_failure_code;
goto vmentry_fail_vmexit_guest_mode;
@@ -4205,7 +4218,7 @@ static void load_vmcs12_host_state(struct kvm_vcpu *vcpu,
* Only PDPTE load can fail as the value of cr3 was checked on entry and
* couldn't have changed.
*/
- if (nested_vmx_load_cr3(vcpu, vmcs12->host_cr3, false, &ignored))
+ if (nested_vmx_load_cr3(vcpu, vmcs12->host_cr3, false, true, &ignored))
nested_vmx_abort(vcpu, VMX_ABORT_LOAD_HOST_PDPTE_FAIL);

nested_vmx_transition_tlb_flush(vcpu, vmcs12, false);
--
2.26.2