x86: kvm: mmu: use ept a/d in vmcs02 iff used in vmcs12
EPT A/D was enabled in the vmcs02 EPTP regardless of the vmcs12's EPTP
value. The problem is that enabling A/D changes the behavior of L2's
x86 page table walks as seen by L1. With A/D enabled, x86 page table
walks are always treated as EPT writes.
Commit ae1e2d1082ae ("kvm: nVMX: support EPT accessed/dirty bits",
2017-03-30) tried to work around this problem by clearing the write
bit in the exit qualification for EPT violations triggered by page
walks. However, that fixup introduced the opposite bug: page-table walks
that actually set x86 A/D bits were *missing* the write bit in the exit
qualification.
This patch fixes the problem by disabling EPT A/D in the shadow MMU
when EPT A/D is disabled in vmcs12's EPTP.
Signed-off-by: Peter Feiner <pfeiner@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index b102a86..fb04712 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -910,8 +910,9 @@ static void nested_release_page_clean(struct page *page)
kvm_release_page_clean(page);
}
+static bool nested_ept_ad_enabled(struct kvm_vcpu *vcpu);
static unsigned long nested_ept_get_cr3(struct kvm_vcpu *vcpu);
-static u64 construct_eptp(unsigned long root_hpa);
+static u64 construct_eptp(struct kvm_vcpu *vcpu, unsigned long root_hpa);
static bool vmx_xsaves_supported(void);
static int vmx_set_tss_addr(struct kvm *kvm, unsigned int addr);
static void vmx_set_segment(struct kvm_vcpu *vcpu,
@@ -4013,7 +4014,7 @@ static inline void __vmx_flush_tlb(struct kvm_vcpu *vcpu, int vpid)
if (enable_ept) {
if (!VALID_PAGE(vcpu->arch.mmu.root_hpa))
return;
- ept_sync_context(construct_eptp(vcpu->arch.mmu.root_hpa));
+ ept_sync_context(construct_eptp(vcpu, vcpu->arch.mmu.root_hpa));
} else {
vpid_sync_context(vpid);
}
@@ -4188,14 +4189,15 @@ static void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
vmx->emulation_required = emulation_required(vcpu);
}
-static u64 construct_eptp(unsigned long root_hpa)
+static u64 construct_eptp(struct kvm_vcpu *vcpu, unsigned long root_hpa)
{
u64 eptp;
/* TODO write the value reading from MSR */
eptp = VMX_EPT_DEFAULT_MT |
VMX_EPT_DEFAULT_GAW << VMX_EPT_GAW_EPTP_SHIFT;
- if (enable_ept_ad_bits)
+ if (enable_ept_ad_bits &&
+ (!is_guest_mode(vcpu) || nested_ept_ad_enabled(vcpu)))
eptp |= VMX_EPT_AD_ENABLE_BIT;
eptp |= (root_hpa & PAGE_MASK);
@@ -4209,7 +4211,7 @@ static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
guest_cr3 = cr3;
if (enable_ept) {
- eptp = construct_eptp(cr3);
+ eptp = construct_eptp(vcpu, cr3);
vmcs_write64(EPT_POINTER, eptp);
if (is_paging(vcpu) || is_guest_mode(vcpu))
guest_cr3 = kvm_read_cr3(vcpu);
@@ -6214,17 +6216,6 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu)
exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
- if (is_guest_mode(vcpu)
- && !(exit_qualification & EPT_VIOLATION_GVA_TRANSLATED)) {
- /*
- * Fix up exit_qualification according to whether guest
- * page table accesses are reads or writes.
- */
- u64 eptp = nested_ept_get_cr3(vcpu);
- if (!(eptp & VMX_EPT_AD_ENABLE_BIT))
- exit_qualification &= ~EPT_VIOLATION_ACC_WRITE;
- }
-
/*
* EPT violation happened while executing iret from NMI,
* "blocked by NMI" bit has to be set before next VM entry.
@@ -6447,7 +6438,7 @@ void vmx_enable_tdp(void)
enable_ept_ad_bits ? VMX_EPT_DIRTY_BIT : 0ull,
0ull, VMX_EPT_EXECUTABLE_MASK,
cpu_has_vmx_ept_execute_only() ? 0ull : VMX_EPT_READABLE_MASK,
- enable_ept_ad_bits ? 0ull : VMX_EPT_RWX_MASK);
+ VMX_EPT_RWX_MASK);
ept_set_mmio_spte_mask();
kvm_enable_tdp();
@@ -9393,6 +9384,11 @@ static void nested_ept_inject_page_fault(struct kvm_vcpu *vcpu,
vmcs12->guest_physical_address = fault->address;
}
+static bool nested_ept_ad_enabled(struct kvm_vcpu *vcpu)
+{
+ return nested_ept_get_cr3(vcpu) & VMX_EPT_AD_ENABLE_BIT;
+}
+
/* Callbacks for nested_ept_init_mmu_context: */
static unsigned long nested_ept_get_cr3(struct kvm_vcpu *vcpu)
@@ -9403,18 +9399,18 @@ static unsigned long nested_ept_get_cr3(struct kvm_vcpu *vcpu)
static int nested_ept_init_mmu_context(struct kvm_vcpu *vcpu)
{
- u64 eptp;
+ bool wants_ad;
WARN_ON(mmu_is_nested(vcpu));
- eptp = nested_ept_get_cr3(vcpu);
- if ((eptp & VMX_EPT_AD_ENABLE_BIT) && !enable_ept_ad_bits)
+ wants_ad = nested_ept_ad_enabled(vcpu);
+ if (wants_ad && !enable_ept_ad_bits)
return 1;
kvm_mmu_unload(vcpu);
kvm_init_shadow_ept_mmu(vcpu,
to_vmx(vcpu)->nested.nested_vmx_ept_caps &
VMX_EPT_EXECUTE_ONLY_BIT,
- eptp & VMX_EPT_AD_ENABLE_BIT);
+ wants_ad);
vcpu->arch.mmu.set_cr3 = vmx_set_cr3;
vcpu->arch.mmu.get_cr3 = nested_ept_get_cr3;
vcpu->arch.mmu.inject_page_fault = nested_ept_inject_page_fault;