Loading CR3 as part of emulating vmentry is different from regular CR3 loads,
as implemented in kvm_set_cr3, in several ways.
* different rules are followed to check CR3 and it is desirable for the caller
to distinguish between the possible failures
* PDPTRs are not loaded if PAE paging and nested EPT are both enabled
* many MMU operations are not necessary
This patch introduces nested_vmx_load_cr3 suitable for CR3 loads as part of
nested vmentry and vmexit, and makes use of it on the nested vmentry path.
Signed-off-by: Ladi Prosek <lprosek@xxxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/vmx.c | 59 +++++++++++++++++++++++++++++------------
arch/x86/kvm/x86.c | 3 ++-
3 files changed, 45 insertions(+), 18 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index bdde807..9ec06a3 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1062,6 +1062,7 @@ unsigned int kvm_mmu_calculate_mmu_pages(struct kvm *kvm);
void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned int kvm_nr_mmu_pages);
int load_pdptrs(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, unsigned long cr3);
+bool pdptrs_changed(struct kvm_vcpu *vcpu);
int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa,
const void *val, int bytes);
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 70598a1..58dc7f1 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -9796,6 +9796,44 @@ static int nested_vmx_store_msr(struct kvm_vcpu *vcpu, u64 gpa, u32 count)
}
/*
+ * Load guest's/host's cr3 at nested entry/exit. nested_ept is true if we are
+ * emulating VM entry into a guest with EPT enabled.
+ * Returns 0 on success, 1 on failure. Invalid state exit qualification code
+ * is assigned to entry_failure_code on failure.
+ */
+static int nested_vmx_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool nested_ept,
+ unsigned long *entry_failure_code)
+{
+ unsigned long invalid_mask;
+
+ if (cr3 != kvm_read_cr3(vcpu) || (!nested_ept && pdptrs_changed(vcpu))) {
+ invalid_mask = (~0ULL) << cpuid_maxphyaddr(vcpu);
+ if (cr3 & invalid_mask) {
+ *entry_failure_code = ENTRY_FAIL_DEFAULT;
+ return 1;
+ }
+
+ /*
+ * If PAE paging and EPT are both on, CR3 is not used by the CPU and
+ * must not be dereferenced.
+ */
+ if (!is_long_mode(vcpu) && is_pae(vcpu) && is_paging(vcpu) &&
+ !nested_ept) {
+ if (!load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3)) {
+ *entry_failure_code = ENTRY_FAIL_PDPTE;
+ return 1;
+ }
+ }
+
+ vcpu->arch.cr3 = cr3;
+ __set_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail);
+ }
+
+ kvm_mmu_reset_context(vcpu);
+ return 0;
+}
+
+/*
* prepare_vmcs02 is called when the L1 guest hypervisor runs its nested
* L2 guest. L1 has a vmcs for L2 (vmcs12), and this function "merges" it
* with L0's requirements for its guest (a.k.a. vmcs01), so we can run the L2
@@ -10118,23 +10156,10 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
vmx_set_cr4(vcpu, vmcs12->guest_cr4);
vmcs_writel(CR4_READ_SHADOW, nested_read_cr4(vmcs12));
- /*
- * Shadow page tables on either EPT or shadow page tables.
- * If PAE and EPT are both on, CR3 is not used by the CPU and must not
- * be dereferenced.
- */
- if (is_pae(vcpu) && is_paging(vcpu) && !is_long_mode(vcpu) &&
- nested_ept_enabled) {
- vcpu->arch.cr3 = vmcs12->guest_cr3;
- __set_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail);
- } else {
- if (kvm_set_cr3(vcpu, vmcs12->guest_cr3)) {
- *entry_failure_code = ENTRY_FAIL_DEFAULT;
- return 1;
- }
- }
-
- kvm_mmu_reset_context(vcpu);
+ /* Shadow page tables on either EPT or shadow page tables. */
+ if (nested_vmx_load_cr3(vcpu, vmcs12->guest_cr3, nested_ept_enabled,
+ entry_failure_code))
+ return 1;
if (!enable_ept)
vcpu->arch.walk_mmu->inject_page_fault = vmx_inject_page_fault_nested;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 78f6061..e4e06f9 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -573,7 +573,7 @@ int load_pdptrs(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, unsigned long cr3)
}
EXPORT_SYMBOL_GPL(load_pdptrs);
-static bool pdptrs_changed(struct kvm_vcpu *vcpu)
+bool pdptrs_changed(struct kvm_vcpu *vcpu)
{
u64 pdpte[ARRAY_SIZE(vcpu->arch.walk_mmu->pdptrs)];
bool changed = true;
@@ -599,6 +599,7 @@ static bool pdptrs_changed(struct kvm_vcpu *vcpu)
return changed;
}
+EXPORT_SYMBOL_GPL(pdptrs_changed);
int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
{
--
2.7.4
--
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