From: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
We can have discrepancies between the nested stage 2 page table and the
shadow one in a couple of cases. For example, the guest hypervisor can
mark a page writable but the host hypervisor maps the page read-only in
the shadow page table, if using something like KSM on the host level.
In this case, a write fault is handled directly by the host hypervisor.
But we could also simply have a read-only page mapped read-only in both
tables, in which case the host hypervisor cannot do anything else than
telling the guest hypervisor about the fault.
Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
Signed-off-by: Jintack Lim <jintack.lim@xxxxxxxxxx>
---
arch/arm/include/asm/kvm_mmu.h | 7 +++++++
arch/arm64/include/asm/kvm_mmu.h | 2 ++
arch/arm64/kvm/mmu-nested.c | 22 ++++++++++++++++++++++
virt/kvm/arm/mmu.c | 7 +++++++
4 files changed, 38 insertions(+)
diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index 6a22846..1c5b652 100644
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -237,6 +237,13 @@ static inline int kvm_walk_nested_s2(struct kvm_vcpu *vcpu, phys_addr_t gipa,
return 0;
}
+static inline int kvm_s2_handle_perm_fault(struct kvm_vcpu *vcpu,
+ phys_addr_t fault_ipa,
+ struct kvm_s2_trans *trans)
+{
+ return 0;
+}
+
static inline void kvm_nested_s2_unmap(struct kvm_vcpu *vcpu) { }
static inline void kvm_nested_s2_free(struct kvm *kvm) { }
static inline void kvm_nested_s2_wp(struct kvm *kvm) { }
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 425e4a2..239bb89 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -337,6 +337,8 @@ struct kvm_s2_trans {
void update_nested_s2_mmu(struct kvm_vcpu *vcpu);
int kvm_walk_nested_s2(struct kvm_vcpu *vcpu, phys_addr_t gipa,
struct kvm_s2_trans *result);
+int kvm_s2_handle_perm_fault(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
+ struct kvm_s2_trans *trans);
void kvm_nested_s2_unmap(struct kvm_vcpu *vcpu);
void kvm_nested_s2_free(struct kvm *kvm);
void kvm_nested_s2_wp(struct kvm *kvm);
diff --git a/arch/arm64/kvm/mmu-nested.c b/arch/arm64/kvm/mmu-nested.c
index 75570cc..a440d7b 100644
--- a/arch/arm64/kvm/mmu-nested.c
+++ b/arch/arm64/kvm/mmu-nested.c
@@ -271,6 +271,28 @@ int kvm_walk_nested_s2(struct kvm_vcpu *vcpu, phys_addr_t gipa,
return walk_nested_s2_pgd(vcpu, gipa, &wi, result);
}
+/*
+ * Returns non-zero if permission fault is handled by injecting it to the next
+ * level hypervisor.
+ */
+int kvm_s2_handle_perm_fault(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
+ struct kvm_s2_trans *trans)
+{
+ unsigned long fault_status = kvm_vcpu_trap_get_fault_type(vcpu);
+ bool write_fault = kvm_is_write_fault(vcpu);
+
+ if (fault_status != FSC_PERM)
+ return 0;
+
+ if ((write_fault && !trans->writable) ||
+ (!write_fault && !trans->readable)) {
+ trans->esr = esr_s2_fault(vcpu, trans->level, ESR_ELx_FSC_PERM);
+ return 1;
+ }
+
+ return 0;
+}
+
/* expects kvm->mmu_lock to be held */
void kvm_nested_s2_wp(struct kvm *kvm)
{
diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index 74941ad..4fb7b3b 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1591,6 +1591,13 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run)
if (ret)
goto out_unlock;
+ nested_trans.esr = 0;
+ ret = kvm_s2_handle_perm_fault(vcpu, fault_ipa, &nested_trans);
+ if (nested_trans.esr)
+ kvm_inject_s2_fault(vcpu, nested_trans.esr);
+ if (ret)
+ goto out_unlock;
+
ipa = nested_trans.output;
}
--
1.9.1
