[PATCH v2 13/18] KVM: arm64: Introduce __pkvm_host_wrprotect_guest()

[Quentin Perret]

Introduce a new hypercall to remove the write permission from a
non-protected guest stage-2 mapping. This will be used for e.g. enabling
dirty logging.

Signed-off-by: Quentin Perret <qperret@xxxxxxxxxx>
---
 arch/arm64/include/asm/kvm_asm.h              |  1 +
 arch/arm64/kvm/hyp/include/nvhe/mem_protect.h |  1 +
 arch/arm64/kvm/hyp/nvhe/hyp-main.c            | 24 +++++++++++++++++++
 arch/arm64/kvm/hyp/nvhe/mem_protect.c         | 19 +++++++++++++++
 4 files changed, 45 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 5d51933e44fb..4d7d20ea03df 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -68,6 +68,7 @@ enum __kvm_host_smccc_func {
 	__KVM_HOST_SMCCC_FUNC___pkvm_host_share_guest,
 	__KVM_HOST_SMCCC_FUNC___pkvm_host_unshare_guest,
 	__KVM_HOST_SMCCC_FUNC___pkvm_host_relax_guest_perms,
+	__KVM_HOST_SMCCC_FUNC___pkvm_host_wrprotect_guest,
 	__KVM_HOST_SMCCC_FUNC___kvm_adjust_pc,
 	__KVM_HOST_SMCCC_FUNC___kvm_vcpu_run,
 	__KVM_HOST_SMCCC_FUNC___kvm_flush_vm_context,
diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
index db0dd83c2457..8658b5932473 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
@@ -42,6 +42,7 @@ int __pkvm_host_unshare_ffa(u64 pfn, u64 nr_pages);
 int __pkvm_host_share_guest(u64 pfn, u64 gfn, struct pkvm_hyp_vcpu *vcpu, enum kvm_pgtable_prot prot);
 int __pkvm_host_unshare_guest(u64 gfn, struct pkvm_hyp_vm *hyp_vm);
 int __pkvm_host_relax_guest_perms(u64 gfn, enum kvm_pgtable_prot prot, struct pkvm_hyp_vcpu *vcpu);
+int __pkvm_host_wrprotect_guest(u64 gfn, struct pkvm_hyp_vm *hyp_vm);
 
 bool addr_is_memory(phys_addr_t phys);
 int host_stage2_idmap_locked(phys_addr_t addr, u64 size, enum kvm_pgtable_prot prot);
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index 60dd56bbd743..3feaf2119e51 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -286,6 +286,29 @@ static void handle___pkvm_host_relax_guest_perms(struct kvm_cpu_context *host_ct
 	cpu_reg(host_ctxt, 1) = ret;
 }
 
+static void handle___pkvm_host_wrprotect_guest(struct kvm_cpu_context *host_ctxt)
+{
+	DECLARE_REG(pkvm_handle_t, handle, host_ctxt, 1);
+	DECLARE_REG(u64, gfn, host_ctxt, 2);
+	struct pkvm_hyp_vm *hyp_vm;
+	int ret = -EINVAL;
+
+	if (!is_protected_kvm_enabled())
+		goto out;
+
+	hyp_vm = get_pkvm_hyp_vm(handle);
+	if (!hyp_vm)
+		goto out;
+	if (pkvm_hyp_vm_is_protected(hyp_vm))
+		goto put_hyp_vm;
+
+	ret = __pkvm_host_wrprotect_guest(gfn, hyp_vm);
+put_hyp_vm:
+	put_pkvm_hyp_vm(hyp_vm);
+out:
+	cpu_reg(host_ctxt, 1) = ret;
+}
+
 static void handle___kvm_adjust_pc(struct kvm_cpu_context *host_ctxt)
 {
 	DECLARE_REG(struct kvm_vcpu *, vcpu, host_ctxt, 1);
@@ -498,6 +521,7 @@ static const hcall_t host_hcall[] = {
 	HANDLE_FUNC(__pkvm_host_share_guest),
 	HANDLE_FUNC(__pkvm_host_unshare_guest),
 	HANDLE_FUNC(__pkvm_host_relax_guest_perms),
+	HANDLE_FUNC(__pkvm_host_wrprotect_guest),
 	HANDLE_FUNC(__kvm_adjust_pc),
 	HANDLE_FUNC(__kvm_vcpu_run),
 	HANDLE_FUNC(__kvm_flush_vm_context),
diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index d4b28e93e790..89312d7cde2a 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -1503,3 +1503,22 @@ int __pkvm_host_relax_guest_perms(u64 gfn, enum kvm_pgtable_prot prot, struct pk
 
 	return ret;
 }
+
+int __pkvm_host_wrprotect_guest(u64 gfn, struct pkvm_hyp_vm *vm)
+{
+	u64 ipa = hyp_pfn_to_phys(gfn);
+	u64 phys;
+	int ret;
+
+	host_lock_component();
+	guest_lock_component(vm);
+
+	ret = __check_host_unshare_guest(vm, &phys, ipa);
+	if (!ret)
+		ret = kvm_pgtable_stage2_wrprotect(&vm->pgt, ipa, PAGE_SIZE);
+
+	guest_unlock_component(vm);
+	host_unlock_component();
+
+	return ret;
+}
-- 
2.47.0.338.g60cca15819-goog