[PATCH v2 06/18] KVM: arm64: Add topup interface for the pKVM heap allocator

[Vincent Donnefort <vdonnefort@google.com>]

Introduce a host HVC interface and a host side helper to allow refilling
the pKVM heap allocator.

Signed-off-by: Vincent Donnefort <vdonnefort@google.com>

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 043495f7fc78..681b7bf8ac08 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -114,6 +114,7 @@ enum __kvm_host_smccc_func {
 	__KVM_HOST_SMCCC_FUNC___pkvm_vcpu_load,
 	__KVM_HOST_SMCCC_FUNC___pkvm_vcpu_put,
 	__KVM_HOST_SMCCC_FUNC___pkvm_tlb_flush_vmid,
+	__KVM_HOST_SMCCC_FUNC___pkvm_hyp_topup,
 
 	MARKER(__KVM_HOST_SMCCC_FUNC_MAX)
 };
diff --git a/arch/arm64/include/asm/kvm_pkvm.h b/arch/arm64/include/asm/kvm_pkvm.h
index 74fedd9c5ff0..870f7870bb62 100644
--- a/arch/arm64/include/asm/kvm_pkvm.h
+++ b/arch/arm64/include/asm/kvm_pkvm.h
@@ -17,6 +17,10 @@
 
 #define HYP_MEMBLOCK_REGIONS 128
 
+enum pkvm_topup_id {
+	PKVM_TOPUP_HYP_ALLOC,
+};
+
 int pkvm_init_host_vm(struct kvm *kvm, unsigned long type);
 int pkvm_create_hyp_vm(struct kvm *kvm);
 bool pkvm_hyp_vm_is_created(struct kvm *kvm);
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index d3c69de698f4..e270a974fa37 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -15,6 +15,7 @@
 #include <asm/kvm_hypevents.h>
 #include <asm/kvm_mmu.h>
 
+#include <nvhe/alloc.h>
 #include <nvhe/ffa.h>
 #include <nvhe/mem_protect.h>
 #include <nvhe/mm.h>
@@ -632,6 +633,30 @@ static void handle___pkvm_finalize_teardown_vm(struct kvm_cpu_context *host_ctxt
 	cpu_reg(host_ctxt, 1) = __pkvm_finalize_teardown_vm(handle);
 }
 
+static void handle___pkvm_hyp_topup(struct kvm_cpu_context *host_ctxt)
+{
+	DECLARE_REG(enum pkvm_topup_id, id, host_ctxt, 1);
+	DECLARE_REG(phys_addr_t, head, host_ctxt, 2);
+	DECLARE_REG(unsigned long, nr_pages, host_ctxt, 3);
+	struct kvm_hyp_memcache host_mc = {
+		.head = head,
+		.nr_pages = nr_pages,
+	};
+	int ret;
+
+	switch (id) {
+	case PKVM_TOPUP_HYP_ALLOC:
+		ret = hyp_alloc_topup(&host_mc);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	cpu_reg(host_ctxt, 1) = ret;
+	cpu_reg(host_ctxt, 2) = host_mc.head;
+	cpu_reg(host_ctxt, 3) = host_mc.nr_pages;
+}
+
 static void handle___tracing_load(struct kvm_cpu_context *host_ctxt)
 {
 	DECLARE_REG(unsigned long, desc_hva, host_ctxt, 1);
@@ -762,6 +787,7 @@ static const hcall_t host_hcall[] = {
 	HANDLE_FUNC(__pkvm_vcpu_load),
 	HANDLE_FUNC(__pkvm_vcpu_put),
 	HANDLE_FUNC(__pkvm_tlb_flush_vmid),
+	HANDLE_FUNC(__pkvm_hyp_topup),
 };
 
 static void handle_host_hcall(struct kvm_cpu_context *host_ctxt)
diff --git a/arch/arm64/kvm/pkvm.c b/arch/arm64/kvm/pkvm.c
index 8324a6a1bc48..e2c8714e8ccc 100644
--- a/arch/arm64/kvm/pkvm.c
+++ b/arch/arm64/kvm/pkvm.c
@@ -85,6 +85,33 @@ void __init kvm_hyp_reserve(void)
 		 hyp_mem_base);
 }
 
+static int pkvm_hyp_topup(enum pkvm_topup_id id, unsigned long nr_pages)
+{
+	struct kvm_hyp_memcache mc;
+	struct arm_smccc_res res;
+	int ret;
+
+	init_hyp_memcache(&mc);
+	ret = topup_hyp_memcache(&mc, nr_pages);
+	if (ret)
+		goto err;
+
+	arm_smccc_1_1_hvc(KVM_HOST_SMCCC_FUNC(__pkvm_hyp_topup), id, mc.head,
+			  mc.nr_pages, &res);
+	if (WARN_ON_ONCE(res.a0 != SMCCC_RET_SUCCESS)) {
+		ret = -EINVAL;
+		goto err;
+	}
+
+	ret = res.a1;
+	mc.head = res.a2;
+	mc.nr_pages = res.a3;
+
+err:
+	free_hyp_memcache(&mc);
+	return ret;
+}
+
 static void __pkvm_destroy_hyp_vm(struct kvm *kvm)
 {
 	if (pkvm_hyp_vm_is_created(kvm)) {
-- 
2.55.0.rc2.803.g1fd1e6609c-goog