[RFC PATCH v2 48/58] iommu/arm-smmu-v3-kvm: Add function to topup IOMMU allocator

[Mostafa Saleh <smostafa@google.com>]

The hypervisor returns requests for memory allocation in HVCs
encoded in the return registers.

Add a function that checks those returns and topup the IOMMU
alloctor in response to requests, and a macro that calls
this function around calling an HVC.

Signed-off-by: Mostafa Saleh <smostafa@google.com>
---
 .../iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c   | 40 +++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c
index e4a5bdc830bc..dab2d59b5a88 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c
@@ -4,6 +4,7 @@
  *
  * Copyright (C) 2022 Linaro Ltd.
  */
+#include <asm/kvm_pkvm.h>
 #include <asm/kvm_mmu.h>
 
 #include <linux/of_platform.h>
@@ -28,6 +29,45 @@ static size_t				kvm_arm_smmu_cur;
 static size_t				kvm_arm_smmu_count;
 static struct hyp_arm_smmu_v3_device	*kvm_arm_smmu_array;
 
+static int kvm_arm_smmu_topup_memcache(struct arm_smccc_res *res, gfp_t gfp)
+{
+	struct kvm_hyp_req req;
+
+	hyp_reqs_smccc_decode(res, &req);
+
+	if ((res->a1 == -ENOMEM) && (req.type != KVM_HYP_REQ_TYPE_MEM)) {
+		/*
+		 * There is no way for drivers to populate hyp_alloc requests,
+		 * so -ENOMEM + no request indicates that.
+		 */
+		return __pkvm_topup_hyp_alloc(1);
+	} else if (req.type != KVM_HYP_REQ_TYPE_MEM) {
+		return -EBADE;
+	}
+
+	if (req.mem.dest == REQ_MEM_DEST_HYP_IOMMU) {
+		return __pkvm_topup_hyp_alloc_mgt_gfp(HYP_ALLOC_MGT_IOMMU_ID,
+						      req.mem.nr_pages,
+						      req.mem.sz_alloc,
+						      gfp);
+	} else if (req.mem.dest == REQ_MEM_DEST_HYP_ALLOC) {
+		/* Fill hyp alloc*/
+		return __pkvm_topup_hyp_alloc(req.mem.nr_pages);
+	}
+
+	pr_err("Bogus mem request");
+	return -EBADE;
+}
+
+#define kvm_call_hyp_nvhe_mc(...)					\
+({									\
+	struct arm_smccc_res __res;					\
+	do {								\
+		__res = kvm_call_hyp_nvhe_smccc(__VA_ARGS__);		\
+	} while (__res.a1 && !kvm_arm_smmu_topup_memcache(&__res, GFP_KERNEL));\
+	__res.a1;							\
+})
+
 static bool kvm_arm_smmu_validate_features(struct arm_smmu_device *smmu)
 {
 	unsigned int required_features =
-- 
2.47.0.338.g60cca15819-goog