RISC-V: KVM: Introduce struct kvm_gstage_mapping

Introduce struct kvm_gstage_mapping which represents a g-stage
mapping at a particular g-stage page table level. Also, update
the kvm_riscv_gstage_map() to return the g-stage mapping upon
success.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Tested-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Nutty Liu <liujingqi@lanxincomputing.com>
Link: https://lore.kernel.org/r/20250618113532.471448-10-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>

Author: avpatel

arch/riscv/include/asm/kvm_mmu.h

@@ -8,14 +8,21 @@
 
 #include <linux/kvm_types.h>
 
+struct kvm_gstage_mapping {
+	gpa_t addr;
+	pte_t pte;
+	u32 level;
+};
+
 int kvm_riscv_gstage_ioremap(struct kvm *kvm, gpa_t gpa,
 			     phys_addr_t hpa, unsigned long size,
 			     bool writable, bool in_atomic);
 void kvm_riscv_gstage_iounmap(struct kvm *kvm, gpa_t gpa,
 			      unsigned long size);
 int kvm_riscv_gstage_map(struct kvm_vcpu *vcpu,
 			 struct kvm_memory_slot *memslot,
-			 gpa_t gpa, unsigned long hva, bool is_write);
+			 gpa_t gpa, unsigned long hva, bool is_write,
+			 struct kvm_gstage_mapping *out_map);
 int kvm_riscv_gstage_alloc_pgd(struct kvm *kvm);
 void kvm_riscv_gstage_free_pgd(struct kvm *kvm);
 void kvm_riscv_gstage_update_hgatp(struct kvm_vcpu *vcpu);

arch/riscv/kvm/mmu.c

@@ -135,18 +135,18 @@ static void gstage_remote_tlb_flush(struct kvm *kvm, u32 level, gpa_t addr)
 	kvm_riscv_hfence_gvma_vmid_gpa(kvm, -1UL, 0, addr, BIT(order), order);
 }
 
-static int gstage_set_pte(struct kvm *kvm, u32 level,
-			   struct kvm_mmu_memory_cache *pcache,
-			   gpa_t addr, const pte_t *new_pte)
+static int gstage_set_pte(struct kvm *kvm,
+			  struct kvm_mmu_memory_cache *pcache,
+			  const struct kvm_gstage_mapping *map)
 {
 	u32 current_level = gstage_pgd_levels - 1;
 	pte_t *next_ptep = (pte_t *)kvm->arch.pgd;
-	pte_t *ptep = &next_ptep[gstage_pte_index(addr, current_level)];
+	pte_t *ptep = &next_ptep[gstage_pte_index(map->addr, current_level)];
 
-	if (current_level < level)
+	if (current_level < map->level)
 		return -EINVAL;
 
-	while (current_level != level) {
+	while (current_level != map->level) {
 		if (gstage_pte_leaf(ptep))
 			return -EEXIST;
 
@@ -165,13 +165,13 @@ static int gstage_set_pte(struct kvm *kvm, u32 level,
 		}
 
 		current_level--;
-		ptep = &next_ptep[gstage_pte_index(addr, current_level)];
+		ptep = &next_ptep[gstage_pte_index(map->addr, current_level)];
 	}
 
-	if (pte_val(*ptep) != pte_val(*new_pte)) {
-		set_pte(ptep, *new_pte);
+	if (pte_val(*ptep) != pte_val(map->pte)) {
+		set_pte(ptep, map->pte);
 		if (gstage_pte_leaf(ptep))
-			gstage_remote_tlb_flush(kvm, current_level, addr);
+			gstage_remote_tlb_flush(kvm, current_level, map->addr);
 	}
 
 	return 0;
@@ -181,14 +181,16 @@ static int gstage_map_page(struct kvm *kvm,
 			   struct kvm_mmu_memory_cache *pcache,
 			   gpa_t gpa, phys_addr_t hpa,
 			   unsigned long page_size,
-			   bool page_rdonly, bool page_exec)
+			   bool page_rdonly, bool page_exec,
+			   struct kvm_gstage_mapping *out_map)
 {
-	int ret;
-	u32 level = 0;
-	pte_t new_pte;
 	pgprot_t prot;
+	int ret;
 
-	ret = gstage_page_size_to_level(page_size, &level);
+	out_map->addr = gpa;
+	out_map->level = 0;
+
+	ret = gstage_page_size_to_level(page_size, &out_map->level);
 	if (ret)
 		return ret;
 
@@ -216,10 +218,10 @@ static int gstage_map_page(struct kvm *kvm,
 		else
 			prot = PAGE_WRITE;
 	}
-	new_pte = pfn_pte(PFN_DOWN(hpa), prot);
-	new_pte = pte_mkdirty(new_pte);
+	out_map->pte = pfn_pte(PFN_DOWN(hpa), prot);
+	out_map->pte = pte_mkdirty(out_map->pte);
 
-	return gstage_set_pte(kvm, level, pcache, gpa, &new_pte);
+	return gstage_set_pte(kvm, pcache, out_map);
 }
 
 enum gstage_op {
@@ -352,30 +354,32 @@ int kvm_riscv_gstage_ioremap(struct kvm *kvm, gpa_t gpa,
 			     phys_addr_t hpa, unsigned long size,
 			     bool writable, bool in_atomic)
 {
-	pte_t pte;
 	int ret = 0;
 	unsigned long pfn;
 	phys_addr_t addr, end;
 	struct kvm_mmu_memory_cache pcache = {
 		.gfp_custom = (in_atomic) ? GFP_ATOMIC | __GFP_ACCOUNT : 0,
 		.gfp_zero = __GFP_ZERO,
 	};
+	struct kvm_gstage_mapping map;
 
 	end = (gpa + size + PAGE_SIZE - 1) & PAGE_MASK;
 	pfn = __phys_to_pfn(hpa);
 
 	for (addr = gpa; addr < end; addr += PAGE_SIZE) {
-		pte = pfn_pte(pfn, PAGE_KERNEL_IO);
+		map.addr = addr;
+		map.pte = pfn_pte(pfn, PAGE_KERNEL_IO);
+		map.level = 0;
 
 		if (!writable)
-			pte = pte_wrprotect(pte);
+			map.pte = pte_wrprotect(map.pte);
 
 		ret = kvm_mmu_topup_memory_cache(&pcache, gstage_pgd_levels);
 		if (ret)
 			goto out;
 
 		spin_lock(&kvm->mmu_lock);
-		ret = gstage_set_pte(kvm, 0, &pcache, addr, &pte);
+		ret = gstage_set_pte(kvm, &pcache, &map);
 		spin_unlock(&kvm->mmu_lock);
 		if (ret)
 			goto out;
@@ -593,7 +597,8 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
 
 int kvm_riscv_gstage_map(struct kvm_vcpu *vcpu,
 			 struct kvm_memory_slot *memslot,
-			 gpa_t gpa, unsigned long hva, bool is_write)
+			 gpa_t gpa, unsigned long hva, bool is_write,
+			 struct kvm_gstage_mapping *out_map)
 {
 	int ret;
 	kvm_pfn_t hfn;
@@ -608,6 +613,9 @@ int kvm_riscv_gstage_map(struct kvm_vcpu *vcpu,
 	unsigned long vma_pagesize, mmu_seq;
 	struct page *page;
 
+	/* Setup initial state of output mapping */
+	memset(out_map, 0, sizeof(*out_map));
+
 	/* We need minimum second+third level pages */
 	ret = kvm_mmu_topup_memory_cache(pcache, gstage_pgd_levels);
 	if (ret) {
@@ -677,10 +685,10 @@ int kvm_riscv_gstage_map(struct kvm_vcpu *vcpu,
 	if (writable) {
 		mark_page_dirty(kvm, gfn);
 		ret = gstage_map_page(kvm, pcache, gpa, hfn << PAGE_SHIFT,
-				      vma_pagesize, false, true);
+				      vma_pagesize, false, true, out_map);
 	} else {
 		ret = gstage_map_page(kvm, pcache, gpa, hfn << PAGE_SHIFT,
-				      vma_pagesize, true, true);
+				      vma_pagesize, true, true, out_map);
 	}
 
 	if (ret)

arch/riscv/kvm/vcpu_exit.c

@@ -15,6 +15,7 @@
 static int gstage_page_fault(struct kvm_vcpu *vcpu, struct kvm_run *run,
 			     struct kvm_cpu_trap *trap)
 {
+	struct kvm_gstage_mapping host_map;
 	struct kvm_memory_slot *memslot;
 	unsigned long hva, fault_addr;
 	bool writable;
@@ -43,7 +44,7 @@ static int gstage_page_fault(struct kvm_vcpu *vcpu, struct kvm_run *run,
 	}
 
 	ret = kvm_riscv_gstage_map(vcpu, memslot, fault_addr, hva,
-		(trap->scause == EXC_STORE_GUEST_PAGE_FAULT) ? true : false);
+		(trap->scause == EXC_STORE_GUEST_PAGE_FAULT) ? true : false, &host_map);
 	if (ret < 0)
 		return ret;