RISC-V: KVM: Add G-stage ioremap() and iounmap() functions

The in-kernel AIA IMSIC support requires on-demand mapping / unmapping
of Guest IMSIC address to Host IMSIC guest files. To help achieve this,
we add kvm_riscv_stage2_ioremap() and kvm_riscv_stage2_iounmap() functions.
These new functions for updating G-stage page table mappings will be called
in atomic context so we have special "in_atomic" parameter for this purpose.
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Anup Patel <anup@brainfault.org>

arch/riscv/include/asm/kvm_host.h

@@ -284,6 +284,11 @@ void kvm_riscv_hfence_vvma_gva(struct kvm *kvm,
 void kvm_riscv_hfence_vvma_all(struct kvm *kvm,
 			       unsigned long hbase, unsigned long hmask);
 
+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);

arch/riscv/kvm/mmu.c

@@ -343,8 +343,9 @@ static void gstage_wp_memory_region(struct kvm *kvm, int slot)
 	kvm_flush_remote_tlbs(kvm);
 }
 
-static int gstage_ioremap(struct kvm *kvm, gpa_t gpa, phys_addr_t hpa,
-			  unsigned long size, bool writable)
+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;
@@ -353,6 +354,7 @@ static int gstage_ioremap(struct kvm *kvm, gpa_t gpa, phys_addr_t hpa,
 	struct kvm_mmu_memory_cache pcache;
 
 	memset(&pcache, 0, sizeof(pcache));
+	pcache.gfp_custom = (in_atomic) ? GFP_ATOMIC | __GFP_ACCOUNT : 0;
 	pcache.gfp_zero = __GFP_ZERO;
 
 	end = (gpa + size + PAGE_SIZE - 1) & PAGE_MASK;
@@ -382,6 +384,13 @@ static int gstage_ioremap(struct kvm *kvm, gpa_t gpa, phys_addr_t hpa,
 	return ret;
 }
 
+void kvm_riscv_gstage_iounmap(struct kvm *kvm, gpa_t gpa, unsigned long size)
+{
+	spin_lock(&kvm->mmu_lock);
+	gstage_unmap_range(kvm, gpa, size, false);
+	spin_unlock(&kvm->mmu_lock);
+}
+
 void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
 					     struct kvm_memory_slot *slot,
 					     gfn_t gfn_offset,
@@ -517,8 +526,9 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 				goto out;
 			}
 
-			ret = gstage_ioremap(kvm, gpa, pa,
-					     vm_end - vm_start, writable);
+			ret = kvm_riscv_gstage_ioremap(kvm, gpa, pa,
+						       vm_end - vm_start,
+						       writable, false);
 			if (ret)
 				break;
 		}