[PATCH RFC v15 25/30] virt: gunyah: Enable demand paging

[Elliot Berman]

Tell resource manager to enable demand paging and wire vCPU faults to
provide the backing folio when a guestmemfd is bound to the faulting
access.

Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx>
---
 drivers/virt/gunyah/guest_memfd.c | 92 +++++++++++++++++++++++++++++++++++++++
 drivers/virt/gunyah/gunyah_vcpu.c | 39 ++++++++++++++++-
 drivers/virt/gunyah/vm_mgr.c      | 17 ++++++++
 drivers/virt/gunyah/vm_mgr.h      |  3 ++
 include/linux/gunyah.h            |  2 +
 5 files changed, 152 insertions(+), 1 deletion(-)

diff --git a/drivers/virt/gunyah/guest_memfd.c b/drivers/virt/gunyah/guest_memfd.c
index 419ed617bd0b..206ce51c9a7d 100644
--- a/drivers/virt/gunyah/guest_memfd.c
+++ b/drivers/virt/gunyah/guest_memfd.c
@@ -732,3 +732,95 @@ int gunyah_gmem_reclaim_parcel(struct gunyah_vm *ghvm,
 	up_read(&ghvm->mem_lock);
 	return 0;
 }
+
+int gunyah_gmem_setup_demand_paging(struct gunyah_vm *ghvm)
+{
+	struct gunyah_rm_mem_entry *entries;
+	struct gunyah_gmem_binding *b;
+	unsigned long index = 0;
+	u32 count = 0, i;
+	int ret = 0;
+
+	down_read(&ghvm->mem_lock);
+	mt_for_each(&ghvm->mem_layout, b, index, ULONG_MAX)
+		if (gunyah_guest_mem_is_lend(ghvm, b->flags))
+			count++;
+
+	if (!count)
+		goto out;
+
+	entries = kcalloc(count, sizeof(*entries), GFP_KERNEL);
+	if (!entries) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	index = i = 0;
+	mt_for_each(&ghvm->mem_layout, b, index, ULONG_MAX) {
+		if (!gunyah_guest_mem_is_lend(ghvm, b->flags))
+			continue;
+		entries[i].phys_addr = cpu_to_le64(gunyah_gfn_to_gpa(b->gfn));
+		entries[i].size = cpu_to_le64(b->nr << PAGE_SHIFT);
+		if (++i == count)
+			break;
+	}
+
+	ret = gunyah_rm_vm_set_demand_paging(ghvm->rm, ghvm->vmid, i, entries);
+	kfree(entries);
+out:
+	up_read(&ghvm->mem_lock);
+	return ret;
+}
+
+int gunyah_gmem_demand_page(struct gunyah_vm *ghvm, u64 gpa, bool write)
+{
+	unsigned long gfn = gunyah_gpa_to_gfn(gpa);
+	struct gunyah_gmem_binding *b;
+	struct folio *folio;
+	int ret;
+
+	down_read(&ghvm->mem_lock);
+	b = mtree_load(&ghvm->mem_layout, gfn);
+	if (!b) {
+		up_read(&ghvm->mem_lock);
+		return -ENOENT;
+	}
+
+	if (write && !(b->flags & GUNYAH_MEM_ALLOW_WRITE))
+		return -EPERM;
+
+	folio = gunyah_gmem_get_folio(b->inode, gunyah_gfn_to_off(b, gfn));
+	if (IS_ERR(folio)) {
+		up_read(&ghvm->mem_lock);
+		pr_err_ratelimited(
+			"Failed to obtain memory for guest addr %016llx: %ld\n",
+			gpa, PTR_ERR(folio));
+		return PTR_ERR(folio);
+	}
+
+	if (gunyah_guest_mem_is_lend(ghvm, b->flags) && folio_mapped(folio)) {
+		ret = -EPERM;
+		goto out;
+	}
+
+	gfn = gunyah_off_to_gfn(b, folio_index(folio));
+
+	ret = gunyah_vm_provide_folio(ghvm, folio, gfn,
+				      !gunyah_guest_mem_is_lend(ghvm, b->flags),
+				      !!(b->flags & GUNYAH_MEM_ALLOW_WRITE));
+	if (ret) {
+		pr_err_ratelimited(
+			"Failed to provide folio for guest addr: %016llx: %d\n",
+			gpa, ret);
+		goto out;
+	}
+
+	if (gunyah_guest_mem_is_lend(ghvm, b->flags))
+		folio_set_private(folio);
+out:
+	folio_unlock(folio);
+	folio_put(folio);
+	up_read(&ghvm->mem_lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gunyah_gmem_demand_page);
diff --git a/drivers/virt/gunyah/gunyah_vcpu.c b/drivers/virt/gunyah/gunyah_vcpu.c
index aa40f5977cbf..1952a1797430 100644
--- a/drivers/virt/gunyah/gunyah_vcpu.c
+++ b/drivers/virt/gunyah/gunyah_vcpu.c
@@ -91,6 +91,29 @@ static irqreturn_t gunyah_vcpu_irq_handler(int irq, void *data)
 	return IRQ_HANDLED;
 }
 
+static bool gunyah_handle_page_fault(
+	struct gunyah_vcpu *vcpu, u64 state_data[3],
+	const struct gunyah_hypercall_vcpu_run_resp *vcpu_run_resp)
+{
+	int ret = 0;
+	u64 addr = vcpu_run_resp->state_data[0];
+	bool write = !!vcpu_run_resp->state_data[1];
+
+	ret = gunyah_gmem_demand_page(vcpu->ghvm, addr, write);
+	if (ret) {
+		if (ret != -ENOENT)
+			pr_warn_ratelimited(
+				"Failed to provide guest address for: %08llx: %d\n",
+				addr, ret);
+
+		vcpu->vcpu_run->page_fault.resume_action = GUNYAH_VCPU_RESUME_FAULT;
+		vcpu->vcpu_run->page_fault.attempt = ret;
+		vcpu->vcpu_run->page_fault.phys_addr = addr;
+		vcpu->vcpu_run->exit_reason = GUNYAH_VCPU_EXIT_PAGE_FAULT;
+	}
+	return !!ret;
+}
+
 static bool
 gunyah_handle_mmio(struct gunyah_vcpu *vcpu, u64 state_data[3],
 		   const struct gunyah_hypercall_vcpu_run_resp *vcpu_run_resp)
@@ -103,6 +126,12 @@ gunyah_handle_mmio(struct gunyah_vcpu *vcpu, u64 state_data[3],
 	if (WARN_ON(len > sizeof(u64)))
 		len = sizeof(u64);
 
+	if (!gunyah_gmem_demand_page(vcpu->ghvm, addr,
+				     vcpu->vcpu_run->mmio.is_write)) {
+		state_data[1] = GUNYAH_ADDRSPACE_VMMIO_ACTION_RETRY;
+		return true;
+	}
+
 	if (vcpu_run_resp->state == GUNYAH_VCPU_ADDRSPACE_VMMIO_READ) {
 		vcpu->vcpu_run->mmio.is_write = 0;
 		/* Record that we need to give vCPU user's supplied value next gunyah_vcpu_run() */
@@ -120,7 +149,8 @@ gunyah_handle_mmio(struct gunyah_vcpu *vcpu, u64 state_data[3],
 		vcpu->state = GUNYAH_VCPU_MMIO_WRITE;
 	}
 
-	vcpu->vcpu_run->mmio.phys_addr = addr;
+	vcpu->vcpu_run->mmio.resume_action = 0;
+	vcpu->mmio_addr = vcpu->vcpu_run->mmio.phys_addr = addr;
 	vcpu->vcpu_run->mmio.len = len;
 	vcpu->vcpu_run->exit_reason = GUNYAH_VCPU_EXIT_MMIO;
 
@@ -144,6 +174,8 @@ static int gunyah_handle_mmio_resume(struct gunyah_vcpu *vcpu, u64 state_data[3]
 		state_data[1] = GUNYAH_ADDRSPACE_VMMIO_ACTION_FAULT;
 		break;
 	case GUNYAH_VCPU_RESUME_RETRY:
+		gunyah_gmem_demand_page(vcpu->ghvm, vcpu->mmio_addr,
+					vcpu->state == GUNYAH_VCPU_MMIO_WRITE);
 		state_data[1] = GUNYAH_ADDRSPACE_VMMIO_ACTION_RETRY;
 		break;
 	default:
@@ -300,6 +332,11 @@ static int gunyah_vcpu_run(struct gunyah_vcpu *vcpu)
 							&vcpu_run_resp))
 					goto out;
 				break;
+			case GUNYAH_VCPU_ADDRSPACE_PAGE_FAULT:
+				if (gunyah_handle_page_fault(vcpu, resume_data,
+							     &vcpu_run_resp))
+					goto out;
+				break;
 			default:
 				pr_warn_ratelimited(
 					"Unknown vCPU state: %llx\n",
diff --git a/drivers/virt/gunyah/vm_mgr.c b/drivers/virt/gunyah/vm_mgr.c
index 8f8d962c9f8c..0bb2b6a461a5 100644
--- a/drivers/virt/gunyah/vm_mgr.c
+++ b/drivers/virt/gunyah/vm_mgr.c
@@ -653,6 +653,23 @@ static int gunyah_vm_start(struct gunyah_vm *ghvm)
 		goto err;
 	}
 
+	ret = gunyah_gmem_setup_demand_paging(ghvm);
+	if (ret) {
+		dev_warn(ghvm->parent,
+			 "Failed to set up gmem demand paging: %d\n", ret);
+		goto err;
+	}
+
+	ret = gunyah_rm_vm_set_address_layout(
+		ghvm->rm, ghvm->vmid, GUNYAH_RM_RANGE_ID_IMAGE,
+		ghvm->dtb.parcel_start << PAGE_SHIFT,
+		ghvm->dtb.parcel_pages << PAGE_SHIFT);
+	if (ret) {
+		dev_warn(ghvm->parent,
+			 "Failed to set location of DTB mem parcel: %d\n", ret);
+		goto err;
+	}
+
 	ret = gunyah_rm_vm_init(ghvm->rm, ghvm->vmid);
 	if (ret) {
 		ghvm->vm_status = GUNYAH_RM_VM_STATUS_INIT_FAILED;
diff --git a/drivers/virt/gunyah/vm_mgr.h b/drivers/virt/gunyah/vm_mgr.h
index 357414e67d72..088ed9c55376 100644
--- a/drivers/virt/gunyah/vm_mgr.h
+++ b/drivers/virt/gunyah/vm_mgr.h
@@ -98,4 +98,7 @@ int gunyah_gmem_reclaim_parcel(struct gunyah_vm *ghvm,
 			       struct gunyah_rm_mem_parcel *parcel, u64 gfn,
 			       u64 nr);
 
+int gunyah_gmem_setup_demand_paging(struct gunyah_vm *ghvm);
+int gunyah_gmem_demand_page(struct gunyah_vm *ghvm, u64 gpa, bool write);
+
 #endif
diff --git a/include/linux/gunyah.h b/include/linux/gunyah.h
index ae9be5eef7a9..ed461acb9e1b 100644
--- a/include/linux/gunyah.h
+++ b/include/linux/gunyah.h
@@ -223,6 +223,8 @@ struct gunyah_hypercall_vcpu_run_resp {
 			GUNYAH_VCPU_ADDRSPACE_VMMIO_READ	= 4,
 			/* VCPU has returned for MMIO WRITE */
 			GUNYAH_VCPU_ADDRSPACE_VMMIO_WRITE	= 5,
+			/* Host needs to satisfy a page fault */
+			GUNYAH_VCPU_ADDRSPACE_PAGE_FAULT	= 7,
 			/* clang-format on */
 		} state;
 		u64 sized_state;

-- 
2.43.0