git: 671a00491d7a - main - vm_iommu_map()/unmap(): stop transiently wiring already wired pages

The branch main has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=671a00491d7ac9d6663cdc597ff8c13024eda00d

commit 671a00491d7ac9d6663cdc597ff8c13024eda00d
Author:     Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2023-12-21 00:12:37 +0000
Commit:     Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2023-12-22 17:34:27 +0000

    vm_iommu_map()/unmap(): stop transiently wiring already wired pages
    
    Namely, switch from vm_fault_quick_hold() to pmap_extract() KPI to
    translate gpa to hpa. Assert that the looked up hpa belongs to the wired
    page, as it should be for the VM which is configured for pass-throu
    (this is theoretically a restriction that could be removed on newer
    DMARs).
    
    Noted by:       alc
    Reviewed by:    alc, jhb, markj
    Sponsored by:   The FreeBSD Foundation
    MFC after:      1 week
    Differential revision:  https://reviews.freebsd.org/D43140
---
 sys/amd64/vmm/vmm.c | 39 +++++++++++++++++++++++++--------------
 1 file changed, 25 insertions(+), 14 deletions(-)

diff --git a/sys/amd64/vmm/vmm.c b/sys/amd64/vmm/vmm.c
index 32ae9f9050a7..f399f876717d 100644
--- a/sys/amd64/vmm/vmm.c
+++ b/sys/amd64/vmm/vmm.c
@@ -1041,9 +1041,10 @@ vm_iommu_map(struct vm *vm)
 {
 	vm_paddr_t gpa, hpa;
 	struct mem_map *mm;
-	void *vp, *cookie;
 	int i;
 
+	sx_assert(&vm->mem_segs_lock, SX_LOCKED);
+
 	for (i = 0; i < VM_MAX_MEMMAPS; i++) {
 		mm = &vm->mem_maps[i];
 		if (!sysmem_mapping(vm, mm))
@@ -1057,13 +1058,24 @@ vm_iommu_map(struct vm *vm)
 		mm->flags |= VM_MEMMAP_F_IOMMU;
 
 		for (gpa = mm->gpa; gpa < mm->gpa + mm->len; gpa += PAGE_SIZE) {
-			vp = vm_gpa_hold_global(vm, gpa, PAGE_SIZE,
-			    VM_PROT_WRITE, &cookie);
-			KASSERT(vp != NULL, ("vm(%s) could not map gpa %#lx",
-			    vm_name(vm), gpa));
-			vm_gpa_release(cookie);
+			hpa = pmap_extract(vmspace_pmap(vm->vmspace), gpa);
+
+			/*
+			 * All mappings in the vmm vmspace must be
+			 * present since they are managed by vmm in this way.
+			 * Because we are in pass-through mode, the
+			 * mappings must also be wired.  This implies
+			 * that all pages must be mapped and wired,
+			 * allowing to use pmap_extract() and avoiding the
+			 * need to use vm_gpa_hold_global().
+			 *
+			 * This could change if/when we start
+			 * supporting page faults on IOMMU maps.
+			 */
+			KASSERT(vm_page_wired(PHYS_TO_VM_PAGE(hpa)),
+			    ("vm_iommu_map: vm %p gpa %jx hpa %jx not wired",
+			    vm, (uintmax_t)gpa, (uintmax_t)hpa));
 
-			hpa = DMAP_TO_PHYS((uintptr_t)vp);
 			iommu_create_mapping(vm->iommu, gpa, hpa, PAGE_SIZE);
 		}
 	}
@@ -1076,9 +1088,10 @@ vm_iommu_unmap(struct vm *vm)
 {
 	vm_paddr_t gpa;
 	struct mem_map *mm;
-	void *vp, *cookie;
 	int i;
 
+	sx_assert(&vm->mem_segs_lock, SX_LOCKED);
+
 	for (i = 0; i < VM_MAX_MEMMAPS; i++) {
 		mm = &vm->mem_maps[i];
 		if (!sysmem_mapping(vm, mm))
@@ -1092,12 +1105,10 @@ vm_iommu_unmap(struct vm *vm)
 		    mm->gpa, mm->len, mm->flags));
 
 		for (gpa = mm->gpa; gpa < mm->gpa + mm->len; gpa += PAGE_SIZE) {
-			vp = vm_gpa_hold_global(vm, gpa, PAGE_SIZE,
-			    VM_PROT_WRITE, &cookie);
-			KASSERT(vp != NULL, ("vm(%s) could not map gpa %#lx",
-			    vm_name(vm), gpa));
-			vm_gpa_release(cookie);
-
+			KASSERT(vm_page_wired(PHYS_TO_VM_PAGE(pmap_extract(
+			    vmspace_pmap(vm->vmspace), gpa))),
+			    ("vm_iommu_unmap: vm %p gpa %jx not wired",
+			    vm, (uintmax_t)gpa));
 			iommu_remove_mapping(vm->iommu, gpa, PAGE_SIZE);
 		}
 	}