> Date: Thu, 2 Sep 2021 22:16:52 +0200
> From: Martin Pieuchot <[email protected]>
>
> Diff below introduces two dummy pagers for subsystem that manipulate UVM
> objects that are 'special'. Those pagers will be used to enforce checks
> in functions that expect a lock to be held, like:
>
> KASSERT(obj == NULL || UVM_OBJ_IS_PMAP(obj) ||
> rw_write_held(obj->vmobjlock));
>
> They are also used, in the diff below, to document which routines expect
> such objects and a serialization offered by the KERNEL_LOCK(). More
> examples can be seen in my WIP unlocking diff.
>
> The idea is taken from NetBSD which also use such dummy pager for some
> of their pmaps. I don't believe there's a need to change anything with
> these usages of the uvm_obj_* API for the moment but at the same time it
> helps me to have such implicit documentation.
>
> ok?
And it follows a pattern that we already have.
I'm still not sure why the hell we need uvm objects in those pmaps,
but I'm also not too eager to delve into them to see if we can rid of
those bits right now.
ok kettenis@
> Index: arch/amd64/amd64/pmap.c
> ===================================================================
> RCS file: /cvs/src/sys/arch/amd64/amd64/pmap.c,v
> retrieving revision 1.145
> diff -u -p -r1.145 pmap.c
> --- arch/amd64/amd64/pmap.c 18 Jun 2021 06:17:28 -0000 1.145
> +++ arch/amd64/amd64/pmap.c 2 Sep 2021 19:55:57 -0000
> @@ -671,7 +671,7 @@ pmap_bootstrap(paddr_t first_avail, padd
>
> kpm = pmap_kernel();
> for (i = 0; i < PTP_LEVELS - 1; i++) {
> - uvm_obj_init(&kpm->pm_obj[i], NULL, 1);
> + uvm_obj_init(&kpm->pm_obj[i], &pmap_pager, 1);
> kpm->pm_ptphint[i] = NULL;
> }
> memset(&kpm->pm_list, 0, sizeof(kpm->pm_list)); /* pm_list not used */
> @@ -1307,7 +1307,7 @@ pmap_create(void)
>
> /* init uvm_object */
> for (i = 0; i < PTP_LEVELS - 1; i++) {
> - uvm_obj_init(&pmap->pm_obj[i], NULL, 1);
> + uvm_obj_init(&pmap->pm_obj[i], &pmap_pager, 1);
> pmap->pm_ptphint[i] = NULL;
> }
> pmap->pm_stats.wired_count = 0;
> Index: arch/hppa/hppa/pmap.c
> ===================================================================
> RCS file: /cvs/src/sys/arch/hppa/hppa/pmap.c,v
> retrieving revision 1.175
> diff -u -p -r1.175 pmap.c
> --- arch/hppa/hppa/pmap.c 16 Jun 2021 09:02:21 -0000 1.175
> +++ arch/hppa/hppa/pmap.c 2 Sep 2021 19:54:23 -0000
> @@ -496,7 +496,7 @@ pmap_bootstrap(vaddr_t vstart)
> */
> kpm = &kernel_pmap_store;
> bzero(kpm, sizeof(*kpm));
> - uvm_obj_init(&kpm->pm_obj, NULL, 1);
> + uvm_obj_init(&kpm->pm_obj, &pmap_pager, 1);
> kpm->pm_space = HPPA_SID_KERNEL;
> kpm->pm_pid = HPPA_PID_KERNEL;
> kpm->pm_pdir_pg = NULL;
> @@ -678,7 +678,7 @@ pmap_create(void)
>
> mtx_init(&pmap->pm_mtx, IPL_VM);
>
> - uvm_obj_init(&pmap->pm_obj, NULL, 1);
> + uvm_obj_init(&pmap->pm_obj, &pmap_pager, 1);
>
> for (space = 1 + arc4random_uniform(hppa_sid_max);
> pmap_sdir_get(space); space = (space + 1) % hppa_sid_max);
> Index: arch/i386/i386/pmap.c
> ===================================================================
> RCS file: /cvs/src/sys/arch/i386/i386/pmap.c,v
> retrieving revision 1.214
> diff -u -p -r1.214 pmap.c
> --- arch/i386/i386/pmap.c 16 Jun 2021 09:02:21 -0000 1.214
> +++ arch/i386/i386/pmap.c 2 Sep 2021 19:55:57 -0000
> @@ -963,7 +963,7 @@ pmap_bootstrap(vaddr_t kva_start)
> kpm = pmap_kernel();
> mtx_init(&kpm->pm_mtx, -1); /* must not be used */
> mtx_init(&kpm->pm_apte_mtx, IPL_VM);
> - uvm_obj_init(&kpm->pm_obj, NULL, 1);
> + uvm_obj_init(&kpm->pm_obj, &pmap_pager, 1);
> bzero(&kpm->pm_list, sizeof(kpm->pm_list)); /* pm_list not used */
> kpm->pm_pdir = (vaddr_t)(proc0.p_addr->u_pcb.pcb_cr3 + KERNBASE);
> kpm->pm_pdirpa = proc0.p_addr->u_pcb.pcb_cr3;
> @@ -1348,7 +1348,7 @@ pmap_create(void)
> mtx_init(&pmap->pm_apte_mtx, IPL_VM);
>
> /* init uvm_object */
> - uvm_obj_init(&pmap->pm_obj, NULL, 1);
> + uvm_obj_init(&pmap->pm_obj, &pmap_pager, 1);
> pmap->pm_stats.wired_count = 0;
> pmap->pm_stats.resident_count = 1; /* count the PDP allocd below */
> pmap->pm_ptphint = NULL;
> Index: uvm/uvm_object.c
> ===================================================================
> RCS file: /cvs/src/sys/uvm/uvm_object.c,v
> retrieving revision 1.19
> diff -u -p -r1.19 uvm_object.c
> --- uvm/uvm_object.c 16 Jun 2021 09:02:21 -0000 1.19
> +++ uvm/uvm_object.c 2 Sep 2021 20:00:03 -0000
> @@ -41,6 +41,16 @@
>
> #include <uvm/uvm.h>
>
> +/* Dummy object used by some pmaps for sanity checks. */
> +const struct uvm_pagerops pmap_pager = {
> + /* nothing */
> +};
> +
> +/* Dummy object used by the buffer cache for sanity checks. */
> +const struct uvm_pagerops bufcache_pager = {
> + /* nothing */
> +};
> +
> /* We will fetch this page count per step */
> #define FETCH_PAGECOUNT 16
>
> @@ -159,6 +169,9 @@ uvm_obj_free(struct uvm_object *uobj)
> {
> struct vm_page *pg;
> struct pglist pgl;
> +
> + KASSERT(UVM_OBJ_IS_BUFCACHE(uobj));
> + KERNEL_ASSERT_LOCKED();
>
> TAILQ_INIT(&pgl);
> /*
> Index: uvm/uvm_object.h
> ===================================================================
> RCS file: /cvs/src/sys/uvm/uvm_object.h,v
> retrieving revision 1.26
> diff -u -p -r1.26 uvm_object.h
> --- uvm/uvm_object.h 16 Jun 2021 09:02:21 -0000 1.26
> +++ uvm/uvm_object.h 2 Sep 2021 20:02:13 -0000
> @@ -74,6 +74,8 @@ struct uvm_object {
>
> extern const struct uvm_pagerops uvm_vnodeops;
> extern const struct uvm_pagerops uvm_deviceops;
> +extern const struct uvm_pagerops pmap_pager;
> +extern const struct uvm_pagerops bufcache_pager;
>
> /* For object trees */
> int uvm_pagecmp(const struct vm_page *, const struct vm_page *);
> @@ -91,6 +93,12 @@ RBT_PROTOTYPE(uvm_objtree, vm_page, objt
>
> #define UVM_OBJ_IS_AOBJ(uobj)
> \
> ((uobj)->pgops == &aobj_pager)
> +
> +#define UVM_OBJ_IS_PMAP(uobj)
> \
> + ((uobj)->pgops == &pmap_pager)
> +
> +#define UVM_OBJ_IS_BUFCACHE(uobj) \
> + ((uobj)->pgops == &bufcache_pager)
>
> void uvm_obj_init(struct uvm_object *, const struct uvm_pagerops *, int);
> int uvm_obj_wire(struct uvm_object *, voff_t, voff_t, struct pglist *);
> Index: uvm/uvm_page.c
> ===================================================================
> RCS file: /cvs/src/sys/uvm/uvm_page.c,v
> retrieving revision 1.157
> diff -u -p -r1.157 uvm_page.c
> --- uvm/uvm_page.c 21 Apr 2021 10:02:05 -0000 1.157
> +++ uvm/uvm_page.c 2 Sep 2021 19:59:22 -0000
> @@ -791,6 +791,8 @@ uvm_pagealloc_multi(struct uvm_object *o
> struct vm_page *pg;
> int i, r;
>
> + KASSERT(UVM_OBJ_IS_BUFCACHE(obj));
> + KERNEL_ASSERT_LOCKED();
>
> TAILQ_INIT(&plist);
> r = uvm_pglistalloc(size, dma_constraint.ucr_low,
> @@ -823,6 +825,8 @@ uvm_pagerealloc_multi(struct uvm_object
> int i, r;
> voff_t offset;
>
> + KASSERT(UVM_OBJ_IS_BUFCACHE(obj));
> + KERNEL_ASSERT_LOCKED();
>
> TAILQ_INIT(&plist);
> if (size == 0)
>
>
