vmm.c

/*
 * Copyright 2017 Red Hat Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */
#define NVKM_VMM_LEVELS_MAX 5
#include "vmm.h"

static void
nvkm_vmm_pt_del(struct nvkm_vmm_pt **ppgt)
{
	struct nvkm_vmm_pt *pgt = *ppgt;
	if (pgt) {
		kvfree(pgt->pde);
		kfree(pgt);
		*ppgt = NULL;
	}
}


static struct nvkm_vmm_pt *
nvkm_vmm_pt_new(const struct nvkm_vmm_desc *desc, bool sparse,
		const struct nvkm_vmm_page *page)
{
	const u32 pten = 1 << desc->bits;
	struct nvkm_vmm_pt *pgt;
	u32 lpte = 0;

	if (desc->type > PGT) {
		if (desc->type == SPT) {
			const struct nvkm_vmm_desc *pair = page[-1].desc;
			lpte = pten >> (desc->bits - pair->bits);
		} else {
			lpte = pten;
		}
	}

	if (!(pgt = kzalloc(sizeof(*pgt) + lpte, GFP_KERNEL)))
		return NULL;
	pgt->page = page ? page->shift : 0;
	pgt->sparse = sparse;

	if (desc->type == PGD) {
		pgt->pde = kvzalloc(sizeof(*pgt->pde) * pten, GFP_KERNEL);
		if (!pgt->pde) {
			kfree(pgt);
			return NULL;
		}
	}

	return pgt;
}

struct nvkm_vmm_iter {
	const struct nvkm_vmm_page *page;
	const struct nvkm_vmm_desc *desc;
	struct nvkm_vmm *vmm;
	u64 cnt;
	u16 max, lvl;
	u32 pte[NVKM_VMM_LEVELS_MAX];
	struct nvkm_vmm_pt *pt[NVKM_VMM_LEVELS_MAX];
	int flush;
};

#ifdef CONFIG_NOUVEAU_DEBUG_MMU
static const char *
nvkm_vmm_desc_type(const struct nvkm_vmm_desc *desc)
{
	switch (desc->type) {
	case PGD: return "PGD";
	case PGT: return "PGT";
	case SPT: return "SPT";
	case LPT: return "LPT";
	default:
		return "UNKNOWN";
	}
}

static void
nvkm_vmm_trace(struct nvkm_vmm_iter *it, char *buf)
{
	int lvl;
	for (lvl = it->max; lvl >= 0; lvl--) {
		if (lvl >= it->lvl)
			buf += sprintf(buf,  "%05x:", it->pte[lvl]);
		else
			buf += sprintf(buf, "xxxxx:");
	}
}

#define TRA(i,f,a...) do {                                                     \
	char _buf[NVKM_VMM_LEVELS_MAX * 7];                                    \
	struct nvkm_vmm_iter *_it = (i);                                       \
	nvkm_vmm_trace(_it, _buf);                                             \
	VMM_TRACE(_it->vmm, "%s "f, _buf, ##a);                                \
} while(0)
#else
#define TRA(i,f,a...)
#endif

static inline void
nvkm_vmm_flush_mark(struct nvkm_vmm_iter *it)
{
	it->flush = min(it->flush, it->max - it->lvl);
}

static inline void
nvkm_vmm_flush(struct nvkm_vmm_iter *it)
{
	if (it->flush != NVKM_VMM_LEVELS_MAX) {
		if (it->vmm->func->flush) {
			TRA(it, "flush: %d", it->flush);
			it->vmm->func->flush(it->vmm, it->flush);
		}
		it->flush = NVKM_VMM_LEVELS_MAX;
	}
}

static void
nvkm_vmm_unref_pdes(struct nvkm_vmm_iter *it)
{
	const struct nvkm_vmm_desc *desc = it->desc;
	const int type = desc[it->lvl].type == SPT;
	struct nvkm_vmm_pt *pgd = it->pt[it->lvl + 1];
	struct nvkm_vmm_pt *pgt = it->pt[it->lvl];
	struct nvkm_mmu_pt *pt = pgt->pt[type];
	struct nvkm_vmm *vmm = it->vmm;
	u32 pdei = it->pte[it->lvl + 1];

	/* Recurse up the tree, unreferencing/destroying unneeded PDs. */
	it->lvl++;
	if (--pgd->refs[0]) {
		const struct nvkm_vmm_desc_func *func = desc[it->lvl].func;
		/* PD has other valid PDEs, so we need a proper update. */
		TRA(it, "PDE unmap %s", nvkm_vmm_desc_type(&desc[it->lvl - 1]));
		pgt->pt[type] = NULL;
		if (!pgt->refs[!type]) {
			/* PDE no longer required. */
			if (pgd->pt[0]) {
				if (pgt->sparse) {
					func->sparse(vmm, pgd->pt[0], pdei, 1);
					pgd->pde[pdei] = NVKM_VMM_PDE_SPARSE;
				} else {
					func->unmap(vmm, pgd->pt[0], pdei, 1);
					pgd->pde[pdei] = NULL;
				}
			} else {
				/* Special handling for Tesla-class GPUs,
				 * where there's no central PD, but each
				 * instance has its own embedded PD.
				 */
				func->pde(vmm, pgd, pdei);
				pgd->pde[pdei] = NULL;
			}
		} else {
			/* PDE was pointing at dual-PTs and we're removing
			 * one of them, leaving the other in place.
			 */
			func->pde(vmm, pgd, pdei);
		}

		/* GPU may have cached the PTs, flush before freeing. */
		nvkm_vmm_flush_mark(it);
		nvkm_vmm_flush(it);
	} else {
		/* PD has no valid PDEs left, so we can just destroy it. */
		nvkm_vmm_unref_pdes(it);
	}

	/* Destroy PD/PT. */
	TRA(it, "PDE free %s", nvkm_vmm_desc_type(&desc[it->lvl - 1]));
	nvkm_mmu_ptc_put(vmm->mmu, vmm->bootstrapped, &pt);
	if (!pgt->refs[!type])
		nvkm_vmm_pt_del(&pgt);
	it->lvl--;
}

static void
nvkm_vmm_unref_sptes(struct nvkm_vmm_iter *it, struct nvkm_vmm_pt *pgt,
		     const struct nvkm_vmm_desc *desc, u32 ptei, u32 ptes)
{
	const struct nvkm_vmm_desc *pair = it->page[-1].desc;
	const u32 sptb = desc->bits - pair->bits;
	const u32 sptn = 1 << sptb;
	struct nvkm_vmm *vmm = it->vmm;
	u32 spti = ptei & (sptn - 1), lpti, pteb;

	/* Determine how many SPTEs are being touched under each LPTE,
	 * and drop reference counts.
	 */
	for (lpti = ptei >> sptb; ptes; spti = 0, lpti++) {
		const u32 pten = min(sptn - spti, ptes);
		pgt->pte[lpti] -= pten;
		ptes -= pten;
	}

	/* We're done here if there's no corresponding LPT. */
	if (!pgt->refs[0])
		return;

	for (ptei = pteb = ptei >> sptb; ptei < lpti; pteb = ptei) {
		/* Skip over any LPTEs that still have valid SPTEs. */
		if (pgt->pte[pteb] & NVKM_VMM_PTE_SPTES) {
			for (ptes = 1, ptei++; ptei < lpti; ptes++, ptei++) {
				if (!(pgt->pte[ptei] & NVKM_VMM_PTE_SPTES))
					break;
			}
			continue;
		}

		/* As there's no more non-UNMAPPED SPTEs left in the range
		 * covered by a number of LPTEs, the LPTEs once again take
		 * control over their address range.
		 *
		 * Determine how many LPTEs need to transition state.
		 */
		pgt->pte[ptei] &= ~NVKM_VMM_PTE_VALID;
		for (ptes = 1, ptei++; ptei < lpti; ptes++, ptei++) {
			if (pgt->pte[ptei] & NVKM_VMM_PTE_SPTES)
				break;
			pgt->pte[ptei] &= ~NVKM_VMM_PTE_VALID;
		}

		if (pgt->pte[pteb] & NVKM_VMM_PTE_SPARSE) {
			TRA(it, "LPTE %05x: U -> S %d PTEs", pteb, ptes);
			pair->func->sparse(vmm, pgt->pt[0], pteb, ptes);
		} else
		if (pair->func->invalid) {
			/* If the MMU supports it, restore the LPTE to the
			 * INVALID state to tell the MMU there is no point
			 * trying to fetch the corresponding SPTEs.
			 */
			TRA(it, "LPTE %05x: U -> I %d PTEs", pteb, ptes);
			pair->func->invalid(vmm, pgt->pt[0], pteb, ptes);
		}
	}
}

static bool
nvkm_vmm_unref_ptes(struct nvkm_vmm_iter *it, u32 ptei, u32 ptes)
{
	const struct nvkm_vmm_desc *desc = it->desc;
	const int type = desc->type == SPT;
	struct nvkm_vmm_pt *pgt = it->pt[0];

	/* Drop PTE references. */
	pgt->refs[type] -= ptes;

	/* Dual-PTs need special handling, unless PDE becoming invalid. */
	if (desc->type == SPT && (pgt->refs[0] || pgt->refs[1]))
		nvkm_vmm_unref_sptes(it, pgt, desc, ptei, ptes);

	/* PT no longer neeed?  Destroy it. */
	if (!pgt->refs[type]) {
		it->lvl++;
		TRA(it, "%s empty", nvkm_vmm_desc_type(desc));
		it->lvl--;
		nvkm_vmm_unref_pdes(it);
		return false; /* PTE writes for unmap() not necessary. */
	}

	return true;
}

static void
nvkm_vmm_ref_sptes(struct nvkm_vmm_iter *it, struct nvkm_vmm_pt *pgt,
		   const struct nvkm_vmm_desc *desc, u32 ptei, u32 ptes)
{
	const struct nvkm_vmm_desc *pair = it->page[-1].desc;
	const u32 sptb = desc->bits - pair->bits;
	const u32 sptn = 1 << sptb;
	struct nvkm_vmm *vmm = it->vmm;
	u32 spti = ptei & (sptn - 1), lpti, pteb;

	/* Determine how many SPTEs are being touched under each LPTE,
	 * and increase reference counts.
	 */
	for (lpti = ptei >> sptb; ptes; spti = 0, lpti++) {
		const u32 pten = min(sptn - spti, ptes);
		pgt->pte[lpti] += pten;
		ptes -= pten;
	}

	/* We're done here if there's no corresponding LPT. */
	if (!pgt->refs[0])
		return;

	for (ptei = pteb = ptei >> sptb; ptei < lpti; pteb = ptei) {
		/* Skip over any LPTEs that already have valid SPTEs. */
		if (pgt->pte[pteb] & NVKM_VMM_PTE_VALID) {
			for (ptes = 1, ptei++; ptei < lpti; ptes++, ptei++) {
				if (!(pgt->pte[ptei] & NVKM_VMM_PTE_VALID))
					break;
			}
			continue;
		}

		/* As there are now non-UNMAPPED SPTEs in the range covered
		 * by a number of LPTEs, we need to transfer control of the
		 * address range to the SPTEs.
		 *
		 * Determine how many LPTEs need to transition state.
		 */
		pgt->pte[ptei] |= NVKM_VMM_PTE_VALID;
		for (ptes = 1, ptei++; ptei < lpti; ptes++, ptei++) {
			if (pgt->pte[ptei] & NVKM_VMM_PTE_VALID)
				break;
			pgt->pte[ptei] |= NVKM_VMM_PTE_VALID;
		}

		if (pgt->pte[pteb] & NVKM_VMM_PTE_SPARSE) {
			const u32 spti = pteb * sptn;
			const u32 sptc = ptes * sptn;
			/* The entire LPTE is marked as sparse, we need
			 * to make sure that the SPTEs are too.
			 */
			TRA(it, "SPTE %05x: U -> S %d PTEs", spti, sptc);
			desc->func->sparse(vmm, pgt->pt[1], spti, sptc);
			/* Sparse LPTEs prevent SPTEs from being accessed. */
			TRA(it, "LPTE %05x: S -> U %d PTEs", pteb, ptes);
			pair->func->unmap(vmm, pgt->pt[0], pteb, ptes);
		} else
		if (pair->func->invalid) {
			/* MMU supports blocking SPTEs by marking an LPTE
			 * as INVALID.  We need to reverse that here.
			 */
			TRA(it, "LPTE %05x: I -> U %d PTEs", pteb, ptes);
			pair->func->unmap(vmm, pgt->pt[0], pteb, ptes);
		}
	}
}

static bool
nvkm_vmm_ref_ptes(struct nvkm_vmm_iter *it, u32 ptei, u32 ptes)
{
	const struct nvkm_vmm_desc *desc = it->desc;
	const int type = desc->type == SPT;
	struct nvkm_vmm_pt *pgt = it->pt[0];

	/* Take PTE references. */
	pgt->refs[type] += ptes;

	/* Dual-PTs need special handling. */
	if (desc->type == SPT)
		nvkm_vmm_ref_sptes(it, pgt, desc, ptei, ptes);

	return true;
}

static void
nvkm_vmm_sparse_ptes(const struct nvkm_vmm_desc *desc,
		     struct nvkm_vmm_pt *pgt, u32 ptei, u32 ptes)
{
	if (desc->type == PGD) {
		while (ptes--)
			pgt->pde[ptei++] = NVKM_VMM_PDE_SPARSE;
	} else
	if (desc->type == LPT) {
		memset(&pgt->pte[ptei], NVKM_VMM_PTE_SPARSE, ptes);
	}
}

static bool
nvkm_vmm_ref_hwpt(struct nvkm_vmm_iter *it, struct nvkm_vmm_pt *pgd, u32 pdei)
{
	const struct nvkm_vmm_desc *desc = &it->desc[it->lvl - 1];
	const int type = desc->type == SPT;
	struct nvkm_vmm_pt *pgt = pgd->pde[pdei];
	const bool zero = !pgt->sparse && !desc->func->invalid;
	struct nvkm_vmm *vmm = it->vmm;
	struct nvkm_mmu *mmu = vmm->mmu;
	struct nvkm_mmu_pt *pt;
	u32 pten = 1 << desc->bits;
	u32 pteb, ptei, ptes;
	u32 size = desc->size * pten;

	pgd->refs[0]++;

	pgt->pt[type] = nvkm_mmu_ptc_get(mmu, size, desc->align, zero);
	if (!pgt->pt[type]) {
		it->lvl--;
		nvkm_vmm_unref_pdes(it);
		return false;
	}

	if (zero)
		goto done;

	pt = pgt->pt[type];

	if (desc->type == LPT && pgt->refs[1]) {
		/* SPT already exists covering the same range as this LPT,
		 * which means we need to be careful that any LPTEs which
		 * overlap valid SPTEs are unmapped as opposed to invalid
		 * or sparse, which would prevent the MMU from looking at
		 * the SPTEs on some GPUs.
		 */
		for (ptei = pteb = 0; ptei < pten; pteb = ptei) {
			bool spte = pgt->pte[ptei] & NVKM_VMM_PTE_SPTES;
			for (ptes = 1, ptei++; ptei < pten; ptes++, ptei++) {
				bool next = pgt->pte[ptei] & NVKM_VMM_PTE_SPTES;
				if (spte != next)
					break;
			}

			if (!spte) {
				if (pgt->sparse)
					desc->func->sparse(vmm, pt, pteb, ptes);
				else
					desc->func->invalid(vmm, pt, pteb, ptes);
				memset(&pgt->pte[pteb], 0x00, ptes);
			} else {
				desc->func->unmap(vmm, pt, pteb, ptes);
				while (ptes--)
					pgt->pte[pteb++] |= NVKM_VMM_PTE_VALID;
			}
		}
	} else {
		if (pgt->sparse) {
			nvkm_vmm_sparse_ptes(desc, pgt, 0, pten);
			desc->func->sparse(vmm, pt, 0, pten);
		} else {
			desc->func->invalid(vmm, pt, 0, pten);
		}
	}

done:
	TRA(it, "PDE write %s", nvkm_vmm_desc_type(desc));
	it->desc[it->lvl].func->pde(it->vmm, pgd, pdei);
	nvkm_vmm_flush_mark(it);
	return true;
}

static bool
nvkm_vmm_ref_swpt(struct nvkm_vmm_iter *it, struct nvkm_vmm_pt *pgd, u32 pdei)
{
	const struct nvkm_vmm_desc *desc = &it->desc[it->lvl - 1];
	struct nvkm_vmm_pt *pgt = pgd->pde[pdei];

	pgt = nvkm_vmm_pt_new(desc, NVKM_VMM_PDE_SPARSED(pgt), it->page);
	if (!pgt) {
		if (!pgd->refs[0])
			nvkm_vmm_unref_pdes(it);
		return false;
	}

	pgd->pde[pdei] = pgt;
	return true;
}

static inline u64
nvkm_vmm_iter(struct nvkm_vmm *vmm, const struct nvkm_vmm_page *page,
	      u64 addr, u64 size, const char *name, bool ref,
	      bool (*REF_PTES)(struct nvkm_vmm_iter *, u32, u32),
	      nvkm_vmm_pte_func MAP_PTES, struct nvkm_vmm_map *map,
	      nvkm_vmm_pxe_func CLR_PTES)
{
	const struct nvkm_vmm_desc *desc = page->desc;
	struct nvkm_vmm_iter it;
	u64 bits = addr >> page->shift;

	it.page = page;
	it.desc = desc;
	it.vmm = vmm;
	it.cnt = size >> page->shift;
	it.flush = NVKM_VMM_LEVELS_MAX;

	/* Deconstruct address into PTE indices for each mapping level. */
	for (it.lvl = 0; desc[it.lvl].bits; it.lvl++) {
		it.pte[it.lvl] = bits & ((1 << desc[it.lvl].bits) - 1);
		bits >>= desc[it.lvl].bits;
	}
	it.max = --it.lvl;
	it.pt[it.max] = vmm->pd;

	it.lvl = 0;
	TRA(&it, "%s: %016llx %016llx %d %lld PTEs", name,
	         addr, size, page->shift, it.cnt);
	it.lvl = it.max;

	/* Depth-first traversal of page tables. */
	while (it.cnt) {
		struct nvkm_vmm_pt *pgt = it.pt[it.lvl];
		const int type = desc->type == SPT;
		const u32 pten = 1 << desc->bits;
		const u32 ptei = it.pte[0];
		const u32 ptes = min_t(u64, it.cnt, pten - ptei);

		/* Walk down the tree, finding page tables for each level. */
		for (; it.lvl; it.lvl--) {
			const u32 pdei = it.pte[it.lvl];
			struct nvkm_vmm_pt *pgd = pgt;

			/* Software PT. */
			if (ref && NVKM_VMM_PDE_INVALID(pgd->pde[pdei])) {
				if (!nvkm_vmm_ref_swpt(&it, pgd, pdei))
					goto fail;
			}
			it.pt[it.lvl - 1] = pgt = pgd->pde[pdei];

			/* Hardware PT.
			 *
			 * This is a separate step from above due to GF100 and
			 * newer having dual page tables at some levels, which
			 * are refcounted independently.
			 */
			if (ref && !pgt->refs[desc[it.lvl - 1].type == SPT]) {
				if (!nvkm_vmm_ref_hwpt(&it, pgd, pdei))
					goto fail;
			}
		}

		/* Handle PTE updates. */
		if (!REF_PTES || REF_PTES(&it, ptei, ptes)) {
			struct nvkm_mmu_pt *pt = pgt->pt[type];
			if (MAP_PTES || CLR_PTES) {
				if (MAP_PTES)
					MAP_PTES(vmm, pt, ptei, ptes, map);
				else
					CLR_PTES(vmm, pt, ptei, ptes);
				nvkm_vmm_flush_mark(&it);
			}
		}

		/* Walk back up the tree to the next position. */
		it.pte[it.lvl] += ptes;
		it.cnt -= ptes;
		if (it.cnt) {
			while (it.pte[it.lvl] == (1 << desc[it.lvl].bits)) {
				it.pte[it.lvl++] = 0;
				it.pte[it.lvl]++;
			}
		}
	};

	nvkm_vmm_flush(&it);
	return ~0ULL;

fail:
	/* Reconstruct the failure address so the caller is able to
	 * reverse any partially completed operations.
	 */
	addr = it.pte[it.max--];
	do {
		addr  = addr << desc[it.max].bits;
		addr |= it.pte[it.max];
	} while (it.max--);

	return addr << page->shift;
}

void
nvkm_vmm_ptes_unmap(struct nvkm_vmm *vmm, const struct nvkm_vmm_page *page,
		    u64 addr, u64 size, bool sparse)
{
	const struct nvkm_vmm_desc_func *func = page->desc->func;
	nvkm_vmm_iter(vmm, page, addr, size, "unmap", false, NULL, NULL, NULL,
		      sparse ? func->sparse : func->invalid ? func->invalid :
							      func->unmap);
}

void
nvkm_vmm_ptes_map(struct nvkm_vmm *vmm, const struct nvkm_vmm_page *page,
		  u64 addr, u64 size, struct nvkm_vmm_map *map,
		  nvkm_vmm_pte_func func)
{
	nvkm_vmm_iter(vmm, page, addr, size, "map", false,
		      NULL, func, map, NULL);
}

void
nvkm_vmm_ptes_put(struct nvkm_vmm *vmm, const struct nvkm_vmm_page *page,
		  u64 addr, u64 size)
{
	nvkm_vmm_iter(vmm, page, addr, size, "unref", false,
		      nvkm_vmm_unref_ptes, NULL, NULL, NULL);
}

int
nvkm_vmm_ptes_get(struct nvkm_vmm *vmm, const struct nvkm_vmm_page *page,
		  u64 addr, u64 size)
{
	u64 fail = nvkm_vmm_iter(vmm, page, addr, size, "ref", true,
				 nvkm_vmm_ref_ptes, NULL, NULL, NULL);
	if (fail != ~0ULL) {
		if (fail != addr)
			nvkm_vmm_ptes_put(vmm, page, addr, fail - addr);
		return -ENOMEM;
	}
	return 0;
}

void
nvkm_vmm_dtor(struct nvkm_vmm *vmm)
{
	if (vmm->bootstrapped) {
		const struct nvkm_vmm_page *page = vmm->func->page;
		const u64 limit = vmm->limit - vmm->start;

		while (page[1].shift)
			page++;

		nvkm_mmu_ptc_dump(vmm->mmu);
		nvkm_vmm_ptes_put(vmm, page, vmm->start, limit);
	}

	if (vmm->nullp) {
		dma_free_coherent(vmm->mmu->subdev.device->dev, 16 * 1024,
				  vmm->nullp, vmm->null);
	}

	if (vmm->pd) {
		nvkm_mmu_ptc_put(vmm->mmu, true, &vmm->pd->pt[0]);
		nvkm_vmm_pt_del(&vmm->pd);
	}
}

int
nvkm_vmm_ctor(const struct nvkm_vmm_func *func, struct nvkm_mmu *mmu,
	      u32 pd_header, u64 addr, u64 size, struct lock_class_key *key,
	      const char *name, struct nvkm_vmm *vmm)
{
	static struct lock_class_key _key;
	const struct nvkm_vmm_page *page = func->page;
	const struct nvkm_vmm_desc *desc;
	int levels, bits = 0;

	vmm->func = func;
	vmm->mmu = mmu;
	vmm->name = name;
	vmm->debug = mmu->subdev.debug;
	kref_init(&vmm->kref);

	__mutex_init(&vmm->mutex, "&vmm->mutex", key ? key : &_key);

	/* Locate the smallest page size supported by the backend, it will
	 * have the the deepest nesting of page tables.
	 */
	while (page[1].shift)
		page++;

	/* Locate the structure that describes the layout of the top-level
	 * page table, and determine the number of valid bits in a virtual
	 * address.
	 */
	for (levels = 0, desc = page->desc; desc->bits; desc++, levels++)
		bits += desc->bits;
	bits += page->shift;
	desc--;

	if (WARN_ON(levels > NVKM_VMM_LEVELS_MAX))
		return -EINVAL;

	vmm->start = addr;
	vmm->limit = size ? (addr + size) : (1ULL << bits);
	if (vmm->start > vmm->limit || vmm->limit > (1ULL << bits))
		return -EINVAL;

	/* Allocate top-level page table. */
	vmm->pd = nvkm_vmm_pt_new(desc, false, NULL);
	if (!vmm->pd)
		return -ENOMEM;
	vmm->pd->refs[0] = 1;
	INIT_LIST_HEAD(&vmm->join);

	/* ... and the GPU storage for it, except on Tesla-class GPUs that
	 * have the PD embedded in the instance structure.
	 */
	if (desc->size) {
		const u32 size = pd_header + desc->size * (1 << desc->bits);
		vmm->pd->pt[0] = nvkm_mmu_ptc_get(mmu, size, desc->align, true);
		if (!vmm->pd->pt[0])
			return -ENOMEM;
	}

	return 0;
}

int
nvkm_vmm_new_(const struct nvkm_vmm_func *func, struct nvkm_mmu *mmu,
	      u32 hdr, u64 addr, u64 size, struct lock_class_key *key,
	      const char *name, struct nvkm_vmm **pvmm)
{
	if (!(*pvmm = kzalloc(sizeof(**pvmm), GFP_KERNEL)))
		return -ENOMEM;
	return nvkm_vmm_ctor(func, mmu, hdr, addr, size, key, name, *pvmm);
}

static bool
nvkm_vmm_boot_ptes(struct nvkm_vmm_iter *it, u32 ptei, u32 ptes)
{
	const struct nvkm_vmm_desc *desc = it->desc;
	const int type = desc->type == SPT;
	nvkm_memory_boot(it->pt[0]->pt[type]->memory, it->vmm);
	return false;
}

int
nvkm_vmm_boot(struct nvkm_vmm *vmm)
{
	const struct nvkm_vmm_page *page = vmm->func->page;
	const u64 limit = vmm->limit - vmm->start;
	int ret;

	while (page[1].shift)
		page++;

	ret = nvkm_vmm_ptes_get(vmm, page, vmm->start, limit);
	if (ret)
		return ret;

	nvkm_vmm_iter(vmm, page, vmm->start, limit, "bootstrap", false,
		      nvkm_vmm_boot_ptes, NULL, NULL, NULL);
	vmm->bootstrapped = true;
	return 0;
}