kvm_paging_tmpl.h

/*
 * Kernel-based Virtual Machine driver for Linux
 *
 * This module enables machines with Intel VT-x extensions to run virtual
 * machines without emulation or binary translation.
 *
 * MMU support
 *
 * Copyright (C) 2006 Qumranet, Inc.
 *
 * Authors:
 *   Yaniv Kamay  <yaniv@qumranet.com>
 *   Avi Kivity   <avi@qumranet.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2.  See
 * the COPYING file in the top-level directory.
 *
 * Copyright 2011 Joyent, Inc. All rights reserved.
 */
#include <sys/sysmacros.h>
#include <sys/atomic.h>

/*
 * We need the mmu code to access both 32-bit and 64-bit guest ptes,
 * so the code in this file is compiled twice, once per pte size.
 */

#if PTTYPE == 64

#define	pt_element_t uint64_t
#define	guest_walker guest_walker64
#define	FNAME(name) paging##64_##name
#define	PT_BASE_ADDR_MASK PT64_BASE_ADDR_MASK
#define	PT_LVL_ADDR_MASK(lvl) PT64_LVL_ADDR_MASK(lvl)
#define	PT_LVL_OFFSET_MASK(lvl) PT64_LVL_OFFSET_MASK(lvl)
#define	PT_INDEX(addr, level) PT64_INDEX(addr, level)
#define	PT_LEVEL_MASK(level) PT64_LEVEL_MASK(level)
#define	PT_LEVEL_BITS PT64_LEVEL_BITS
#define	PT_MAX_FULL_LEVELS 4
#define	CMPXCHG atomic_cas_64

#elif PTTYPE == 32

#define	pt_element_t uint32_t
#define	guest_walker guest_walker32
#define	FNAME(name) paging##32_##name
#define	PT_BASE_ADDR_MASK PT32_BASE_ADDR_MASK
#define	PT_LVL_ADDR_MASK(lvl) PT32_LVL_ADDR_MASK(lvl)
#define	PT_LVL_OFFSET_MASK(lvl) PT32_LVL_OFFSET_MASK(lvl)
#define	PT_INDEX(addr, level) PT32_INDEX(addr, level)
#define	PT_LEVEL_MASK(level) PT32_LEVEL_MASK(level)
#define	PT_LEVEL_BITS PT32_LEVEL_BITS
#define	PT_MAX_FULL_LEVELS 2
#define	CMPXCHG atomic_cas_32

#else

#error Invalid PTTYPE value

#endif

#define	gpte_to_gfn_lvl		FNAME(gpte_to_gfn_lvl)
#define	gpte_to_gfn(pte)	gpte_to_gfn_lvl((pte), PT_PAGE_TABLE_LEVEL)

/*
 * The guest_walker structure emulates the behavior of the hardware page
 * table walker.
 */
struct guest_walker {
	int level;
	gfn_t table_gfn[PT_MAX_FULL_LEVELS];
	pt_element_t ptes[PT_MAX_FULL_LEVELS];
	gpa_t pte_gpa[PT_MAX_FULL_LEVELS];
	unsigned pt_access;
	unsigned pte_access;
	gfn_t gfn;
	uint32_t error_code;
};

static gfn_t gpte_to_gfn_lvl(pt_element_t gpte, int lvl)
{
	return ((gpte & PT_LVL_ADDR_MASK(lvl)) >> PAGESHIFT);
}

extern page_t *gfn_to_page(struct kvm *kvm, gfn_t gfn);

static int
FNAME(cmpxchg_gpte)(struct kvm *kvm, gfn_t table_gfn, unsigned index,
    pt_element_t orig_pte, pt_element_t new_pte)
{
	pt_element_t ret;
	pt_element_t *table;
	page_t *page;

	page = gfn_to_page(kvm, table_gfn);

	table = (pt_element_t *)page_address(page);
	ret = CMPXCHG(&table[index], orig_pte, new_pte);
	kvm_release_page_dirty(page);

	return (ret != orig_pte);
}

static unsigned FNAME(gpte_access)(struct kvm_vcpu *vcpu, pt_element_t gpte)
{
	unsigned access;

	access = (gpte & (PT_WRITABLE_MASK | PT_USER_MASK)) | ACC_EXEC_MASK;
#if PTTYPE == 64
	if (is_nx(vcpu))
		access &= ~(gpte >> PT64_NX_SHIFT);
#endif
	return (access);
}

extern int is_cpuid_PSE36(void);
extern int is_present_gpte(unsigned long pte);
extern int is_dirty_gpte(unsigned long pte);
extern gfn_t pse36_gfn_delta(uint32_t gpte);
extern void __set_spte(uint64_t *sptep, uint64_t spte);
extern gpa_t gfn_to_gpa(gfn_t gfn);

/*
 * Fetch a guest pte for a guest virtual address
 */
static int
FNAME(walk_addr)(struct guest_walker *walker, struct kvm_vcpu *vcpu,
    gva_t addr, int write_fault, int user_fault, int fetch_fault)
{
	pt_element_t pte;
	gfn_t table_gfn;
	unsigned index, pt_access, pte_access;
	gpa_t pte_gpa;
	int rsvd_fault = 0;

walk:
	walker->level = vcpu->arch.mmu.root_level;
	pte = vcpu->arch.cr3;
#if PTTYPE == 64
	if (!is_long_mode(vcpu)) {
		pte = kvm_pdptr_read(vcpu, (addr >> 30) & 3);

		if (!is_present_gpte(pte))
			goto not_present;
		--walker->level;
	}
#endif

	pt_access = ACC_ALL;

	for (;;) {
		index = PT_INDEX(addr, walker->level);

		table_gfn = gpte_to_gfn(pte);
		pte_gpa = gfn_to_gpa(table_gfn);
		pte_gpa += index * sizeof (pt_element_t);
		walker->table_gfn[walker->level - 1] = table_gfn;
		walker->pte_gpa[walker->level - 1] = pte_gpa;

		if (kvm_read_guest(vcpu->kvm, pte_gpa, &pte, sizeof (pte)))
			goto not_present;

		if (!is_present_gpte(pte))
			goto not_present;

		rsvd_fault = is_rsvd_bits_set(vcpu, pte, walker->level);
		if (rsvd_fault)
			goto access_error;

		if (write_fault && !is_writable_pte(pte))
			if (user_fault || is_write_protection(vcpu))
				goto access_error;

		if (user_fault && !(pte & PT_USER_MASK))
			goto access_error;

#if PTTYPE == 64
		if (fetch_fault && is_nx(vcpu) && (pte & PT64_NX_MASK))
			goto access_error;
#endif

		if (!(pte & PT_ACCESSED_MASK)) {
			mark_page_dirty(vcpu->kvm, table_gfn);
			if (FNAME(cmpxchg_gpte)(vcpu->kvm, table_gfn,
			    index, pte, pte|PT_ACCESSED_MASK))
				goto walk;
			pte |= PT_ACCESSED_MASK;
		}

		pte_access = pt_access & FNAME(gpte_access)(vcpu, pte);

		walker->ptes[walker->level - 1] = pte;

		if ((walker->level == PT_PAGE_TABLE_LEVEL) ||
		    ((walker->level == PT_DIRECTORY_LEVEL) &&
				(pte & PT_PAGE_SIZE_MASK) &&
				(PTTYPE == 64 || is_pse(vcpu))) ||
		    ((walker->level == PT_PDPE_LEVEL) &&
				(pte & PT_PAGE_SIZE_MASK) &&
				is_long_mode(vcpu))) {
			int lvl = walker->level;

			walker->gfn = gpte_to_gfn_lvl(pte, lvl);
			walker->gfn += (addr & PT_LVL_OFFSET_MASK(lvl))
					>> PAGESHIFT;

			if (PTTYPE == 32 &&
			    walker->level == PT_DIRECTORY_LEVEL &&
			    is_cpuid_PSE36())
				walker->gfn += pse36_gfn_delta(pte);

			break;
		}

		pt_access = pte_access;
		--walker->level;
	}

	if (write_fault && !is_dirty_gpte(pte)) {
		int ret;

		mark_page_dirty(vcpu->kvm, table_gfn);
		ret = FNAME(cmpxchg_gpte)(vcpu->kvm, table_gfn, index, pte,
			    pte|PT_DIRTY_MASK);
		if (ret)
			goto walk;
		pte |= PT_DIRTY_MASK;
		walker->ptes[walker->level - 1] = pte;
	}

	walker->pt_access = pt_access;
	walker->pte_access = pte_access;
	return (1);

not_present:
	walker->error_code = 0;
	goto err;

access_error:
	walker->error_code = PFERR_PRESENT_MASK;

err:
	if (write_fault)
		walker->error_code |= PFERR_WRITE_MASK;
	if (user_fault)
		walker->error_code |= PFERR_USER_MASK;
	if (fetch_fault)
		walker->error_code |= PFERR_FETCH_MASK;
	if (rsvd_fault)
		walker->error_code |= PFERR_RSVD_MASK;

	return (0);
}

static void
FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *page,
    uint64_t *spte, const void *pte)
{
	pt_element_t gpte;
	unsigned pte_access;
	pfn_t pfn;

	gpte = *(const pt_element_t *)pte;
	if (~gpte & (PT_PRESENT_MASK | PT_ACCESSED_MASK)) {
		if (!is_present_gpte(gpte))
			__set_spte(spte, shadow_notrap_nonpresent_pte);
		return;
	}
	pte_access = page->role.access & FNAME(gpte_access)(vcpu, gpte);
	if (gpte_to_gfn(gpte) != vcpu->arch.update_pte.gfn)
		return;

	pfn = vcpu->arch.update_pte.pfn;
	if (is_error_pfn(pfn))
		return;

	kvm_get_pfn(vcpu, pfn);
	/*
	 * we call mmu_set_spte() with reset_host_protection = 1 beacuse that
	 * vcpu->arch.update_pte.pfn was fetched from get_user_pages(write = 1).
	 */
	mmu_set_spte(vcpu, spte, page->role.access, pte_access, 0, 0,
	    gpte & PT_DIRTY_MASK, NULL, PT_PAGE_TABLE_LEVEL,
	    gpte_to_gfn(gpte), pfn, 1, 1);
}

/*
 * Fetch a shadow pte for a specific level in the paging hierarchy.
 */
static uint64_t *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
    struct guest_walker *gw, int user_fault, int write_fault, int hlevel,
    int *ptwrite, pfn_t pfn)
{
	unsigned access = gw->pt_access;
	struct kvm_mmu_page *shadow_page;
	uint64_t spte, *sptep = NULL;
	int direct;
	gfn_t table_gfn;
	int r;
	int level;
	pt_element_t curr_pte;
	struct kvm_shadow_walk_iterator iterator;

	if (!is_present_gpte(gw->ptes[gw->level - 1]))
		return (NULL);

	for_each_shadow_entry(vcpu, addr, iterator) {
		level = iterator.level;
		sptep = iterator.sptep;
		if (iterator.level == hlevel) {
			mmu_set_spte(vcpu, sptep, access,
			    gw->pte_access & access, user_fault, write_fault,
			    gw->ptes[gw->level-1] & PT_DIRTY_MASK, ptwrite,
			    level, gw->gfn, pfn, 0, 1);
			break;
		}

		if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep)) {
			struct kvm_mmu_page *child;
			unsigned direct_access;

			if (level != gw->level)
				continue;

			/*
			 * For the direct sp, if the guest pte's dirty bit
			 * changed form clean to dirty, it will corrupt the
			 * sp's access: allow writable in the read-only sp,
			 * so we should update the spte at this point to get
			 * a new sp with the correct access.
			 */
			direct_access = gw->pt_access & gw->pte_access;
			if (!is_dirty_gpte(gw->ptes[gw->level - 1]))
				direct_access &= ~ACC_WRITE_MASK;

			child = page_header(vcpu->kvm,
			    *sptep & PT64_BASE_ADDR_MASK);

			if (child->role.access == direct_access)
				continue;

			mmu_page_remove_parent_pte(child, sptep);
			__set_spte(sptep, shadow_trap_nonpresent_pte);
			kvm_flush_remote_tlbs(vcpu->kvm);
		}

		if (is_large_pte(*sptep)) {
			rmap_remove(vcpu->kvm, sptep);
			__set_spte(sptep, shadow_trap_nonpresent_pte);
			kvm_flush_remote_tlbs(vcpu->kvm);
		}

		if (level <= gw->level) {
			int delta = level - gw->level + 1;
			direct = 1;
			if (!is_dirty_gpte(gw->ptes[level - delta]))
				access &= ~ACC_WRITE_MASK;
			access &= gw->pte_access;

			table_gfn = gpte_to_gfn(gw->ptes[level - delta]);
			/* advance table_gfn when emulating 1gb pages with 4k */
			if (delta == 0)
				table_gfn += PT_INDEX(addr, level);
		} else {
			direct = 0;
			table_gfn = gw->table_gfn[level - 2];
		}
		shadow_page = kvm_mmu_get_page(vcpu, table_gfn, addr, level-1,
		    direct, access, sptep);
		if (!direct) {
			r = kvm_read_guest_atomic(vcpu->kvm,
			    gw->pte_gpa[level - 2],
			    &curr_pte, sizeof (curr_pte));
			if (r || curr_pte != gw->ptes[level - 2]) {
				kvm_mmu_put_page(shadow_page, sptep);
				kvm_release_pfn_clean(pfn);
				sptep = NULL;
				break;
			}
		}

		spte = kvm_va2pa((caddr_t)shadow_page->spt)
			| PT_PRESENT_MASK | PT_ACCESSED_MASK
			| PT_WRITABLE_MASK | PT_USER_MASK;
		*sptep = spte;
	}

	return (sptep);
}

extern void kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu);

/*
 * Page fault handler.  There are several causes for a page fault:
 *   - there is no shadow pte for the guest pte
 *   - write access through a shadow pte marked read only so that we can set
 *     the dirty bit
 *   - write access to a shadow pte marked read only so we can update the page
 *     dirty bitmap, when userspace requests it
 *   - mmio access; in this case we will never install a present shadow pte
 *   - normal guest page fault due to the guest pte marked not present, not
 *     writable, or not executable
 *
 *  Returns: 1 if we need to emulate the instruction, 0 otherwise, or
 *           a negative value on error.
 */
static int
FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
    uint32_t error_code)
{
	int write_fault = error_code & PFERR_WRITE_MASK;
	int user_fault = error_code & PFERR_USER_MASK;
	int fetch_fault = error_code & PFERR_FETCH_MASK;
	struct guest_walker walker;
	uint64_t *sptep;
	int write_pt = 0;
	int r;
	pfn_t pfn;
	int level = PT_PAGE_TABLE_LEVEL;
	unsigned long mmu_seq;

	r = mmu_topup_memory_caches(vcpu);
	if (r)
		return (r);

	/*
	 * Look up the guest pte for the faulting address.
	 */
	r = FNAME(walk_addr)(&walker, vcpu, addr, write_fault, user_fault,
	    fetch_fault);

	/*
	 * The page is not mapped by the guest.  Let the guest handle it.
	 */
	if (!r) {
		inject_page_fault(vcpu, addr, walker.error_code);
		vcpu->arch.last_pt_write_count = 0; /* reset fork detector */
		return (0);
	}

	if (walker.level >= PT_DIRECTORY_LEVEL) {
		level = MIN(walker.level, mapping_level(vcpu, walker.gfn));
		walker.gfn = walker.gfn & ~(KVM_PAGES_PER_HPAGE(level) - 1);
	}
	smp_rmb();
	pfn = gfn_to_pfn(vcpu->kvm, walker.gfn);

	/* mmio */
	if (is_error_pfn(pfn)) {
		kvm_release_pfn_clean(pfn);
		return (1);
	}

	mutex_enter(&vcpu->kvm->mmu_lock);
	kvm_mmu_free_some_pages(vcpu);
	sptep = FNAME(fetch)(vcpu, addr, &walker, user_fault, write_fault,
	    level, &write_pt, pfn);

	if (!write_pt)
		vcpu->arch.last_pt_write_count = 0; /* reset fork detector */

	mutex_exit(&vcpu->kvm->mmu_lock);

	return (write_pt);

out_unlock:
	mutex_exit(&vcpu->kvm->mmu_lock);
	kvm_release_pfn_clean(pfn);
	return (0);
}

static void
FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)
{
	struct kvm_shadow_walk_iterator iterator;
	int level;
	uint64_t *sptep;
	int need_flush = 0;

	mutex_enter(&vcpu->kvm->mmu_lock);

	for_each_shadow_entry(vcpu, gva, iterator) {
		level = iterator.level;
		sptep = iterator.sptep;

		if (level == PT_PAGE_TABLE_LEVEL ||
		    ((level == PT_DIRECTORY_LEVEL && is_large_pte(*sptep))) ||
		    ((level == PT_PDPE_LEVEL && is_large_pte(*sptep)))) {

			if (is_shadow_present_pte(*sptep)) {
				rmap_remove(vcpu->kvm, sptep);
				need_flush = 1;
			}
			__set_spte(sptep, shadow_trap_nonpresent_pte);
			break;
		}

		if (!is_shadow_present_pte(*sptep))
			break;
	}

	if (need_flush)
		kvm_flush_remote_tlbs(vcpu->kvm);
	mutex_exit(&vcpu->kvm->mmu_lock);
}

static gpa_t
FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t vaddr, uint32_t access,
    uint32_t *error)
{
	struct guest_walker walker;
	gpa_t gpa = UNMAPPED_GVA;
	int r;

	r = FNAME(walk_addr)(&walker, vcpu, vaddr,
	    !!(access & PFERR_WRITE_MASK),
	    !!(access & PFERR_USER_MASK),
	    !!(access & PFERR_FETCH_MASK));

	if (r) {
		gpa = gfn_to_gpa(walker.gfn);
		gpa |= vaddr & ~PAGEMASK;
	} else if (error)
		*error = walker.error_code;

	return (gpa);
}

static void
FNAME(prefetch_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
{
	int i, j, offset, r;
	pt_element_t pt[256 / sizeof (pt_element_t)];
	gpa_t pte_gpa;

	if (sp->role.direct ||
	    (PTTYPE == 32 && sp->role.level > PT_PAGE_TABLE_LEVEL)) {
		nonpaging_prefetch_page(vcpu, sp);
		return;
	}

	pte_gpa = gfn_to_gpa(sp->gfn);
	if (PTTYPE == 32) {
		offset = sp->role.quadrant << PT64_LEVEL_BITS;
		pte_gpa += offset * sizeof (pt_element_t);
	}

	for (i = 0; i < PT64_ENT_PER_PAGE; i += ARRAY_SIZE(pt)) {
		r = kvm_read_guest_atomic(vcpu->kvm, pte_gpa, pt, sizeof (pt));
		pte_gpa += ARRAY_SIZE(pt) * sizeof (pt_element_t);
		for (j = 0; j < ARRAY_SIZE(pt); ++j)
			if (r || is_present_gpte(pt[j]))
				sp->spt[i+j] = shadow_trap_nonpresent_pte;
			else
				sp->spt[i+j] = shadow_notrap_nonpresent_pte;
	}
}

/*
 * Using the cached information from sp->gfns is safe because:
 * - The spte has a reference to the struct page, so the pfn for a given gfn
 *   can't change unless all sptes pointing to it are nuked first.
 * - Alias changes zap the entire shadow cache.
 */
static int
FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
{
	int i, offset, nr_present;
	int reset_host_protection;

	offset = nr_present = 0;

	if (PTTYPE == 32)
		offset = sp->role.quadrant << PT64_LEVEL_BITS;

	for (i = 0; i < PT64_ENT_PER_PAGE; i++) {
		unsigned pte_access;
		pt_element_t gpte;
		gpa_t pte_gpa;
		gfn_t gfn = sp->gfns[i];

		if (!is_shadow_present_pte(sp->spt[i]))
			continue;

		pte_gpa = gfn_to_gpa(sp->gfn);
		pte_gpa += (i+offset) * sizeof (pt_element_t);

		if (kvm_read_guest_atomic(vcpu->kvm, pte_gpa, &gpte,
		    sizeof (pt_element_t)))
			return (-EINVAL);

		if (gpte_to_gfn(gpte) != gfn || !is_present_gpte(gpte) ||
		    !(gpte & PT_ACCESSED_MASK)) {
			uint64_t nonpresent;

			rmap_remove(vcpu->kvm, &sp->spt[i]);
			if (is_present_gpte(gpte))
				nonpresent = shadow_trap_nonpresent_pte;
			else
				nonpresent = shadow_notrap_nonpresent_pte;
			__set_spte(&sp->spt[i], nonpresent);
			continue;
		}

		nr_present++;
		pte_access = sp->role.access & FNAME(gpte_access)(vcpu, gpte);
		if (!(sp->spt[i] & SPTE_HOST_WRITEABLE)) {
			pte_access &= ~ACC_WRITE_MASK;
			reset_host_protection = 0;
		} else {
			reset_host_protection = 1;
		}
		set_spte(vcpu, &sp->spt[i], pte_access, 0, 0,
		    is_dirty_gpte(gpte), PT_PAGE_TABLE_LEVEL, gfn,
		    spte_to_pfn(sp->spt[i]), 1, 0, reset_host_protection);
	}

	return (!nr_present);
}

#undef pt_element_t
#undef guest_walker
#undef FNAME
#undef PT_BASE_ADDR_MASK
#undef PT_INDEX
#undef PT_LEVEL_MASK
#undef PT_LVL_ADDR_MASK
#undef PT_LVL_OFFSET_MASK
#undef PT_LEVEL_BITS
#undef PT_MAX_FULL_LEVELS
#undef gpte_to_gfn
#undef gpte_to_gfn_lvl
#undef CMPXCHG