mmu.c

/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * KVM/MIPS MMU handling in the KVM module.
 *
 * Copyright (C) 2012  MIPS Technologies, Inc.  All rights reserved.
 * Authors: Sanjay Lal <sanjayl@kymasys.com>
 */

#include <linux/highmem.h>
#include <linux/kvm_host.h>
#include <linux/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/pgalloc.h>

/*
 * KVM_MMU_CACHE_MIN_PAGES is the number of GPA page table translation levels
 * for which pages need to be cached.
 */
#if defined(__PAGETABLE_PMD_FOLDED)
#define KVM_MMU_CACHE_MIN_PAGES 1
#else
#define KVM_MMU_CACHE_MIN_PAGES 2
#endif

static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
				  int min, int max)
{
	void *page;

	BUG_ON(max > KVM_NR_MEM_OBJS);
	if (cache->nobjs >= min)
		return 0;
	while (cache->nobjs < max) {
		page = (void *)__get_free_page(GFP_KERNEL);
		if (!page)
			return -ENOMEM;
		cache->objects[cache->nobjs++] = page;
	}
	return 0;
}

static void mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc)
{
	while (mc->nobjs)
		free_page((unsigned long)mc->objects[--mc->nobjs]);
}

static void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc)
{
	void *p;

	BUG_ON(!mc || !mc->nobjs);
	p = mc->objects[--mc->nobjs];
	return p;
}

void kvm_mmu_free_memory_caches(struct kvm_vcpu *vcpu)
{
	mmu_free_memory_cache(&vcpu->arch.mmu_page_cache);
}

/**
 * kvm_mips_walk_pgd() - Walk page table with optional allocation.
 * @pgd:	Page directory pointer.
 * @addr:	Address to index page table using.
 * @cache:	MMU page cache to allocate new page tables from, or NULL.
 *
 * Walk the page tables pointed to by @pgd to find the PTE corresponding to the
 * address @addr. If page tables don't exist for @addr, they will be created
 * from the MMU cache if @cache is not NULL.
 *
 * Returns:	Pointer to pte_t corresponding to @addr.
 *		NULL if a page table doesn't exist for @addr and !@cache.
 *		NULL if a page table allocation failed.
 */
static pte_t *kvm_mips_walk_pgd(pgd_t *pgd, struct kvm_mmu_memory_cache *cache,
				unsigned long addr)
{
	pud_t *pud;
	pmd_t *pmd;

	pgd += pgd_index(addr);
	if (pgd_none(*pgd)) {
		/* Not used on MIPS yet */
		BUG();
		return NULL;
	}
	pud = pud_offset(pgd, addr);
	if (pud_none(*pud)) {
		pmd_t *new_pmd;

		if (!cache)
			return NULL;
		new_pmd = mmu_memory_cache_alloc(cache);
		pmd_init((unsigned long)new_pmd,
			 (unsigned long)invalid_pte_table);
		pud_populate(NULL, pud, new_pmd);
	}
	pmd = pmd_offset(pud, addr);
	if (pmd_none(*pmd)) {
		pte_t *new_pte;

		if (!cache)
			return NULL;
		new_pte = mmu_memory_cache_alloc(cache);
		clear_page(new_pte);
		pmd_populate_kernel(NULL, pmd, new_pte);
	}
	return pte_offset(pmd, addr);
}

static int kvm_mips_map_page(struct kvm *kvm, gfn_t gfn)
{
	int srcu_idx, err = 0;
	kvm_pfn_t pfn;

	if (kvm->arch.guest_pmap[gfn] != KVM_INVALID_PAGE)
		return 0;

	srcu_idx = srcu_read_lock(&kvm->srcu);
	pfn = gfn_to_pfn(kvm, gfn);

	if (is_error_noslot_pfn(pfn)) {
		kvm_err("Couldn't get pfn for gfn %#llx!\n", gfn);
		err = -EFAULT;
		goto out;
	}

	kvm->arch.guest_pmap[gfn] = pfn;
out:
	srcu_read_unlock(&kvm->srcu, srcu_idx);
	return err;
}

static pte_t *kvm_trap_emul_pte_for_gva(struct kvm_vcpu *vcpu,
					unsigned long addr)
{
	struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache;
	pgd_t *pgdp;
	int ret;

	/* We need a minimum of cached pages ready for page table creation */
	ret = mmu_topup_memory_cache(memcache, KVM_MMU_CACHE_MIN_PAGES,
				     KVM_NR_MEM_OBJS);
	if (ret)
		return NULL;

	if (KVM_GUEST_KERNEL_MODE(vcpu))
		pgdp = vcpu->arch.guest_kernel_mm.pgd;
	else
		pgdp = vcpu->arch.guest_user_mm.pgd;

	return kvm_mips_walk_pgd(pgdp, memcache, addr);
}

void kvm_trap_emul_invalidate_gva(struct kvm_vcpu *vcpu, unsigned long addr,
				  bool user)
{
	pgd_t *pgdp;
	pte_t *ptep;

	addr &= PAGE_MASK << 1;

	pgdp = vcpu->arch.guest_kernel_mm.pgd;
	ptep = kvm_mips_walk_pgd(pgdp, NULL, addr);
	if (ptep) {
		ptep[0] = pfn_pte(0, __pgprot(0));
		ptep[1] = pfn_pte(0, __pgprot(0));
	}

	if (user) {
		pgdp = vcpu->arch.guest_user_mm.pgd;
		ptep = kvm_mips_walk_pgd(pgdp, NULL, addr);
		if (ptep) {
			ptep[0] = pfn_pte(0, __pgprot(0));
			ptep[1] = pfn_pte(0, __pgprot(0));
		}
	}
}

/*
 * kvm_mips_flush_gva_{pte,pmd,pud,pgd,pt}.
 * Flush a range of guest physical address space from the VM's GPA page tables.
 */

static bool kvm_mips_flush_gva_pte(pte_t *pte, unsigned long start_gva,
				   unsigned long end_gva)
{
	int i_min = __pte_offset(start_gva);
	int i_max = __pte_offset(end_gva);
	bool safe_to_remove = (i_min == 0 && i_max == PTRS_PER_PTE - 1);
	int i;

	/*
	 * There's no freeing to do, so there's no point clearing individual
	 * entries unless only part of the last level page table needs flushing.
	 */
	if (safe_to_remove)
		return true;

	for (i = i_min; i <= i_max; ++i) {
		if (!pte_present(pte[i]))
			continue;

		set_pte(pte + i, __pte(0));
	}
	return false;
}

static bool kvm_mips_flush_gva_pmd(pmd_t *pmd, unsigned long start_gva,
				   unsigned long end_gva)
{
	pte_t *pte;
	unsigned long end = ~0ul;
	int i_min = __pmd_offset(start_gva);
	int i_max = __pmd_offset(end_gva);
	bool safe_to_remove = (i_min == 0 && i_max == PTRS_PER_PMD - 1);
	int i;

	for (i = i_min; i <= i_max; ++i, start_gva = 0) {
		if (!pmd_present(pmd[i]))
			continue;

		pte = pte_offset(pmd + i, 0);
		if (i == i_max)
			end = end_gva;

		if (kvm_mips_flush_gva_pte(pte, start_gva, end)) {
			pmd_clear(pmd + i);
			pte_free_kernel(NULL, pte);
		} else {
			safe_to_remove = false;
		}
	}
	return safe_to_remove;
}

static bool kvm_mips_flush_gva_pud(pud_t *pud, unsigned long start_gva,
				   unsigned long end_gva)
{
	pmd_t *pmd;
	unsigned long end = ~0ul;
	int i_min = __pud_offset(start_gva);
	int i_max = __pud_offset(end_gva);
	bool safe_to_remove = (i_min == 0 && i_max == PTRS_PER_PUD - 1);
	int i;

	for (i = i_min; i <= i_max; ++i, start_gva = 0) {
		if (!pud_present(pud[i]))
			continue;

		pmd = pmd_offset(pud + i, 0);
		if (i == i_max)
			end = end_gva;

		if (kvm_mips_flush_gva_pmd(pmd, start_gva, end)) {
			pud_clear(pud + i);
			pmd_free(NULL, pmd);
		} else {
			safe_to_remove = false;
		}
	}
	return safe_to_remove;
}

static bool kvm_mips_flush_gva_pgd(pgd_t *pgd, unsigned long start_gva,
				   unsigned long end_gva)
{
	pud_t *pud;
	unsigned long end = ~0ul;
	int i_min = pgd_index(start_gva);
	int i_max = pgd_index(end_gva);
	bool safe_to_remove = (i_min == 0 && i_max == PTRS_PER_PGD - 1);
	int i;

	for (i = i_min; i <= i_max; ++i, start_gva = 0) {
		if (!pgd_present(pgd[i]))
			continue;

		pud = pud_offset(pgd + i, 0);
		if (i == i_max)
			end = end_gva;

		if (kvm_mips_flush_gva_pud(pud, start_gva, end)) {
			pgd_clear(pgd + i);
			pud_free(NULL, pud);
		} else {
			safe_to_remove = false;
		}
	}
	return safe_to_remove;
}

void kvm_mips_flush_gva_pt(pgd_t *pgd, enum kvm_mips_flush flags)
{
	if (flags & KMF_GPA) {
		/* all of guest virtual address space could be affected */
		if (flags & KMF_KERN)
			/* useg, kseg0, seg2/3 */
			kvm_mips_flush_gva_pgd(pgd, 0, 0x7fffffff);
		else
			/* useg */
			kvm_mips_flush_gva_pgd(pgd, 0, 0x3fffffff);
	} else {
		/* useg */
		kvm_mips_flush_gva_pgd(pgd, 0, 0x3fffffff);

		/* kseg2/3 */
		if (flags & KMF_KERN)
			kvm_mips_flush_gva_pgd(pgd, 0x60000000, 0x7fffffff);
	}
}

/* XXXKYMA: Must be called with interrupts disabled */
int kvm_mips_handle_kseg0_tlb_fault(unsigned long badvaddr,
				    struct kvm_vcpu *vcpu)
{
	gfn_t gfn;
	kvm_pfn_t pfn0, pfn1;
	unsigned long vaddr = 0;
	struct kvm *kvm = vcpu->kvm;
	pte_t *ptep_gva;

	if (KVM_GUEST_KSEGX(badvaddr) != KVM_GUEST_KSEG0) {
		kvm_err("%s: Invalid BadVaddr: %#lx\n", __func__, badvaddr);
		kvm_mips_dump_host_tlbs();
		return -1;
	}

	/* Find host PFNs */

	gfn = (KVM_GUEST_CPHYSADDR(badvaddr) >> PAGE_SHIFT);
	if ((gfn | 1) >= kvm->arch.guest_pmap_npages) {
		kvm_err("%s: Invalid gfn: %#llx, BadVaddr: %#lx\n", __func__,
			gfn, badvaddr);
		kvm_mips_dump_host_tlbs();
		return -1;
	}
	vaddr = badvaddr & (PAGE_MASK << 1);

	if (kvm_mips_map_page(vcpu->kvm, gfn) < 0)
		return -1;

	if (kvm_mips_map_page(vcpu->kvm, gfn ^ 0x1) < 0)
		return -1;

	pfn0 = kvm->arch.guest_pmap[gfn & ~0x1];
	pfn1 = kvm->arch.guest_pmap[gfn | 0x1];

	/* Find GVA page table entry */

	ptep_gva = kvm_trap_emul_pte_for_gva(vcpu, vaddr);
	if (!ptep_gva) {
		kvm_err("No ptep for gva %lx\n", vaddr);
		return -1;
	}

	/* Write host PFNs into GVA page table */
	ptep_gva[0] = pte_mkyoung(pte_mkdirty(pfn_pte(pfn0, PAGE_SHARED)));
	ptep_gva[1] = pte_mkyoung(pte_mkdirty(pfn_pte(pfn1, PAGE_SHARED)));

	/* Invalidate this entry in the TLB, guest kernel ASID only */
	kvm_mips_host_tlb_inv(vcpu, vaddr, false, true);
	return 0;
}

int kvm_mips_handle_mapped_seg_tlb_fault(struct kvm_vcpu *vcpu,
					 struct kvm_mips_tlb *tlb,
					 unsigned long gva)
{
	struct kvm *kvm = vcpu->kvm;
	kvm_pfn_t pfn;
	gfn_t gfn;
	long tlb_lo = 0;
	pte_t *ptep_gva;
	unsigned int idx;
	bool kernel = KVM_GUEST_KERNEL_MODE(vcpu);

	/*
	 * The commpage address must not be mapped to anything else if the guest
	 * TLB contains entries nearby, or commpage accesses will break.
	 */
	idx = TLB_LO_IDX(*tlb, gva);
	if ((gva ^ KVM_GUEST_COMMPAGE_ADDR) & VPN2_MASK & PAGE_MASK)
		tlb_lo = tlb->tlb_lo[idx];

	/* Find host PFN */
	gfn = mips3_tlbpfn_to_paddr(tlb_lo) >> PAGE_SHIFT;
	if (gfn >= kvm->arch.guest_pmap_npages) {
		kvm_err("%s: Invalid gfn: %#llx, EHi: %#lx\n",
			__func__, gfn, tlb->tlb_hi);
		kvm_mips_dump_guest_tlbs(vcpu);
		return -1;
	}
	if (kvm_mips_map_page(kvm, gfn) < 0)
		return -1;
	pfn = kvm->arch.guest_pmap[gfn];

	/* Find GVA page table entry */
	ptep_gva = kvm_trap_emul_pte_for_gva(vcpu, gva);
	if (!ptep_gva) {
		kvm_err("No ptep for gva %lx\n", gva);
		return -1;
	}

	/* Write PFN into GVA page table, taking attributes from Guest TLB */
	*ptep_gva = pfn_pte(pfn, (!(tlb_lo & ENTRYLO_V)) ? __pgprot(0) :
				 (tlb_lo & ENTRYLO_D) ? PAGE_SHARED :
				 PAGE_READONLY);
	if (pte_present(*ptep_gva))
		*ptep_gva = pte_mkyoung(pte_mkdirty(*ptep_gva));

	/* Invalidate this entry in the TLB, current guest mode ASID only */
	kvm_mips_host_tlb_inv(vcpu, gva, !kernel, kernel);

	kvm_debug("@ %#lx tlb_lo0: 0x%08lx tlb_lo1: 0x%08lx\n", vcpu->arch.pc,
		  tlb->tlb_lo[0], tlb->tlb_lo[1]);

	return 0;
}

int kvm_mips_handle_commpage_tlb_fault(unsigned long badvaddr,
				       struct kvm_vcpu *vcpu)
{
	kvm_pfn_t pfn;
	pte_t *ptep;

	ptep = kvm_trap_emul_pte_for_gva(vcpu, badvaddr);
	if (!ptep) {
		kvm_err("No ptep for commpage %lx\n", badvaddr);
		return -1;
	}

	pfn = PFN_DOWN(virt_to_phys(vcpu->arch.kseg0_commpage));
	/* Also set valid and dirty, so refill handler doesn't have to */
	*ptep = pte_mkyoung(pte_mkdirty(pfn_pte(pfn, PAGE_SHARED)));

	/* Invalidate this entry in the TLB, guest kernel ASID only */
	kvm_mips_host_tlb_inv(vcpu, badvaddr, false, true);
	return 0;
}

/**
 * kvm_mips_migrate_count() - Migrate timer.
 * @vcpu:	Virtual CPU.
 *
 * Migrate CP0_Count hrtimer to the current CPU by cancelling and restarting it
 * if it was running prior to being cancelled.
 *
 * Must be called when the VCPU is migrated to a different CPU to ensure that
 * timer expiry during guest execution interrupts the guest and causes the
 * interrupt to be delivered in a timely manner.
 */
static void kvm_mips_migrate_count(struct kvm_vcpu *vcpu)
{
	if (hrtimer_cancel(&vcpu->arch.comparecount_timer))
		hrtimer_restart(&vcpu->arch.comparecount_timer);
}

/* Restore ASID once we are scheduled back after preemption */
void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
{
	unsigned long flags;

	kvm_debug("%s: vcpu %p, cpu: %d\n", __func__, vcpu, cpu);

	local_irq_save(flags);

	if (vcpu->arch.last_sched_cpu != cpu) {
		kvm_debug("[%d->%d]KVM VCPU[%d] switch\n",
			  vcpu->arch.last_sched_cpu, cpu, vcpu->vcpu_id);
		/*
		 * Migrate the timer interrupt to the current CPU so that it
		 * always interrupts the guest and synchronously triggers a
		 * guest timer interrupt.
		 */
		kvm_mips_migrate_count(vcpu);
	}

	/* restore guest state to registers */
	kvm_mips_callbacks->vcpu_load(vcpu, cpu);

	local_irq_restore(flags);
}

/* ASID can change if another task is scheduled during preemption */
void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
{
	unsigned long flags;
	int cpu;

	local_irq_save(flags);

	cpu = smp_processor_id();
	vcpu->arch.last_sched_cpu = cpu;

	/* save guest state in registers */
	kvm_mips_callbacks->vcpu_put(vcpu, cpu);

	local_irq_restore(flags);
}

int kvm_get_inst(u32 *opc, struct kvm_vcpu *vcpu, u32 *out)
{
	int err;

	err = get_user(*out, opc);
	if (unlikely(err)) {
		kvm_err("%s: illegal address: %p\n", __func__, opc);
		return -EFAULT;
	}

	return 0;
}