/*
* 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
void kvm_mmu_free_memory_caches(struct kvm_vcpu *vcpu)
{
kvm_mmu_free_memory_cache(&vcpu->arch.mmu_page_cache);
}
/**
* kvm_pgd_init() - Initialise KVM GPA page directory.
* @page: Pointer to page directory (PGD) for KVM GPA.
*
* Initialise a KVM GPA page directory with pointers to the invalid table, i.e.
* representing no mappings. This is similar to pgd_init(), however it
* initialises all the page directory pointers, not just the ones corresponding
* to the userland address space (since it is for the guest physical address
* space rather than a virtual address space).
*/
static void kvm_pgd_init(void *page)
{
unsigned long *p, *end;
unsigned long entry;
#ifdef __PAGETABLE_PMD_FOLDED
entry = (unsigned long)invalid_pte_table;
#else
entry = (unsigned long)invalid_pmd_table;
#endif
p = (unsigned long *)page;
end = p + PTRS_PER_PGD;
do {
p[0] = entry;
p[1] = entry;
p[2] = entry;
p[3] = entry;
p[4] = entry;
p += 8;
p[-3] = entry;
p[-2] = entry;
p[-1] = entry;
} while (p != end);
}
/**
* kvm_pgd_alloc() - Allocate and initialise a KVM GPA page directory.
*
* Allocate a blank KVM GPA page directory (PGD) for representing guest physical
* to host physical page mappings.
*
* Returns: Pointer to new KVM GPA page directory.
* NULL on allocation failure.
*/
pgd_t *kvm_pgd_alloc(void)
{
pgd_t *ret;
ret = (pgd_t *)__get_free_pages(GFP_KERNEL, PGD_TABLE_ORDER);
if (ret)
kvm_pgd_init(ret);
return ret;
}
/**
* 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)
{
p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;
pgd += pgd_index(addr);
if (pgd_none(*pgd)) {
/* Not used on MIPS yet */
BUG();
return NULL;
}
p4d = p4d_offset(pgd, addr);
pud = pud_offset(p4d, addr);
if (pud_none(*pud)) {
pmd_t *new_pmd;
if (!cache)
return NULL;
new_pmd = kvm_mmu_memory_cache_alloc(cache);
pmd_init(new_pmd);
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 = kvm_mmu_memory_cache_alloc(cache);
clear_page(new_pte);
pmd_populate_kernel(NULL, pmd, new_pte);
}
return pte_offset_kernel(pmd, addr);
}
/* Caller must hold kvm->mm_lock */
static pte_t *kvm_mips_pte_for_gpa(struct kvm *kvm,
struct kvm_mmu_memory_cache *cache,
unsigned long addr)
{
return kvm_mips_walk_pgd(kvm->arch.gpa_mm.pgd, cache, addr);
}
/*
* kvm_mips_flush_gpa_{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_gpa_pte(pte_t *pte, unsigned long start_gpa,
unsigned long end_gpa)
{
int i_min = pte_index(start_gpa);
int i_max = pte_index(end_gpa);
bool safe_to_remove = (i_min == 0 && i_max == PTRS_PER_PTE - 1);
int i;
for (i = i_min; i <= i_max; ++i) {
if (!pte_present(pte[i]))
continue;
set_pte(pte + i, __pte(0));
}
return safe_to_remove;
}
static bool kvm_mips_flush_gpa_pmd(pmd_t *pmd, unsigned long start_gpa,
unsigned long end_gpa)
{
pte_t *pte;
unsigned long end = ~0ul;
int i_min = pmd_index(start_gpa);
int i_max = pmd_index(end_gpa);
bool safe_to_remove = (i_min == 0 && i_max == PTRS_PER_PMD - 1);
int i;
for (i = i_min; i <= i_max; ++i, start_gpa = 0) {
if (!pmd_present(pmd[i]))
continue;
pte = pte_offset_kernel(pmd + i, 0);
if (i == i_max)
end = end_gpa;
if (kvm_mips_flush_gpa_pte(pte, start_gpa, end)) {
pmd_clear(pmd + i);
pte_free_kernel(NULL, pte);
} else {
safe_to_remove = false;
}
}
return safe_to_remove;
}
static bool kvm_mips_flush_gpa_pud(pud_t *pud, unsigned long start_gpa,
unsigned long end_gpa)
{
pmd_t *pmd;
unsigned long end = ~0ul;
int i_min = pud_index(start_gpa);
int i_max = pud_index(end_gpa);
bool safe_to_remove = (i_min == 0 && i_max == PTRS_PER_PUD - 1);
int i;
for (i = i_min; i <= i_max; ++i, start_gpa = 0) {
if (!pud_present(pud[i]))
continue;
pmd = pmd_offset(pud + i, 0);
if (i == i_max)
end = end_gpa;
if (kvm_mips_flush_gpa_pmd(pmd, start_gpa, end)) {
pud_clear(pud + i);
pmd_free(NULL, pmd);
} else {
safe_to_remove = false;
}
}
return safe_to_remove;
}
static bool kvm_mips_flush_gpa_pgd(pgd_t *pgd, unsigned long start_gpa,
unsigned long end_gpa)
{
p4d_t *p4d;
pud_t *pud;
unsigned long end = ~0ul;
int i_min = pgd_index(start_gpa);
int i_max = pgd_index(end_gpa);
bool safe_to_remove = (i_min == 0 && i_max == PTRS_PER_PGD - 1);
int i;
for (i = i_min; i <= i_max; ++i, start_gpa = 0) {
if (!pgd_present(pgd[i]))
continue;
p4d = p4d_offset(pgd, 0);
pud = pud_offset(p4d + i, 0);
if (i == i_max)
end = end_gpa;
if (kvm_mips_flush_gpa_pud(pud, start_gpa, end)) {
pgd_clear(pgd + i);
pud_free(NULL, pud);
} else {
safe_to_remove = false;
}
}
return safe_to_remove;
}
/**
* kvm_mips_flush_gpa_pt() - Flush a range of guest physical addresses.
* @kvm: KVM pointer.
* @start_gfn: Guest frame number of first page in GPA range to flush.
* @end_gfn: Guest frame number of last page in GPA range to flush.
*
* Flushes a range of GPA mappings from the GPA page tables.
*
* The caller must hold the @kvm->mmu_lock spinlock.
*
* Returns: Whether its safe to remove the top level page directory because
* all lower levels have been removed.
*/
bool kvm_mips_flush_gpa_pt(struct kvm *kvm, gfn_t start_gfn, gfn_t end_gfn)
{
return kvm_mips_flush_gpa_pgd(kvm->arch.gpa_mm.pgd,
start_gfn << PAGE_SHIFT,
end_gfn << PAGE_SHIFT);
}
#define BUILD_PTE_RANGE_OP(name, op) \
static int kvm_mips_##name##_pte(pte_t *pte, unsigned long start, \
unsigned long end) \
{ \
int ret = 0; \
int i_min = pte_index(start); \
int i_max = pte_index(end); \
int i; \
pte_t old, new; \
\
for (i = i_min; i <= i_max; ++i) { \
if (!pte_present(pte[i])) \
continue; \
\
old = pte[i]; \
new = op(old); \
if (pte_val(new) == pte_val(old)) \
continue; \
set_pte(pte + i, new); \
ret = 1; \
} \
return ret; \
} \
\
/* returns true if anything was done */ \
static int kvm_mips_##name##_pmd(pmd_t *pmd, unsigned long start, \
unsigned long end) \
{ \
int ret = 0; \
pte_t *pte; \
unsigned long cur_end = ~0ul; \
int i_min = pmd_index(start); \
int i_max = pmd_index(end); \
int i; \
\
for (i = i_min; i <= i_max; ++i, start = 0) { \
if (!pmd_present(pmd[i])) \
continue; \
\
pte = pte_offset_kernel(pmd + i, 0); \
if (i == i_max) \
cur_end = end; \
\
ret |= kvm_mips_##name##_pte(pte, start, cur_end); \
} \
return ret; \
} \
\
static int kvm_mips_##name##_pud(pud_t *pud, unsigned long start, \
unsigned long end) \
{ \
int ret = 0; \
pmd_t *pmd; \
unsigned long cur_end = ~0ul; \
int i_min = pud_index(start); \
int i_max = pud_index(end); \
int i; \
\
for (i = i_min; i <= i_max; ++i, start = 0) { \
if (!pud_present(pud[i])) \
continue; \
\
pmd = pmd_offset(pud + i, 0); \
if (i == i_max) \
cur_end = end; \
\
ret |= kvm_mips_##name##_pmd(pmd, start, cur_end); \
} \
return ret; \
} \
\
static int kvm_mips_##name##_pgd(pgd_t *pgd, unsigned long start, \
unsigned long end) \
{ \
int ret = 0; \
p4d_t *p4d; \
pud_t *pud; \
unsigned long cur_end = ~0ul; \
int i_min = pgd_index(start); \
int i_max = pgd_index(end); \
int i; \
\
for (i = i_min; i <= i_max; ++i, start = 0) { \
if (!pgd_present(pgd[i])) \
continue; \
\
p4d = p4d_offset(pgd, 0); \
pud = pud_offset(p4d + i, 0); \
if (i == i_max) \
cur_end = end; \
\
ret |= kvm_mips_##name##_pud(pud, start, cur_end); \
} \
return ret; \
}
/*
* kvm_mips_mkclean_gpa_pt.
* Mark a range of guest physical address space clean (writes fault) in the VM's
* GPA page table to allow dirty page tracking.
*/
BUILD_PTE_RANGE_OP(mkclean, pte_mkclean)
/**
* kvm_mips_mkclean_gpa_pt() - Make a range of guest physical addresses clean.
* @kvm: KVM pointer.
* @start_gfn: Guest frame number of first page in GPA range to flush.
* @end_gfn: Guest frame number of last page in GPA range to flush.
*
* Make a range of GPA mappings clean so that guest writes will fault and
* trigger dirty page logging.
*
* The caller must hold the @kvm->mmu_lock spinlock.
*
* Returns: Whether any GPA mappings were modified, which would require
* derived mappings (GVA page tables & TLB enties) to be
* invalidated.
*/
int kvm_mips_mkclean_gpa_pt(struct kvm *kvm, gfn_t start_gfn, gfn_t end_gfn)
{
return kvm_mips_mkclean_pgd(kvm->arch.gpa_mm.pgd,
start_gfn << PAGE_SHIFT,
end_gfn << PAGE_SHIFT);
}
/**
* kvm_arch_mmu_enable_log_dirty_pt_masked() - write protect dirty pages
* @kvm: The KVM pointer
* @slot: The memory slot associated with mask
* @gfn_offset: The gfn offset in memory slot
* @mask: The mask of dirty pages at offset 'gfn_offset' in this memory
* slot to be write protected
*
* Walks bits set in mask write protects the associated pte's. Caller must
* acquire @kvm->mmu_lock.
*/
void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
struct kvm_memory_slot *slot,
gfn_t gfn_offset, unsigned long mask)
{
gfn_t base_gfn = slot->base_gfn + gfn_offset;
gfn_t start = base_gfn + __ffs(mask);
gfn_t end = base_gfn + __fls(mask);
kvm_mips_mkclean_gpa_pt(kvm, start, end);
}
/*
* kvm_mips_mkold_gpa_pt.
* Mark a range of guest physical address space old (all accesses fault) in the
* VM's GPA page table to allow detection of commonly used pages.
*/
BUILD_PTE_RANGE_OP(mkold, pte_mkold)
static int kvm_mips_mkold_gpa_pt(struct kvm *kvm, gfn_t start_gfn,
gfn_t end_gfn)
{
return kvm_mips_mkold_pgd(kvm->arch.gpa_mm.pgd,
start_gfn << PAGE_SHIFT,
end_gfn << PAGE_SHIFT);
}
bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
{
kvm_mips_flush_gpa_pt(kvm, range->start, range->end);
return true;
}
bool kvm_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
{
gpa_t gpa = range->start << PAGE_SHIFT;
pte_t hva_pte = range->arg.pte;
pte_t *gpa_pte = kvm_mips_pte_for_gpa(kvm, NULL, gpa);
pte_t old_pte;
if (!gpa_pte)
return false;
/* Mapping may need adjusting depending on memslot flags */
old_pte = *gpa_pte;
if (range->slot->flags & KVM_MEM_LOG_DIRTY_PAGES && !pte_dirty(old_pte))
hva_pte = pte_mkclean(hva_pte);
else if (range->slot->flags & KVM_MEM_READONLY)
hva_pte = pte_wrprotect(hva_pte);
set_pte(gpa_pte, hva_pte);
/* Replacing an absent or old page doesn't need flushes */
if (!pte_present(old_pte) || !pte_young(old_pte))
return false;
/* Pages swapped, aged, moved, or cleaned require flushes */
return !pte_present(hva_pte) ||
!pte_young(hva_pte) ||
pte_pfn(old_pte) != pte_pfn(hva_pte) ||
(pte_dirty(old_pte) && !pte_dirty(hva_pte));
}
bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
{
return kvm_mips_mkold_gpa_pt(kvm, range->start, range->end);
}
bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
{
gpa_t gpa = range->start << PAGE_SHIFT;
pte_t *gpa_pte = kvm_mips_pte_for_gpa(kvm, NULL, gpa);
if (!gpa_pte)
return false;
return pte_young(*gpa_pte);
}
/**
* _kvm_mips_map_page_fast() - Fast path GPA fault handler.
* @vcpu: VCPU pointer.
* @gpa: Guest physical address of fault.
* @write_fault: Whether the fault was due to a write.
* @out_entry: New PTE for @gpa (written on success unless NULL).
* @out_buddy: New PTE for @gpa's buddy (written on success unless
* NULL).
*
* Perform fast path GPA fault handling, doing all that can be done without
* calling into KVM. This handles marking old pages young (for idle page
* tracking), and dirtying of clean pages (for dirty page logging).
*
* Returns: 0 on success, in which case we can update derived mappings and
* resume guest execution.
* -EFAULT on failure due to absent GPA mapping or write to
* read-only page, in which case KVM must be consulted.
*/
static int _kvm_mips_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa,
bool write_fault,
pte_t *out_entry, pte_t *out_buddy)
{
struct kvm *kvm = vcpu->kvm;
gfn_t gfn = gpa >> PAGE_SHIFT;
pte_t *ptep;
kvm_pfn_t pfn = 0; /* silence bogus GCC warning */
bool pfn_valid = false;
int ret = 0;
spin_lock(&kvm->mmu_lock);
/* Fast path - just check GPA page table for an existing entry */
ptep = kvm_mips_pte_for_gpa(kvm, NULL, gpa);
if (!ptep || !pte_present(*ptep)) {
ret = -EFAULT;
goto out;
}
/* Track access to pages marked old */
if (!pte_young(*ptep)) {
set_pte(ptep, pte_mkyoung(*ptep));
pfn = pte_pfn(*ptep);
pfn_valid = true;
/* call kvm_set_pfn_accessed() after unlock */
}
if (write_fault && !pte_dirty(*ptep)) {
if (!pte_write(*ptep)) {
ret = -EFAULT;
goto out;
}
/* Track dirtying of writeable pages */
set_pte(ptep, pte_mkdirty(*ptep));
pfn = pte_pfn(*ptep);
mark_page_dirty(kvm, gfn);
kvm_set_pfn_dirty(pfn);
}
if (out_entry)
*out_entry = *ptep;
if (out_buddy)
*out_buddy = *ptep_buddy(ptep);
out:
spin_unlock(&kvm->mmu_lock);
if (pfn_valid)
kvm_set_pfn_accessed(pfn);
return ret;
}
/**
* kvm_mips_map_page() - Map a guest physical page.
* @vcpu: VCPU pointer.
* @gpa: Guest physical address of fault.
* @write_fault: Whether the fault was due to a write.
* @out_entry: New PTE for @gpa (written on success unless NULL).
* @out_buddy: New PTE for @gpa's buddy (written on success unless
* NULL).
*
* Handle GPA faults by creating a new GPA mapping (or updating an existing
* one).
*
* This takes care of marking pages young or dirty (idle/dirty page tracking),
* asking KVM for the corresponding PFN, and creating a mapping in the GPA page
* tables. Derived mappings (GVA page tables and TLBs) must be handled by the
* caller.
*
* Returns: 0 on success, in which case the caller may use the @out_entry
* and @out_buddy PTEs to update derived mappings and resume guest
* execution.
* -EFAULT if there is no memory region at @gpa or a write was
* attempted to a read-only memory region. This is usually handled
* as an MMIO access.
*/
static int kvm_mips_map_page(struct kvm_vcpu *vcpu, unsigned long gpa,
bool write_fault,
pte_t *out_entry, pte_t *out_buddy)
{
struct kvm *kvm = vcpu->kvm;
struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache;
gfn_t gfn = gpa >> PAGE_SHIFT;
int srcu_idx, err;
kvm_pfn_t pfn;
pte_t *ptep, entry;
bool writeable;
unsigned long prot_bits;
unsigned long mmu_seq;
/* Try the fast path to handle old / clean pages */
srcu_idx = srcu_read_lock(&kvm->srcu);
err = _kvm_mips_map_page_fast(vcpu, gpa, write_fault, out_entry,
out_buddy);
if (!err)
goto out;
/* We need a minimum of cached pages ready for page table creation */
err = kvm_mmu_topup_memory_cache(memcache, KVM_MMU_CACHE_MIN_PAGES);
if (err)
goto out;
retry:
/*
* Used to check for invalidations in progress, of the pfn that is
* returned by pfn_to_pfn_prot below.
*/
mmu_seq = kvm->mmu_invalidate_seq;
/*
* Ensure the read of mmu_invalidate_seq isn't reordered with PTE reads
* in gfn_to_pfn_prot() (which calls get_user_pages()), so that we don't
* risk the page we get a reference to getting unmapped before we have a
* chance to grab the mmu_lock without mmu_invalidate_retry() noticing.
*
* This smp_rmb() pairs with the effective smp_wmb() of the combination
* of the pte_unmap_unlock() after the PTE is zapped, and the
* spin_lock() in kvm_mmu_notifier_invalidate_<page|range_end>() before
* mmu_invalidate_seq is incremented.
*/
smp_rmb();
/* Slow path - ask KVM core whether we can access this GPA */
pfn = gfn_to_pfn_prot(kvm, gfn, write_fault, &writeable);
if (is_error_noslot_pfn(pfn)) {
err = -EFAULT;
goto out;
}
spin_lock(&kvm->mmu_lock);
/* Check if an invalidation has taken place since we got pfn */
if (mmu_invalidate_retry(kvm, mmu_seq)) {
/*
* This can happen when mappings are changed asynchronously, but
* also synchronously if a COW is triggered by
* gfn_to_pfn_prot().
*/
spin_unlock(&kvm->mmu_lock);
kvm_release_pfn_clean(pfn);
goto retry;
}
/* Ensure page tables are allocated */
ptep = kvm_mips_pte_for_gpa(kvm, memcache, gpa);
/* Set up the PTE */
prot_bits = _PAGE_PRESENT | __READABLE | _page_cachable_default;
if (writeable) {
prot_bits |= _PAGE_WRITE;
if (write_fault) {
prot_bits |= __WRITEABLE;
mark_page_dirty(kvm, gfn);
kvm_set_pfn_dirty(pfn);
}
}
entry = pfn_pte(pfn, __pgprot(prot_bits));
/* Write the PTE */
set_pte(ptep, entry);
err = 0;
if (out_entry)
*out_entry = *ptep;
if (out_buddy)
*out_buddy = *ptep_buddy(ptep);
spin_unlock(&kvm->mmu_lock);
kvm_release_pfn_clean(pfn);
kvm_set_pfn_accessed(pfn);
out:
srcu_read_unlock(&kvm->srcu, srcu_idx);
return err;
}
int kvm_mips_handle_vz_root_tlb_fault(unsigned long badvaddr,
struct kvm_vcpu *vcpu,
bool write_fault)
{
int ret;
ret = kvm_mips_map_page(vcpu, badvaddr, write_fault, NULL, NULL);
if (ret)
return ret;
/* Invalidate this entry in the TLB */
return kvm_vz_host_tlb_inv(vcpu, badvaddr);
}
/**
* 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);
vcpu->cpu = cpu;
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;
vcpu->cpu = -1;
/* save guest state in registers */
kvm_mips_callbacks->vcpu_put(vcpu, cpu);
local_irq_restore(flags);
}