/*
* 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.
* Copyright 2010 Red Hat, Inc. and/or its affiliates.
*
* 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.
*
*/
/*
* 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.
*/
/*
* This is used to catch non optimized PT_GUEST_(DIRTY|ACCESS)_SHIFT macro
* uses for EPT without A/D paging type.
*/
extern u64 __pure __using_nonexistent_pte_bit(void)
__compiletime_error("wrong use of PT_GUEST_(DIRTY|ACCESS)_SHIFT");
#if PTTYPE == 64
#define pt_element_t u64
#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_BITS PT64_LEVEL_BITS
#define PT_GUEST_ACCESSED_MASK PT_ACCESSED_MASK
#define PT_GUEST_DIRTY_MASK PT_DIRTY_MASK
#define PT_GUEST_DIRTY_SHIFT PT_DIRTY_SHIFT
#define PT_GUEST_ACCESSED_SHIFT PT_ACCESSED_SHIFT
#ifdef CONFIG_X86_64
#define PT_MAX_FULL_LEVELS 4
#define CMPXCHG cmpxchg
#else
#define CMPXCHG cmpxchg64
#define PT_MAX_FULL_LEVELS 2
#endif
#elif PTTYPE == 32
#define pt_element_t u32
#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_BITS PT32_LEVEL_BITS
#define PT_MAX_FULL_LEVELS 2
#define PT_GUEST_ACCESSED_MASK PT_ACCESSED_MASK
#define PT_GUEST_DIRTY_MASK PT_DIRTY_MASK
#define PT_GUEST_DIRTY_SHIFT PT_DIRTY_SHIFT
#define PT_GUEST_ACCESSED_SHIFT PT_ACCESSED_SHIFT
#define CMPXCHG cmpxchg
#elif PTTYPE == PTTYPE_EPT
#define pt_element_t u64
#define guest_walker guest_walkerEPT
#define FNAME(name) ept_##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_BITS PT64_LEVEL_BITS
#define PT_GUEST_ACCESSED_MASK 0
#define PT_GUEST_DIRTY_MASK 0
#define PT_GUEST_DIRTY_SHIFT __using_nonexistent_pte_bit()
#define PT_GUEST_ACCESSED_SHIFT __using_nonexistent_pte_bit()
#define CMPXCHG cmpxchg64
#define PT_MAX_FULL_LEVELS 4
#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;
unsigned max_level;
gfn_t table_gfn[PT_MAX_FULL_LEVELS];
pt_element_t ptes[PT_MAX_FULL_LEVELS];
pt_element_t prefetch_ptes[PTE_PREFETCH_NUM];
gpa_t pte_gpa[PT_MAX_FULL_LEVELS];
pt_element_t __user *ptep_user[PT_MAX_FULL_LEVELS];
bool pte_writable[PT_MAX_FULL_LEVELS];
unsigned pt_access;
unsigned pte_access;
gfn_t gfn;
struct x86_exception fault;
};
static gfn_t gpte_to_gfn_lvl(pt_element_t gpte, int lvl)
{
return (gpte & PT_LVL_ADDR_MASK(lvl)) >> PAGE_SHIFT;
}
static inline void FNAME(protect_clean_gpte)(unsigned *access, unsigned gpte)
{
unsigned mask;
/* dirty bit is not supported, so no need to track it */
if (!PT_GUEST_DIRTY_MASK)
return;
BUILD_BUG_ON(PT_WRITABLE_MASK != ACC_WRITE_MASK);
mask = (unsigned)~ACC_WRITE_MASK;
/* Allow write access to dirty gptes */
mask |= (gpte >> (PT_GUEST_DIRTY_SHIFT - PT_WRITABLE_SHIFT)) &
PT_WRITABLE_MASK;
*access &= mask;
}
static inline int FNAME(is_present_gpte)(unsigned long pte)
{
#if PTTYPE != PTTYPE_EPT
return is_present_gpte(pte);
#else
return pte & 7;
#endif
}
static int FNAME(cmpxchg_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
pt_element_t __user *ptep_user, unsigned index,
pt_element_t orig_pte, pt_element_t new_pte)
{
int npages;
pt_element_t ret;
pt_element_t *table;
struct page *page;
npages = get_user_pages_fast((unsigned long)ptep_user, 1, 1, &page);
/* Check if the user is doing something meaningless. */
if (unlikely(npages != 1))
return -EFAULT;
table = kmap_atomic(page);
ret = CMPXCHG(&table[index], orig_pte, new_pte);
kunmap_atomic(table);
kvm_release_page_dirty(page);
return (ret != orig_pte);
}
static bool FNAME(prefetch_invalid_gpte)(struct kvm_vcpu *vcpu,
struct kvm_mmu_page *sp, u64 *spte,
u64 gpte)
{
if (is_rsvd_bits_set(&vcpu->arch.mmu, gpte, PT_PAGE_TABLE_LEVEL))
goto no_present;
if (!FNAME(is_present_gpte)(gpte))
goto no_present;
/* if accessed bit is not supported prefetch non accessed gpte */
if (PT_GUEST_ACCESSED_MASK && !(gpte & PT_GUEST_ACCESSED_MASK))
goto no_present;
return false;
no_present:
drop_spte(vcpu->kvm, spte);
return true;
}
static inline unsigned FNAME(gpte_access)(struct kvm_vcpu *vcpu, u64 gpte)
{
unsigned access;
#if PTTYPE == PTTYPE_EPT
access = ((gpte & VMX_EPT_WRITABLE_MASK) ? ACC_WRITE_MASK : 0) |
((gpte & VMX_EPT_EXECUTABLE_MASK) ? ACC_EXEC_MASK : 0) |
ACC_USER_MASK;
#else
access = (gpte & (PT_WRITABLE_MASK | PT_USER_MASK)) | ACC_EXEC_MASK;
access &= ~(gpte >> PT64_NX_SHIFT);
#endif
return access;
}
static int FNAME(update_accessed_dirty_bits)(struct kvm_vcpu *vcpu,
struct kvm_mmu *mmu,
struct guest_walker *walker,
int write_fault)
{
unsigned level, index;
pt_element_t pte, orig_pte;
pt_element_t __user *ptep_user;
gfn_t table_gfn;
int ret;
/* dirty/accessed bits are not supported, so no need to update them */
if (!PT_GUEST_DIRTY_MASK)
return 0;
for (level = walker->max_level; level >= walker->level; --level) {
pte = orig_pte = walker->ptes[level - 1];
table_gfn = walker->table_gfn[level - 1];
ptep_user = walker->ptep_user[level - 1];
index = offset_in_page(ptep_user) / sizeof(pt_element_t);
if (!(pte & PT_GUEST_ACCESSED_MASK)) {
trace_kvm_mmu_set_accessed_bit(table_gfn, index, sizeof(pte));
pte |= PT_GUEST_ACCESSED_MASK;
}
if (level == walker->level && write_fault &&
!(pte & PT_GUEST_DIRTY_MASK)) {
trace_kvm_mmu_set_dirty_bit(table_gfn, index, sizeof(pte));
pte |= PT_GUEST_DIRTY_MASK;
}
if (pte == orig_pte)
continue;
/*
* If the slot is read-only, simply do not process the accessed
* and dirty bits. This is the correct thing to do if the slot
* is ROM, and page tables in read-as-ROM/write-as-MMIO slots
* are only supported if the accessed and dirty bits are already
* set in the ROM (so that MMIO writes are never needed).
*
* Note that NPT does not allow this at all and faults, since
* it always wants nested page table entries for the guest
* page tables to be writable. And EPT works but will simply
* overwrite the read-only memory to set the accessed and dirty
* bits.
*/
if (unlikely(!walker->pte_writable[level - 1]))
continue;
ret = FNAME(cmpxchg_gpte)(vcpu, mmu, ptep_user, index, orig_pte, pte);
if (ret)
return ret;
kvm_vcpu_mark_page_dirty(vcpu, table_gfn);
walker->ptes[level] = pte;
}
return 0;
}
/*
* Fetch a guest pte for a guest virtual address
*/
static int FNAME(walk_addr_generic)(struct guest_walker *walker,
struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
gva_t addr, u32 access)
{
int ret;
pt_element_t pte;
pt_element_t __user *uninitialized_var(ptep_user);
gfn_t table_gfn;
unsigned index, pt_access, pte_access, accessed_dirty;
gpa_t pte_gpa;
int offset;
const int write_fault = access & PFERR_WRITE_MASK;
const int user_fault = access & PFERR_USER_MASK;
const int fetch_fault = access & PFERR_FETCH_MASK;
u16 errcode = 0;
gpa_t real_gpa;
gfn_t gfn;
trace_kvm_mmu_pagetable_walk(addr, access);
retry_walk:
walker->level = mmu->root_level;
pte = mmu->get_cr3(vcpu);
#if PTTYPE == 64
if (walker->level == PT32E_ROOT_LEVEL) {
pte = mmu->get_pdptr(vcpu, (addr >> 30) & 3);
trace_kvm_mmu_paging_element(pte, walker->level);
if (!FNAME(is_present_gpte)(pte))
goto error;
--walker->level;
}
#endif
walker->max_level = walker->level;
ASSERT(!(is_long_mode(vcpu) && !is_pae(vcpu)));
accessed_dirty = PT_GUEST_ACCESSED_MASK;
pt_access = pte_access = ACC_ALL;
++walker->level;
do {
gfn_t real_gfn;
unsigned long host_addr;
pt_access &= pte_access;
--walker->level;
index = PT_INDEX(addr, walker->level);
table_gfn = gpte_to_gfn(pte);
offset = index * sizeof(pt_element_t);
pte_gpa = gfn_to_gpa(table_gfn) + offset;
walker->table_gfn[walker->level - 1] = table_gfn;
walker->pte_gpa[walker->level - 1] = pte_gpa;
real_gfn = mmu->translate_gpa(vcpu, gfn_to_gpa(table_gfn),
PFERR_USER_MASK|PFERR_WRITE_MASK,
&walker->fault);
/*
* FIXME: This can happen if emulation (for of an INS/OUTS
* instruction) triggers a nested page fault. The exit
* qualification / exit info field will incorrectly have
* "guest page access" as the nested page fault's cause,
* instead of "guest page structure access". To fix this,
* the x86_exception struct should be augmented with enough
* information to fix the exit_qualification or exit_info_1
* fields.
*/
if (unlikely(real_gfn == UNMAPPED_GVA))
return 0;
real_gfn = gpa_to_gfn(real_gfn);
host_addr = kvm_vcpu_gfn_to_hva_prot(vcpu, real_gfn,
&walker->pte_writable[walker->level - 1]);
if (unlikely(kvm_is_error_hva(host_addr)))
goto error;
ptep_user = (pt_element_t __user *)((void *)host_addr + offset);
if (unlikely(__copy_from_user(&pte, ptep_user, sizeof(pte))))
goto error;
walker->ptep_user[walker->level - 1] = ptep_user;
trace_kvm_mmu_paging_element(pte, walker->level);
if (unlikely(!FNAME(is_present_gpte)(pte)))
goto error;
if (unlikely(is_rsvd_bits_set(mmu, pte, walker->level))) {
errcode |= PFERR_RSVD_MASK | PFERR_PRESENT_MASK;
goto error;
}
accessed_dirty &= pte;
pte_access = pt_access & FNAME(gpte_access)(vcpu, pte);
walker->ptes[walker->level - 1] = pte;
} while (!is_last_gpte(mmu, walker->level, pte));
if (unlikely(permission_fault(vcpu, mmu, pte_access, access))) {
errcode |= PFERR_PRESENT_MASK;
goto error;
}
gfn = gpte_to_gfn_lvl(pte, walker->level);
gfn += (addr & PT_LVL_OFFSET_MASK(walker->level)) >> PAGE_SHIFT;
if (PTTYPE == 32 && walker->level == PT_DIRECTORY_LEVEL && is_cpuid_PSE36())
gfn += pse36_gfn_delta(pte);
real_gpa = mmu->translate_gpa(vcpu, gfn_to_gpa(gfn), access, &walker->fault);
if (real_gpa == UNMAPPED_GVA)
return 0;
walker->gfn = real_gpa >> PAGE_SHIFT;
if (!write_fault)
FNAME(protect_clean_gpte)(&pte_access, pte);
else
/*
* On a write fault, fold the dirty bit into accessed_dirty.
* For modes without A/D bits support accessed_dirty will be
* always clear.
*/
accessed_dirty &= pte >>
(PT_GUEST_DIRTY_SHIFT - PT_GUEST_ACCESSED_SHIFT);
if (unlikely(!accessed_dirty)) {
ret = FNAME(update_accessed_dirty_bits)(vcpu, mmu, walker, write_fault);
if (unlikely(ret < 0))
goto error;
else if (ret)
goto retry_walk;
}
walker->pt_access = pt_access;
walker->pte_access = pte_access;
pgprintk("%s: pte %llx pte_access %x pt_access %x\n",
__func__, (u64)pte, pte_access, pt_access);
return 1;
error:
errcode |= write_fault | user_fault;
if (fetch_fault && (mmu->nx ||
kvm_read_cr4_bits(vcpu, X86_CR4_SMEP)))
errcode |= PFERR_FETCH_MASK;
walker->fault.vector = PF_VECTOR;
walker->fault.error_code_valid = true;
walker->fault.error_code = errcode;
#if PTTYPE == PTTYPE_EPT
/*
* Use PFERR_RSVD_MASK in error_code to to tell if EPT
* misconfiguration requires to be injected. The detection is
* done by is_rsvd_bits_set() above.
*
* We set up the value of exit_qualification to inject:
* [2:0] - Derive from [2:0] of real exit_qualification at EPT violation
* [5:3] - Calculated by the page walk of the guest EPT page tables
* [7:8] - Derived from [7:8] of real exit_qualification
*
* The other bits are set to 0.
*/
if (!(errcode & PFERR_RSVD_MASK)) {
vcpu->arch.exit_qualification &= 0x187;
vcpu->arch.exit_qualification |= ((pt_access & pte) & 0x7) << 3;
}
#endif
walker->fault.address = addr;
walker->fault.nested_page_fault = mmu != vcpu->arch.walk_mmu;
trace_kvm_mmu_walker_error(walker->fault.error_code);
return 0;
}
static int FNAME(walk_addr)(struct guest_walker *walker,
struct kvm_vcpu *vcpu, gva_t addr, u32 access)
{
return FNAME(walk_addr_generic)(walker, vcpu, &vcpu->arch.mmu, addr,
access);
}
#if PTTYPE != PTTYPE_EPT
static int FNAME(walk_addr_nested)(struct guest_walker *walker,
struct kvm_vcpu *vcpu, gva_t addr,
u32 access)
{
return FNAME(walk_addr_generic)(walker, vcpu, &vcpu->arch.nested_mmu,
addr, access);
}
#endif
static bool
FNAME(prefetch_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
u64 *spte, pt_element_t gpte, bool no_dirty_log)
{
unsigned pte_access;
gfn_t gfn;
pfn_t pfn;
if (FNAME(prefetch_invalid_gpte)(vcpu, sp, spte, gpte))
return false;
pgprintk("%s: gpte %llx spte %p\n", __func__, (u64)gpte, spte);
gfn = gpte_to_gfn(gpte);
pte_access = sp->role.access & FNAME(gpte_access)(vcpu, gpte);
FNAME(protect_clean_gpte)(&pte_access, gpte);
pfn = pte_prefetch_gfn_to_pfn(vcpu, gfn,
no_dirty_log && (pte_access & ACC_WRITE_MASK));
if (is_error_pfn(pfn))
return false;
/*
* we call mmu_set_spte() with host_writable = true because
* pte_prefetch_gfn_to_pfn always gets a writable pfn.
*/
mmu_set_spte(vcpu, spte, pte_access, 0, NULL, PT_PAGE_TABLE_LEVEL,
gfn, pfn, true, true);
return true;
}
static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
u64 *spte, const void *pte)
{
pt_element_t gpte = *(const pt_element_t *)pte;
FNAME(prefetch_gpte)(vcpu, sp, spte, gpte, false);
}
static bool FNAME(gpte_changed)(struct kvm_vcpu *vcpu,
struct guest_walker *gw, int level)
{
pt_element_t curr_pte;
gpa_t base_gpa, pte_gpa = gw->pte_gpa[level - 1];
u64 mask;
int r, index;
if (level == PT_PAGE_TABLE_LEVEL) {
mask = PTE_PREFETCH_NUM * sizeof(pt_element_t) - 1;
base_gpa = pte_gpa & ~mask;
index = (pte_gpa - base_gpa) / sizeof(pt_element_t);
r = kvm_vcpu_read_guest_atomic(vcpu, base_gpa,
gw->prefetch_ptes, sizeof(gw->prefetch_ptes));
curr_pte = gw->prefetch_ptes[index];
} else
r = kvm_vcpu_read_guest_atomic(vcpu, pte_gpa,
&curr_pte, sizeof(curr_pte));
return r || curr_pte != gw->ptes[level - 1];
}
static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu, struct guest_walker *gw,
u64 *sptep)
{
struct kvm_mmu_page *sp;
pt_element_t *gptep = gw->prefetch_ptes;
u64 *spte;
int i;
sp = page_header(__pa(sptep));
if (sp->role.level > PT_PAGE_TABLE_LEVEL)
return;
if (sp->role.direct)
return __direct_pte_prefetch(vcpu, sp, sptep);
i = (sptep - sp->spt) & ~(PTE_PREFETCH_NUM - 1);
spte = sp->spt + i;
for (i = 0; i < PTE_PREFETCH_NUM; i++, spte++) {
if (spte == sptep)
continue;
if (is_shadow_present_pte(*spte))
continue;
if (!FNAME(prefetch_gpte)(vcpu, sp, spte, gptep[i], true))
break;
}
}
/*
* Fetch a shadow pte for a specific level in the paging hierarchy.
* If the guest tries to write a write-protected page, we need to
* emulate this operation, return 1 to indicate this case.
*/
static int FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
struct guest_walker *gw,
int write_fault, int hlevel,
pfn_t pfn, bool map_writable, bool prefault)
{
struct kvm_mmu_page *sp = NULL;
struct kvm_shadow_walk_iterator it;
unsigned direct_access, access = gw->pt_access;
int top_level, emulate = 0;
direct_access = gw->pte_access;
top_level = vcpu->arch.mmu.root_level;
if (top_level == PT32E_ROOT_LEVEL)
top_level = PT32_ROOT_LEVEL;
/*
* Verify that the top-level gpte is still there. Since the page
* is a root page, it is either write protected (and cannot be
* changed from now on) or it is invalid (in which case, we don't
* really care if it changes underneath us after this point).
*/
if (FNAME(gpte_changed)(vcpu, gw, top_level))
goto out_gpte_changed;
if (!VALID_PAGE(vcpu->arch.mmu.root_hpa))
goto out_gpte_changed;
for (shadow_walk_init(&it, vcpu, addr);
shadow_walk_okay(&it) && it.level > gw->level;
shadow_walk_next(&it)) {
gfn_t table_gfn;
clear_sp_write_flooding_count(it.sptep);
drop_large_spte(vcpu, it.sptep);
sp = NULL;
if (!is_shadow_present_pte(*it.sptep)) {
table_gfn = gw->table_gfn[it.level - 2];
sp = kvm_mmu_get_page(vcpu, table_gfn, addr, it.level-1,
false, access, it.sptep);
}
/*
* Verify that the gpte in the page we've just write
* protected is still there.
*/
if (FNAME(gpte_changed)(vcpu, gw, it.level - 1))
goto out_gpte_changed;
if (sp)
link_shadow_page(it.sptep, sp, PT_GUEST_ACCESSED_MASK);
}
for (;
shadow_walk_okay(&it) && it.level > hlevel;
shadow_walk_next(&it)) {
gfn_t direct_gfn;
clear_sp_write_flooding_count(it.sptep);
validate_direct_spte(vcpu, it.sptep, direct_access);
drop_large_spte(vcpu, it.sptep);
if (is_shadow_present_pte(*it.sptep))
continue;
direct_gfn = gw->gfn & ~(KVM_PAGES_PER_HPAGE(it.level) - 1);
sp = kvm_mmu_get_page(vcpu, direct_gfn, addr, it.level-1,
true, direct_access, it.sptep);
link_shadow_page(it.sptep, sp, PT_GUEST_ACCESSED_MASK);
}
clear_sp_write_flooding_count(it.sptep);
mmu_set_spte(vcpu, it.sptep, gw->pte_access, write_fault, &emulate,
it.level, gw->gfn, pfn, prefault, map_writable);
FNAME(pte_prefetch)(vcpu, gw, it.sptep);
return emulate;
out_gpte_changed:
if (sp)
kvm_mmu_put_page(sp, it.sptep);
kvm_release_pfn_clean(pfn);
return 0;
}
/*
* To see whether the mapped gfn can write its page table in the current
* mapping.
*
* It is the helper function of FNAME(page_fault). When guest uses large page
* size to map the writable gfn which is used as current page table, we should
* force kvm to use small page size to map it because new shadow page will be
* created when kvm establishes shadow page table that stop kvm using large
* page size. Do it early can avoid unnecessary #PF and emulation.
*
* @write_fault_to_shadow_pgtable will return true if the fault gfn is
* currently used as its page table.
*
* Note: the PDPT page table is not checked for PAE-32 bit guest. It is ok
* since the PDPT is always shadowed, that means, we can not use large page
* size to map the gfn which is used as PDPT.
*/
static bool
FNAME(is_self_change_mapping)(struct kvm_vcpu *vcpu,
struct guest_walker *walker, int user_fault,
bool *write_fault_to_shadow_pgtable)
{
int level;
gfn_t mask = ~(KVM_PAGES_PER_HPAGE(walker->level) - 1);
bool self_changed = false;
if (!(walker->pte_access & ACC_WRITE_MASK ||
(!is_write_protection(vcpu) && !user_fault)))
return false;
for (level = walker->level; level <= walker->max_level; level++) {
gfn_t gfn = walker->gfn ^ walker->table_gfn[level - 1];
self_changed |= !(gfn & mask);
*write_fault_to_shadow_pgtable |= !gfn;
}
return self_changed;
}
/*
* 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, u32 error_code,
bool prefault)
{
int write_fault = error_code & PFERR_WRITE_MASK;
int user_fault = error_code & PFERR_USER_MASK;
struct guest_walker walker;
int r;
pfn_t pfn;
int level = PT_PAGE_TABLE_LEVEL;
bool force_pt_level;
unsigned long mmu_seq;
bool map_writable, is_self_change_mapping;
pgprintk("%s: addr %lx err %x\n", __func__, addr, error_code);
if (unlikely(error_code & PFERR_RSVD_MASK)) {
r = handle_mmio_page_fault(vcpu, addr, error_code,
mmu_is_nested(vcpu));
if (likely(r != RET_MMIO_PF_INVALID))
return r;
/*
* page fault with PFEC.RSVD = 1 is caused by shadow
* page fault, should not be used to walk guest page
* table.
*/
error_code &= ~PFERR_RSVD_MASK;
};
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, error_code);
/*
* The page is not mapped by the guest. Let the guest handle it.
*/
if (!r) {
pgprintk("%s: guest page fault\n", __func__);
if (!prefault)
inject_page_fault(vcpu, &walker.fault);
return 0;
}
vcpu->arch.write_fault_to_shadow_pgtable = false;
is_self_change_mapping = FNAME(is_self_change_mapping)(vcpu,
&walker, user_fault, &vcpu->arch.write_fault_to_shadow_pgtable);
if (walker.level >= PT_DIRECTORY_LEVEL && !is_self_change_mapping) {
force_pt_level = mapping_level_dirty_bitmap(vcpu, walker.gfn);
if (!force_pt_level) {
level = min(walker.level, mapping_level(vcpu, walker.gfn));
walker.gfn = walker.gfn & ~(KVM_PAGES_PER_HPAGE(level) - 1);
}
} else
force_pt_level = true;
mmu_seq = vcpu->kvm->mmu_notifier_seq;
smp_rmb();
if (try_async_pf(vcpu, prefault, walker.gfn, addr, &pfn, write_fault,
&map_writable))
return 0;
if (handle_abnormal_pfn(vcpu, mmu_is_nested(vcpu) ? 0 : addr,
walker.gfn, pfn, walker.pte_access, &r))
return r;
/*
* Do not change pte_access if the pfn is a mmio page, otherwise
* we will cache the incorrect access into mmio spte.
*/
if (write_fault && !(walker.pte_access & ACC_WRITE_MASK) &&
!is_write_protection(vcpu) && !user_fault &&
!is_noslot_pfn(pfn)) {
walker.pte_access |= ACC_WRITE_MASK;
walker.pte_access &= ~ACC_USER_MASK;
/*
* If we converted a user page to a kernel page,
* so that the kernel can write to it when cr0.wp=0,
* then we should prevent the kernel from executing it
* if SMEP is enabled.
*/
if (kvm_read_cr4_bits(vcpu, X86_CR4_SMEP))
walker.pte_access &= ~ACC_EXEC_MASK;
}
spin_lock(&vcpu->kvm->mmu_lock);
if (mmu_notifier_retry(vcpu->kvm, mmu_seq))
goto out_unlock;
kvm_mmu_audit(vcpu, AUDIT_PRE_PAGE_FAULT);
make_mmu_pages_available(vcpu);
if (!force_pt_level)
transparent_hugepage_adjust(vcpu, &walker.gfn, &pfn, &level);
r = FNAME(fetch)(vcpu, addr, &walker, write_fault,
level, pfn, map_writable, prefault);
++vcpu->stat.pf_fixed;
kvm_mmu_audit(vcpu, AUDIT_POST_PAGE_FAULT);
spin_unlock(&vcpu->kvm->mmu_lock);
return r;
out_unlock:
spin_unlock(&vcpu->kvm->mmu_lock);
kvm_release_pfn_clean(pfn);
return 0;
}
static gpa_t FNAME(get_level1_sp_gpa)(struct kvm_mmu_page *sp)
{
int offset = 0;
WARN_ON(sp->role.level != PT_PAGE_TABLE_LEVEL);
if (PTTYPE == 32)
offset = sp->role.quadrant << PT64_LEVEL_BITS;
return gfn_to_gpa(sp->gfn) + offset * sizeof(pt_element_t);
}
static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)
{
struct kvm_shadow_walk_iterator iterator;
struct kvm_mmu_page *sp;
int level;
u64 *sptep;
vcpu_clear_mmio_info(vcpu, gva);
/*
* No need to check return value here, rmap_can_add() can
* help us to skip pte prefetch later.
*/
mmu_topup_memory_caches(vcpu);
if (!VALID_PAGE(vcpu->arch.mmu.root_hpa)) {
WARN_ON(1);
return;
}
spin_lock(&vcpu->kvm->mmu_lock);
for_each_shadow_entry(vcpu, gva, iterator) {
level = iterator.level;
sptep = iterator.sptep;
sp = page_header(__pa(sptep));
if (is_last_spte(*sptep, level)) {
pt_element_t gpte;
gpa_t pte_gpa;
if (!sp->unsync)
break;
pte_gpa = FNAME(get_level1_sp_gpa)(sp);
pte_gpa += (sptep - sp->spt) * sizeof(pt_element_t);
if (mmu_page_zap_pte(vcpu->kvm, sp, sptep))
kvm_flush_remote_tlbs(vcpu->kvm);
if (!rmap_can_add(vcpu))
break;
if (kvm_vcpu_read_guest_atomic(vcpu, pte_gpa, &gpte,
sizeof(pt_element_t)))
break;
FNAME(update_pte)(vcpu, sp, sptep, &gpte);
}
if (!is_shadow_present_pte(*sptep) || !sp->unsync_children)
break;
}
spin_unlock(&vcpu->kvm->mmu_lock);
}
static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t vaddr, u32 access,
struct x86_exception *exception)
{
struct guest_walker walker;
gpa_t gpa = UNMAPPED_GVA;
int r;
r = FNAME(walk_addr)(&walker, vcpu, vaddr, access);
if (r) {
gpa = gfn_to_gpa(walker.gfn);
gpa |= vaddr & ~PAGE_MASK;
} else if (exception)
*exception = walker.fault;
return gpa;
}
#if PTTYPE != PTTYPE_EPT
static gpa_t FNAME(gva_to_gpa_nested)(struct kvm_vcpu *vcpu, gva_t vaddr,
u32 access,
struct x86_exception *exception)
{
struct guest_walker walker;
gpa_t gpa = UNMAPPED_GVA;
int r;
r = FNAME(walk_addr_nested)(&walker, vcpu, vaddr, access);
if (r) {
gpa = gfn_to_gpa(walker.gfn);
gpa |= vaddr & ~PAGE_MASK;
} else if (exception)
*exception = walker.fault;
return gpa;
}
#endif
/*
* 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.
*
* Note:
* We should flush all tlbs if spte is dropped even though guest is
* responsible for it. Since if we don't, kvm_mmu_notifier_invalidate_page
* and kvm_mmu_notifier_invalidate_range_start detect the mapping page isn't
* used by guest then tlbs are not flushed, so guest is allowed to access the
* freed pages.
* And we increase kvm->tlbs_dirty to delay tlbs flush in this case.
*/
static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
{
int i, nr_present = 0;
bool host_writable;
gpa_t first_pte_gpa;
/* direct kvm_mmu_page can not be unsync. */
BUG_ON(sp->role.direct);
first_pte_gpa = FNAME(get_level1_sp_gpa)(sp);
for (i = 0; i < PT64_ENT_PER_PAGE; i++) {
unsigned pte_access;
pt_element_t gpte;
gpa_t pte_gpa;
gfn_t gfn;
if (!sp->spt[i])
continue;
pte_gpa = first_pte_gpa + i * sizeof(pt_element_t);
if (kvm_vcpu_read_guest_atomic(vcpu, pte_gpa, &gpte,
sizeof(pt_element_t)))
return -EINVAL;
if (FNAME(prefetch_invalid_gpte)(vcpu, sp, &sp->spt[i], gpte)) {
vcpu->kvm->tlbs_dirty++;
continue;
}
gfn = gpte_to_gfn(gpte);
pte_access = sp->role.access;
pte_access &= FNAME(gpte_access)(vcpu, gpte);
FNAME(protect_clean_gpte)(&pte_access, gpte);
if (sync_mmio_spte(vcpu, &sp->spt[i], gfn, pte_access,
&nr_present))
continue;
if (gfn != sp->gfns[i]) {
drop_spte(vcpu->kvm, &sp->spt[i]);
vcpu->kvm->tlbs_dirty++;
continue;
}
nr_present++;
host_writable = sp->spt[i] & SPTE_HOST_WRITEABLE;
set_spte(vcpu, &sp->spt[i], pte_access,
PT_PAGE_TABLE_LEVEL, gfn,
spte_to_pfn(sp->spt[i]), true, false,
host_writable);
}
return !nr_present;
}
#undef pt_element_t
#undef guest_walker
#undef FNAME
#undef PT_BASE_ADDR_MASK
#undef PT_INDEX
#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
#undef PT_GUEST_ACCESSED_MASK
#undef PT_GUEST_DIRTY_MASK
#undef PT_GUEST_DIRTY_SHIFT
#undef PT_GUEST_ACCESSED_SHIFT
