swh:1:snp:173f8deb0c56c557784b4fd217e7608ac6197844
Tip revision: bfa76d49576599a4b9f9b7a71f23d73d6dcff735 authored by Linus Torvalds on 09 February 2015, 02:54:22 UTC
Linux 3.19
Linux 3.19
Tip revision: bfa76d4
p2m.c
/*
* Xen leaves the responsibility for maintaining p2m mappings to the
* guests themselves, but it must also access and update the p2m array
* during suspend/resume when all the pages are reallocated.
*
* The logical flat p2m table is mapped to a linear kernel memory area.
* For accesses by Xen a three-level tree linked via mfns only is set up to
* allow the address space to be sparse.
*
* Xen
* |
* p2m_top_mfn
* / \
* p2m_mid_mfn p2m_mid_mfn
* / /
* p2m p2m p2m ...
*
* The p2m_mid_mfn pages are mapped by p2m_top_mfn_p.
*
* The p2m_top_mfn level is limited to 1 page, so the maximum representable
* pseudo-physical address space is:
* P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE pages
*
* P2M_PER_PAGE depends on the architecture, as a mfn is always
* unsigned long (8 bytes on 64-bit, 4 bytes on 32), leading to
* 512 and 1024 entries respectively.
*
* In short, these structures contain the Machine Frame Number (MFN) of the PFN.
*
* However not all entries are filled with MFNs. Specifically for all other
* leaf entries, or for the top root, or middle one, for which there is a void
* entry, we assume it is "missing". So (for example)
* pfn_to_mfn(0x90909090)=INVALID_P2M_ENTRY.
* We have a dedicated page p2m_missing with all entries being
* INVALID_P2M_ENTRY. This page may be referenced multiple times in the p2m
* list/tree in case there are multiple areas with P2M_PER_PAGE invalid pfns.
*
* We also have the possibility of setting 1-1 mappings on certain regions, so
* that:
* pfn_to_mfn(0xc0000)=0xc0000
*
* The benefit of this is, that we can assume for non-RAM regions (think
* PCI BARs, or ACPI spaces), we can create mappings easily because we
* get the PFN value to match the MFN.
*
* For this to work efficiently we have one new page p2m_identity. All entries
* in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only
* recognizes that and MFNs, no other fancy value).
*
* On lookup we spot that the entry points to p2m_identity and return the
* identity value instead of dereferencing and returning INVALID_P2M_ENTRY.
* If the entry points to an allocated page, we just proceed as before and
* return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in
* appropriate functions (pfn_to_mfn).
*
* The reason for having the IDENTITY_FRAME_BIT instead of just returning the
* PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a
* non-identity pfn. To protect ourselves against we elect to set (and get) the
* IDENTITY_FRAME_BIT on all identity mapped PFNs.
*/
#include <linux/init.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/hash.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <linux/bootmem.h>
#include <linux/slab.h>
#include <asm/cache.h>
#include <asm/setup.h>
#include <asm/uaccess.h>
#include <asm/xen/page.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>
#include <xen/balloon.h>
#include <xen/grant_table.h>
#include "p2m.h"
#include "multicalls.h"
#include "xen-ops.h"
#define PMDS_PER_MID_PAGE (P2M_MID_PER_PAGE / PTRS_PER_PTE)
static void __init m2p_override_init(void);
unsigned long *xen_p2m_addr __read_mostly;
EXPORT_SYMBOL_GPL(xen_p2m_addr);
unsigned long xen_p2m_size __read_mostly;
EXPORT_SYMBOL_GPL(xen_p2m_size);
unsigned long xen_max_p2m_pfn __read_mostly;
EXPORT_SYMBOL_GPL(xen_max_p2m_pfn);
static DEFINE_SPINLOCK(p2m_update_lock);
static unsigned long *p2m_mid_missing_mfn;
static unsigned long *p2m_top_mfn;
static unsigned long **p2m_top_mfn_p;
static unsigned long *p2m_missing;
static unsigned long *p2m_identity;
static pte_t *p2m_missing_pte;
static pte_t *p2m_identity_pte;
static inline unsigned p2m_top_index(unsigned long pfn)
{
BUG_ON(pfn >= MAX_P2M_PFN);
return pfn / (P2M_MID_PER_PAGE * P2M_PER_PAGE);
}
static inline unsigned p2m_mid_index(unsigned long pfn)
{
return (pfn / P2M_PER_PAGE) % P2M_MID_PER_PAGE;
}
static inline unsigned p2m_index(unsigned long pfn)
{
return pfn % P2M_PER_PAGE;
}
static void p2m_top_mfn_init(unsigned long *top)
{
unsigned i;
for (i = 0; i < P2M_TOP_PER_PAGE; i++)
top[i] = virt_to_mfn(p2m_mid_missing_mfn);
}
static void p2m_top_mfn_p_init(unsigned long **top)
{
unsigned i;
for (i = 0; i < P2M_TOP_PER_PAGE; i++)
top[i] = p2m_mid_missing_mfn;
}
static void p2m_mid_mfn_init(unsigned long *mid, unsigned long *leaf)
{
unsigned i;
for (i = 0; i < P2M_MID_PER_PAGE; i++)
mid[i] = virt_to_mfn(leaf);
}
static void p2m_init(unsigned long *p2m)
{
unsigned i;
for (i = 0; i < P2M_PER_PAGE; i++)
p2m[i] = INVALID_P2M_ENTRY;
}
static void p2m_init_identity(unsigned long *p2m, unsigned long pfn)
{
unsigned i;
for (i = 0; i < P2M_PER_PAGE; i++)
p2m[i] = IDENTITY_FRAME(pfn + i);
}
static void * __ref alloc_p2m_page(void)
{
if (unlikely(!slab_is_available()))
return alloc_bootmem_align(PAGE_SIZE, PAGE_SIZE);
return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT);
}
static void __ref free_p2m_page(void *p)
{
if (unlikely(!slab_is_available())) {
free_bootmem((unsigned long)p, PAGE_SIZE);
return;
}
free_page((unsigned long)p);
}
/*
* Build the parallel p2m_top_mfn and p2m_mid_mfn structures
*
* This is called both at boot time, and after resuming from suspend:
* - At boot time we're called rather early, and must use alloc_bootmem*()
* to allocate memory.
*
* - After resume we're called from within stop_machine, but the mfn
* tree should already be completely allocated.
*/
void __ref xen_build_mfn_list_list(void)
{
unsigned long pfn, mfn;
pte_t *ptep;
unsigned int level, topidx, mididx;
unsigned long *mid_mfn_p;
if (xen_feature(XENFEAT_auto_translated_physmap))
return;
/* Pre-initialize p2m_top_mfn to be completely missing */
if (p2m_top_mfn == NULL) {
p2m_mid_missing_mfn = alloc_p2m_page();
p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
p2m_top_mfn_p = alloc_p2m_page();
p2m_top_mfn_p_init(p2m_top_mfn_p);
p2m_top_mfn = alloc_p2m_page();
p2m_top_mfn_init(p2m_top_mfn);
} else {
/* Reinitialise, mfn's all change after migration */
p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
}
for (pfn = 0; pfn < xen_max_p2m_pfn && pfn < MAX_P2M_PFN;
pfn += P2M_PER_PAGE) {
topidx = p2m_top_index(pfn);
mididx = p2m_mid_index(pfn);
mid_mfn_p = p2m_top_mfn_p[topidx];
ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn),
&level);
BUG_ON(!ptep || level != PG_LEVEL_4K);
mfn = pte_mfn(*ptep);
ptep = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));
/* Don't bother allocating any mfn mid levels if
* they're just missing, just update the stored mfn,
* since all could have changed over a migrate.
*/
if (ptep == p2m_missing_pte || ptep == p2m_identity_pte) {
BUG_ON(mididx);
BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn);
pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE;
continue;
}
if (mid_mfn_p == p2m_mid_missing_mfn) {
mid_mfn_p = alloc_p2m_page();
p2m_mid_mfn_init(mid_mfn_p, p2m_missing);
p2m_top_mfn_p[topidx] = mid_mfn_p;
}
p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
mid_mfn_p[mididx] = mfn;
}
}
void xen_setup_mfn_list_list(void)
{
if (xen_feature(XENFEAT_auto_translated_physmap))
return;
BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);
HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =
virt_to_mfn(p2m_top_mfn);
HYPERVISOR_shared_info->arch.max_pfn = xen_max_p2m_pfn;
}
/* Set up p2m_top to point to the domain-builder provided p2m pages */
void __init xen_build_dynamic_phys_to_machine(void)
{
unsigned long pfn;
if (xen_feature(XENFEAT_auto_translated_physmap))
return;
xen_p2m_addr = (unsigned long *)xen_start_info->mfn_list;
xen_p2m_size = ALIGN(xen_start_info->nr_pages, P2M_PER_PAGE);
for (pfn = xen_start_info->nr_pages; pfn < xen_p2m_size; pfn++)
xen_p2m_addr[pfn] = INVALID_P2M_ENTRY;
xen_max_p2m_pfn = xen_p2m_size;
}
#define P2M_TYPE_IDENTITY 0
#define P2M_TYPE_MISSING 1
#define P2M_TYPE_PFN 2
#define P2M_TYPE_UNKNOWN 3
static int xen_p2m_elem_type(unsigned long pfn)
{
unsigned long mfn;
if (pfn >= xen_p2m_size)
return P2M_TYPE_IDENTITY;
mfn = xen_p2m_addr[pfn];
if (mfn == INVALID_P2M_ENTRY)
return P2M_TYPE_MISSING;
if (mfn & IDENTITY_FRAME_BIT)
return P2M_TYPE_IDENTITY;
return P2M_TYPE_PFN;
}
static void __init xen_rebuild_p2m_list(unsigned long *p2m)
{
unsigned int i, chunk;
unsigned long pfn;
unsigned long *mfns;
pte_t *ptep;
pmd_t *pmdp;
int type;
p2m_missing = alloc_p2m_page();
p2m_init(p2m_missing);
p2m_identity = alloc_p2m_page();
p2m_init(p2m_identity);
p2m_missing_pte = alloc_p2m_page();
paravirt_alloc_pte(&init_mm, __pa(p2m_missing_pte) >> PAGE_SHIFT);
p2m_identity_pte = alloc_p2m_page();
paravirt_alloc_pte(&init_mm, __pa(p2m_identity_pte) >> PAGE_SHIFT);
for (i = 0; i < PTRS_PER_PTE; i++) {
set_pte(p2m_missing_pte + i,
pfn_pte(PFN_DOWN(__pa(p2m_missing)), PAGE_KERNEL_RO));
set_pte(p2m_identity_pte + i,
pfn_pte(PFN_DOWN(__pa(p2m_identity)), PAGE_KERNEL_RO));
}
for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += chunk) {
/*
* Try to map missing/identity PMDs or p2m-pages if possible.
* We have to respect the structure of the mfn_list_list
* which will be built just afterwards.
* Chunk size to test is one p2m page if we are in the middle
* of a mfn_list_list mid page and the complete mid page area
* if we are at index 0 of the mid page. Please note that a
* mid page might cover more than one PMD, e.g. on 32 bit PAE
* kernels.
*/
chunk = (pfn & (P2M_PER_PAGE * P2M_MID_PER_PAGE - 1)) ?
P2M_PER_PAGE : P2M_PER_PAGE * P2M_MID_PER_PAGE;
type = xen_p2m_elem_type(pfn);
i = 0;
if (type != P2M_TYPE_PFN)
for (i = 1; i < chunk; i++)
if (xen_p2m_elem_type(pfn + i) != type)
break;
if (i < chunk)
/* Reset to minimal chunk size. */
chunk = P2M_PER_PAGE;
if (type == P2M_TYPE_PFN || i < chunk) {
/* Use initial p2m page contents. */
#ifdef CONFIG_X86_64
mfns = alloc_p2m_page();
copy_page(mfns, xen_p2m_addr + pfn);
#else
mfns = xen_p2m_addr + pfn;
#endif
ptep = populate_extra_pte((unsigned long)(p2m + pfn));
set_pte(ptep,
pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL));
continue;
}
if (chunk == P2M_PER_PAGE) {
/* Map complete missing or identity p2m-page. */
mfns = (type == P2M_TYPE_MISSING) ?
p2m_missing : p2m_identity;
ptep = populate_extra_pte((unsigned long)(p2m + pfn));
set_pte(ptep,
pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL_RO));
continue;
}
/* Complete missing or identity PMD(s) can be mapped. */
ptep = (type == P2M_TYPE_MISSING) ?
p2m_missing_pte : p2m_identity_pte;
for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
pmdp = populate_extra_pmd(
(unsigned long)(p2m + pfn) + i * PMD_SIZE);
set_pmd(pmdp, __pmd(__pa(ptep) | _KERNPG_TABLE));
}
}
}
void __init xen_vmalloc_p2m_tree(void)
{
static struct vm_struct vm;
vm.flags = VM_ALLOC;
vm.size = ALIGN(sizeof(unsigned long) * xen_max_p2m_pfn,
PMD_SIZE * PMDS_PER_MID_PAGE);
vm_area_register_early(&vm, PMD_SIZE * PMDS_PER_MID_PAGE);
pr_notice("p2m virtual area at %p, size is %lx\n", vm.addr, vm.size);
xen_max_p2m_pfn = vm.size / sizeof(unsigned long);
xen_rebuild_p2m_list(vm.addr);
xen_p2m_addr = vm.addr;
xen_p2m_size = xen_max_p2m_pfn;
xen_inv_extra_mem();
m2p_override_init();
}
unsigned long get_phys_to_machine(unsigned long pfn)
{
pte_t *ptep;
unsigned int level;
if (unlikely(pfn >= xen_p2m_size)) {
if (pfn < xen_max_p2m_pfn)
return xen_chk_extra_mem(pfn);
return IDENTITY_FRAME(pfn);
}
ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);
BUG_ON(!ptep || level != PG_LEVEL_4K);
/*
* The INVALID_P2M_ENTRY is filled in both p2m_*identity
* and in p2m_*missing, so returning the INVALID_P2M_ENTRY
* would be wrong.
*/
if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity)))
return IDENTITY_FRAME(pfn);
return xen_p2m_addr[pfn];
}
EXPORT_SYMBOL_GPL(get_phys_to_machine);
/*
* Allocate new pmd(s). It is checked whether the old pmd is still in place.
* If not, nothing is changed. This is okay as the only reason for allocating
* a new pmd is to replace p2m_missing_pte or p2m_identity_pte by a individual
* pmd. In case of PAE/x86-32 there are multiple pmds to allocate!
*/
static pte_t *alloc_p2m_pmd(unsigned long addr, pte_t *pte_pg)
{
pte_t *ptechk;
pte_t *pte_newpg[PMDS_PER_MID_PAGE];
pmd_t *pmdp;
unsigned int level;
unsigned long flags;
unsigned long vaddr;
int i;
/* Do all allocations first to bail out in error case. */
for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
pte_newpg[i] = alloc_p2m_page();
if (!pte_newpg[i]) {
for (i--; i >= 0; i--)
free_p2m_page(pte_newpg[i]);
return NULL;
}
}
vaddr = addr & ~(PMD_SIZE * PMDS_PER_MID_PAGE - 1);
for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
copy_page(pte_newpg[i], pte_pg);
paravirt_alloc_pte(&init_mm, __pa(pte_newpg[i]) >> PAGE_SHIFT);
pmdp = lookup_pmd_address(vaddr);
BUG_ON(!pmdp);
spin_lock_irqsave(&p2m_update_lock, flags);
ptechk = lookup_address(vaddr, &level);
if (ptechk == pte_pg) {
set_pmd(pmdp,
__pmd(__pa(pte_newpg[i]) | _KERNPG_TABLE));
pte_newpg[i] = NULL;
}
spin_unlock_irqrestore(&p2m_update_lock, flags);
if (pte_newpg[i]) {
paravirt_release_pte(__pa(pte_newpg[i]) >> PAGE_SHIFT);
free_p2m_page(pte_newpg[i]);
}
vaddr += PMD_SIZE;
}
return lookup_address(addr, &level);
}
/*
* Fully allocate the p2m structure for a given pfn. We need to check
* that both the top and mid levels are allocated, and make sure the
* parallel mfn tree is kept in sync. We may race with other cpus, so
* the new pages are installed with cmpxchg; if we lose the race then
* simply free the page we allocated and use the one that's there.
*/
static bool alloc_p2m(unsigned long pfn)
{
unsigned topidx, mididx;
unsigned long *top_mfn_p, *mid_mfn;
pte_t *ptep, *pte_pg;
unsigned int level;
unsigned long flags;
unsigned long addr = (unsigned long)(xen_p2m_addr + pfn);
unsigned long p2m_pfn;
topidx = p2m_top_index(pfn);
mididx = p2m_mid_index(pfn);
ptep = lookup_address(addr, &level);
BUG_ON(!ptep || level != PG_LEVEL_4K);
pte_pg = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));
if (pte_pg == p2m_missing_pte || pte_pg == p2m_identity_pte) {
/* PMD level is missing, allocate a new one */
ptep = alloc_p2m_pmd(addr, pte_pg);
if (!ptep)
return false;
}
if (p2m_top_mfn) {
top_mfn_p = &p2m_top_mfn[topidx];
mid_mfn = ACCESS_ONCE(p2m_top_mfn_p[topidx]);
BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
if (mid_mfn == p2m_mid_missing_mfn) {
/* Separately check the mid mfn level */
unsigned long missing_mfn;
unsigned long mid_mfn_mfn;
unsigned long old_mfn;
mid_mfn = alloc_p2m_page();
if (!mid_mfn)
return false;
p2m_mid_mfn_init(mid_mfn, p2m_missing);
missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
mid_mfn_mfn = virt_to_mfn(mid_mfn);
old_mfn = cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn);
if (old_mfn != missing_mfn) {
free_p2m_page(mid_mfn);
mid_mfn = mfn_to_virt(old_mfn);
} else {
p2m_top_mfn_p[topidx] = mid_mfn;
}
}
} else {
mid_mfn = NULL;
}
p2m_pfn = pte_pfn(ACCESS_ONCE(*ptep));
if (p2m_pfn == PFN_DOWN(__pa(p2m_identity)) ||
p2m_pfn == PFN_DOWN(__pa(p2m_missing))) {
/* p2m leaf page is missing */
unsigned long *p2m;
p2m = alloc_p2m_page();
if (!p2m)
return false;
if (p2m_pfn == PFN_DOWN(__pa(p2m_missing)))
p2m_init(p2m);
else
p2m_init_identity(p2m, pfn);
spin_lock_irqsave(&p2m_update_lock, flags);
if (pte_pfn(*ptep) == p2m_pfn) {
set_pte(ptep,
pfn_pte(PFN_DOWN(__pa(p2m)), PAGE_KERNEL));
if (mid_mfn)
mid_mfn[mididx] = virt_to_mfn(p2m);
p2m = NULL;
}
spin_unlock_irqrestore(&p2m_update_lock, flags);
if (p2m)
free_p2m_page(p2m);
}
return true;
}
unsigned long __init set_phys_range_identity(unsigned long pfn_s,
unsigned long pfn_e)
{
unsigned long pfn;
if (unlikely(pfn_s >= xen_p2m_size))
return 0;
if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
return pfn_e - pfn_s;
if (pfn_s > pfn_e)
return 0;
if (pfn_e > xen_p2m_size)
pfn_e = xen_p2m_size;
for (pfn = pfn_s; pfn < pfn_e; pfn++)
xen_p2m_addr[pfn] = IDENTITY_FRAME(pfn);
return pfn - pfn_s;
}
bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
{
pte_t *ptep;
unsigned int level;
/* don't track P2M changes in autotranslate guests */
if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
return true;
if (unlikely(pfn >= xen_p2m_size)) {
BUG_ON(mfn != INVALID_P2M_ENTRY);
return true;
}
if (likely(!xen_safe_write_ulong(xen_p2m_addr + pfn, mfn)))
return true;
ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);
BUG_ON(!ptep || level != PG_LEVEL_4K);
if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_missing)))
return mfn == INVALID_P2M_ENTRY;
if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity)))
return mfn == IDENTITY_FRAME(pfn);
return false;
}
bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
{
if (unlikely(!__set_phys_to_machine(pfn, mfn))) {
if (!alloc_p2m(pfn))
return false;
return __set_phys_to_machine(pfn, mfn);
}
return true;
}
#define M2P_OVERRIDE_HASH_SHIFT 10
#define M2P_OVERRIDE_HASH (1 << M2P_OVERRIDE_HASH_SHIFT)
static struct list_head *m2p_overrides;
static DEFINE_SPINLOCK(m2p_override_lock);
static void __init m2p_override_init(void)
{
unsigned i;
m2p_overrides = alloc_bootmem_align(
sizeof(*m2p_overrides) * M2P_OVERRIDE_HASH,
sizeof(unsigned long));
for (i = 0; i < M2P_OVERRIDE_HASH; i++)
INIT_LIST_HEAD(&m2p_overrides[i]);
}
static unsigned long mfn_hash(unsigned long mfn)
{
return hash_long(mfn, M2P_OVERRIDE_HASH_SHIFT);
}
/* Add an MFN override for a particular page */
static int m2p_add_override(unsigned long mfn, struct page *page,
struct gnttab_map_grant_ref *kmap_op)
{
unsigned long flags;
unsigned long pfn;
unsigned long uninitialized_var(address);
unsigned level;
pte_t *ptep = NULL;
pfn = page_to_pfn(page);
if (!PageHighMem(page)) {
address = (unsigned long)__va(pfn << PAGE_SHIFT);
ptep = lookup_address(address, &level);
if (WARN(ptep == NULL || level != PG_LEVEL_4K,
"m2p_add_override: pfn %lx not mapped", pfn))
return -EINVAL;
}
if (kmap_op != NULL) {
if (!PageHighMem(page)) {
struct multicall_space mcs =
xen_mc_entry(sizeof(*kmap_op));
MULTI_grant_table_op(mcs.mc,
GNTTABOP_map_grant_ref, kmap_op, 1);
xen_mc_issue(PARAVIRT_LAZY_MMU);
}
}
spin_lock_irqsave(&m2p_override_lock, flags);
list_add(&page->lru, &m2p_overrides[mfn_hash(mfn)]);
spin_unlock_irqrestore(&m2p_override_lock, flags);
/* p2m(m2p(mfn)) == mfn: the mfn is already present somewhere in
* this domain. Set the FOREIGN_FRAME_BIT in the p2m for the other
* pfn so that the following mfn_to_pfn(mfn) calls will return the
* pfn from the m2p_override (the backend pfn) instead.
* We need to do this because the pages shared by the frontend
* (xen-blkfront) can be already locked (lock_page, called by
* do_read_cache_page); when the userspace backend tries to use them
* with direct_IO, mfn_to_pfn returns the pfn of the frontend, so
* do_blockdev_direct_IO is going to try to lock the same pages
* again resulting in a deadlock.
* As a side effect get_user_pages_fast might not be safe on the
* frontend pages while they are being shared with the backend,
* because mfn_to_pfn (that ends up being called by GUPF) will
* return the backend pfn rather than the frontend pfn. */
pfn = mfn_to_pfn_no_overrides(mfn);
if (__pfn_to_mfn(pfn) == mfn)
set_phys_to_machine(pfn, FOREIGN_FRAME(mfn));
return 0;
}
int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
struct gnttab_map_grant_ref *kmap_ops,
struct page **pages, unsigned int count)
{
int i, ret = 0;
bool lazy = false;
pte_t *pte;
if (xen_feature(XENFEAT_auto_translated_physmap))
return 0;
if (kmap_ops &&
!in_interrupt() &&
paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
arch_enter_lazy_mmu_mode();
lazy = true;
}
for (i = 0; i < count; i++) {
unsigned long mfn, pfn;
/* Do not add to override if the map failed. */
if (map_ops[i].status)
continue;
if (map_ops[i].flags & GNTMAP_contains_pte) {
pte = (pte_t *)(mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
(map_ops[i].host_addr & ~PAGE_MASK));
mfn = pte_mfn(*pte);
} else {
mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
}
pfn = page_to_pfn(pages[i]);
WARN_ON(PagePrivate(pages[i]));
SetPagePrivate(pages[i]);
set_page_private(pages[i], mfn);
pages[i]->index = pfn_to_mfn(pfn);
if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) {
ret = -ENOMEM;
goto out;
}
if (kmap_ops) {
ret = m2p_add_override(mfn, pages[i], &kmap_ops[i]);
if (ret)
goto out;
}
}
out:
if (lazy)
arch_leave_lazy_mmu_mode();
return ret;
}
EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);
static struct page *m2p_find_override(unsigned long mfn)
{
unsigned long flags;
struct list_head *bucket;
struct page *p, *ret;
if (unlikely(!m2p_overrides))
return NULL;
ret = NULL;
bucket = &m2p_overrides[mfn_hash(mfn)];
spin_lock_irqsave(&m2p_override_lock, flags);
list_for_each_entry(p, bucket, lru) {
if (page_private(p) == mfn) {
ret = p;
break;
}
}
spin_unlock_irqrestore(&m2p_override_lock, flags);
return ret;
}
static int m2p_remove_override(struct page *page,
struct gnttab_map_grant_ref *kmap_op,
unsigned long mfn)
{
unsigned long flags;
unsigned long pfn;
unsigned long uninitialized_var(address);
unsigned level;
pte_t *ptep = NULL;
pfn = page_to_pfn(page);
if (!PageHighMem(page)) {
address = (unsigned long)__va(pfn << PAGE_SHIFT);
ptep = lookup_address(address, &level);
if (WARN(ptep == NULL || level != PG_LEVEL_4K,
"m2p_remove_override: pfn %lx not mapped", pfn))
return -EINVAL;
}
spin_lock_irqsave(&m2p_override_lock, flags);
list_del(&page->lru);
spin_unlock_irqrestore(&m2p_override_lock, flags);
if (kmap_op != NULL) {
if (!PageHighMem(page)) {
struct multicall_space mcs;
struct gnttab_unmap_and_replace *unmap_op;
struct page *scratch_page = get_balloon_scratch_page();
unsigned long scratch_page_address = (unsigned long)
__va(page_to_pfn(scratch_page) << PAGE_SHIFT);
/*
* It might be that we queued all the m2p grant table
* hypercalls in a multicall, then m2p_remove_override
* get called before the multicall has actually been
* issued. In this case handle is going to -1 because
* it hasn't been modified yet.
*/
if (kmap_op->handle == -1)
xen_mc_flush();
/*
* Now if kmap_op->handle is negative it means that the
* hypercall actually returned an error.
*/
if (kmap_op->handle == GNTST_general_error) {
pr_warn("m2p_remove_override: pfn %lx mfn %lx, failed to modify kernel mappings",
pfn, mfn);
put_balloon_scratch_page();
return -1;
}
xen_mc_batch();
mcs = __xen_mc_entry(
sizeof(struct gnttab_unmap_and_replace));
unmap_op = mcs.args;
unmap_op->host_addr = kmap_op->host_addr;
unmap_op->new_addr = scratch_page_address;
unmap_op->handle = kmap_op->handle;
MULTI_grant_table_op(mcs.mc,
GNTTABOP_unmap_and_replace, unmap_op, 1);
mcs = __xen_mc_entry(0);
MULTI_update_va_mapping(mcs.mc, scratch_page_address,
pfn_pte(page_to_pfn(scratch_page),
PAGE_KERNEL_RO), 0);
xen_mc_issue(PARAVIRT_LAZY_MMU);
kmap_op->host_addr = 0;
put_balloon_scratch_page();
}
}
/* p2m(m2p(mfn)) == FOREIGN_FRAME(mfn): the mfn is already present
* somewhere in this domain, even before being added to the
* m2p_override (see comment above in m2p_add_override).
* If there are no other entries in the m2p_override corresponding
* to this mfn, then remove the FOREIGN_FRAME_BIT from the p2m for
* the original pfn (the one shared by the frontend): the backend
* cannot do any IO on this page anymore because it has been
* unshared. Removing the FOREIGN_FRAME_BIT from the p2m entry of
* the original pfn causes mfn_to_pfn(mfn) to return the frontend
* pfn again. */
mfn &= ~FOREIGN_FRAME_BIT;
pfn = mfn_to_pfn_no_overrides(mfn);
if (__pfn_to_mfn(pfn) == FOREIGN_FRAME(mfn) &&
m2p_find_override(mfn) == NULL)
set_phys_to_machine(pfn, mfn);
return 0;
}
int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
struct gnttab_map_grant_ref *kmap_ops,
struct page **pages, unsigned int count)
{
int i, ret = 0;
bool lazy = false;
if (xen_feature(XENFEAT_auto_translated_physmap))
return 0;
if (kmap_ops &&
!in_interrupt() &&
paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
arch_enter_lazy_mmu_mode();
lazy = true;
}
for (i = 0; i < count; i++) {
unsigned long mfn = __pfn_to_mfn(page_to_pfn(pages[i]));
unsigned long pfn = page_to_pfn(pages[i]);
if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {
ret = -EINVAL;
goto out;
}
set_page_private(pages[i], INVALID_P2M_ENTRY);
WARN_ON(!PagePrivate(pages[i]));
ClearPagePrivate(pages[i]);
set_phys_to_machine(pfn, pages[i]->index);
if (kmap_ops)
ret = m2p_remove_override(pages[i], &kmap_ops[i], mfn);
if (ret)
goto out;
}
out:
if (lazy)
arch_leave_lazy_mmu_mode();
return ret;
}
EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);
unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn)
{
struct page *p = m2p_find_override(mfn);
unsigned long ret = pfn;
if (p)
ret = page_to_pfn(p);
return ret;
}
EXPORT_SYMBOL_GPL(m2p_find_override_pfn);
#ifdef CONFIG_XEN_DEBUG_FS
#include <linux/debugfs.h>
#include "debugfs.h"
static int p2m_dump_show(struct seq_file *m, void *v)
{
static const char * const type_name[] = {
[P2M_TYPE_IDENTITY] = "identity",
[P2M_TYPE_MISSING] = "missing",
[P2M_TYPE_PFN] = "pfn",
[P2M_TYPE_UNKNOWN] = "abnormal"};
unsigned long pfn, first_pfn;
int type, prev_type;
prev_type = xen_p2m_elem_type(0);
first_pfn = 0;
for (pfn = 0; pfn < xen_p2m_size; pfn++) {
type = xen_p2m_elem_type(pfn);
if (type != prev_type) {
seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn,
type_name[prev_type]);
prev_type = type;
first_pfn = pfn;
}
}
seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn,
type_name[prev_type]);
return 0;
}
static int p2m_dump_open(struct inode *inode, struct file *filp)
{
return single_open(filp, p2m_dump_show, NULL);
}
static const struct file_operations p2m_dump_fops = {
.open = p2m_dump_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
static struct dentry *d_mmu_debug;
static int __init xen_p2m_debugfs(void)
{
struct dentry *d_xen = xen_init_debugfs();
if (d_xen == NULL)
return -ENOMEM;
d_mmu_debug = debugfs_create_dir("mmu", d_xen);
debugfs_create_file("p2m", 0600, d_mmu_debug, NULL, &p2m_dump_fops);
return 0;
}
fs_initcall(xen_p2m_debugfs);
#endif /* CONFIG_XEN_DEBUG_FS */