- 根目录:
- arch
- x86
- xen
- 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 p2m table is logically a flat array, but we implement it as a
* three-level tree to allow the address space to be sparse.
*
* Xen
* |
* p2m_top p2m_top_mfn
* / \ / \
* p2m_mid p2m_mid p2m_mid_mfn p2m_mid_mfn
* / \ / \ / /
* p2m p2m p2m p2m p2m p2m p2m ...
*
* The p2m_mid_mfn pages are mapped by p2m_top_mfn_p.
*
* The p2m_top and p2m_top_mfn levels are 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 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 b/c we
* get the PFN value to match the MFN.
*
* For this to work efficiently we have one new page p2m_identity and
* allocate (via reserved_brk) any other pages we need to cover the sides
* (1GB or 4MB boundary violations). 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.
*
* This simplistic diagram is used to explain the more subtle piece of code.
* There is also a digram of the P2M at the end that can help.
* Imagine your E820 looking as so:
*
* 1GB 2GB
* /-------------------+---------\/----\ /----------\ /---+-----\
* | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM |
* \-------------------+---------/\----/ \----------/ \---+-----/
* ^- 1029MB ^- 2001MB
*
* [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100),
* 2048MB = 524288 (0x80000)]
*
* And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB
* is actually not present (would have to kick the balloon driver to put it in).
*
* When we are told to set the PFNs for identity mapping (see patch: "xen/setup:
* Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start
* of the PFN and the end PFN (263424 and 512256 respectively). The first step
* is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page
* covers 512^2 of page estate (1GB) and in case the start or end PFN is not
* aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn
* to end pfn. We reserve_brk top leaf pages if they are missing (means they
* point to p2m_mid_missing).
*
* With the E820 example above, 263424 is not 1GB aligned so we allocate a
* reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000.
* Each entry in the allocate page is "missing" (points to p2m_missing).
*
* Next stage is to determine if we need to do a more granular boundary check
* on the 4MB (or 2MB depending on architecture) off the start and end pfn's.
* We check if the start pfn and end pfn violate that boundary check, and if
* so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer
* granularity of setting which PFNs are missing and which ones are identity.
* In our example 263424 and 512256 both fail the check so we reserve_brk two
* pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing"
* values) and assign them to p2m[1][2] and p2m[1][488] respectively.
*
* At this point we would at minimum reserve_brk one page, but could be up to
* three. Each call to set_phys_range_identity has at maximum a three page
* cost. If we were to query the P2M at this stage, all those entries from
* start PFN through end PFN (so 1029MB -> 2001MB) would return
* INVALID_P2M_ENTRY ("missing").
*
* The next step is to walk from the start pfn to the end pfn setting
* the IDENTITY_FRAME_BIT on each PFN. This is done in set_phys_range_identity.
* If we find that the middle leaf is pointing to p2m_missing we can swap it
* over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this
* point we do not need to worry about boundary aligment (so no need to
* reserve_brk a middle page, figure out which PFNs are "missing" and which
* ones are identity), as that has been done earlier. If we find that the
* middle leaf is not occupied by p2m_identity or p2m_missing, we dereference
* that page (which covers 512 PFNs) and set the appropriate PFN with
* IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we
* set from p2m[1][2][256->511] and p2m[1][488][0->256] with
* IDENTITY_FRAME_BIT set.
*
* All other regions that are void (or not filled) either point to p2m_missing
* (considered missing) or have the default value of INVALID_P2M_ENTRY (also
* considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511]
* contain the INVALID_P2M_ENTRY value and are considered "missing."
*
* This is what the p2m ends up looking (for the E820 above) with this
* fabulous drawing:
*
* p2m /--------------\
* /-----\ | &mfn_list[0],| /-----------------\
* | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. |
* |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] |
* | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] |
* |-----| \ | [p2m_identity]+\\ | .... |
* | 2 |--\ \-------------------->| ... | \\ \----------------/
* |-----| \ \---------------/ \\
* | 3 |\ \ \\ p2m_identity
* |-----| \ \-------------------->/---------------\ /-----------------\
* | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... |
* \-----/ / | [p2m_identity]+-->| ..., ~0 |
* / /---------------\ | .... | \-----------------/
* / | IDENTITY[@0] | /-+-[x], ~0, ~0.. |
* / | IDENTITY[@256]|<----/ \---------------/
* / | ~0, ~0, .... |
* | \---------------/
* |
* p2m_mid_missing p2m_missing
* /-----------------\ /------------\
* | [p2m_missing] +---->| ~0, ~0, ~0 |
* | [p2m_missing] +---->| ..., ~0 |
* \-----------------/ \------------/
*
* where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT)
*/
#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 <asm/cache.h>
#include <asm/setup.h>
#include <asm/xen/page.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>
#include <xen/grant_table.h>
#include "multicalls.h"
#include "xen-ops.h"
static void __init m2p_override_init(void);
unsigned long xen_max_p2m_pfn __read_mostly;
#define P2M_PER_PAGE (PAGE_SIZE / sizeof(unsigned long))
#define P2M_MID_PER_PAGE (PAGE_SIZE / sizeof(unsigned long *))
#define P2M_TOP_PER_PAGE (PAGE_SIZE / sizeof(unsigned long **))
#define MAX_P2M_PFN (P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE)
/* Placeholders for holes in the address space */
static RESERVE_BRK_ARRAY(unsigned long, p2m_missing, P2M_PER_PAGE);
static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_missing, P2M_MID_PER_PAGE);
static RESERVE_BRK_ARRAY(unsigned long, p2m_mid_missing_mfn, P2M_MID_PER_PAGE);
static RESERVE_BRK_ARRAY(unsigned long **, p2m_top, P2M_TOP_PER_PAGE);
static RESERVE_BRK_ARRAY(unsigned long, p2m_top_mfn, P2M_TOP_PER_PAGE);
static RESERVE_BRK_ARRAY(unsigned long *, p2m_top_mfn_p, P2M_TOP_PER_PAGE);
static RESERVE_BRK_ARRAY(unsigned long, p2m_identity, P2M_PER_PAGE);
RESERVE_BRK(p2m_mid, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));
RESERVE_BRK(p2m_mid_mfn, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));
/* We might hit two boundary violations at the start and end, at max each
* boundary violation will require three middle nodes. */
RESERVE_BRK(p2m_mid_identity, PAGE_SIZE * 2 * 3);
/* When we populate back during bootup, the amount of pages can vary. The
* max we have is seen is 395979, but that does not mean it can't be more.
* Some machines can have 3GB I/O holes even. With early_can_reuse_p2m_middle
* it can re-use Xen provided mfn_list array, so we only need to allocate at
* most three P2M top nodes. */
RESERVE_BRK(p2m_populated, PAGE_SIZE * 3);
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_init(unsigned long ***top)
{
unsigned i;
for (i = 0; i < P2M_TOP_PER_PAGE; i++)
top[i] = p2m_mid_missing;
}
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_init(unsigned long **mid)
{
unsigned i;
for (i = 0; i < P2M_MID_PER_PAGE; i++)
mid[i] = p2m_missing;
}
static void p2m_mid_mfn_init(unsigned long *mid)
{
unsigned i;
for (i = 0; i < P2M_MID_PER_PAGE; i++)
mid[i] = virt_to_mfn(p2m_missing);
}
static void p2m_init(unsigned long *p2m)
{
unsigned i;
for (i = 0; i < P2M_MID_PER_PAGE; i++)
p2m[i] = INVALID_P2M_ENTRY;
}
/*
* 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 very early, and must use extend_brk()
* to allocate memory.
*
* - After resume we're called from within stop_machine, but the mfn
* tree should alreay be completely allocated.
*/
void __ref xen_build_mfn_list_list(void)
{
unsigned long pfn;
/* Pre-initialize p2m_top_mfn to be completely missing */
if (p2m_top_mfn == NULL) {
p2m_mid_missing_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_mid_mfn_init(p2m_mid_missing_mfn);
p2m_top_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_top_mfn_p_init(p2m_top_mfn_p);
p2m_top_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_top_mfn_init(p2m_top_mfn);
} else {
/* Reinitialise, mfn's all change after migration */
p2m_mid_mfn_init(p2m_mid_missing_mfn);
}
for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += P2M_PER_PAGE) {
unsigned topidx = p2m_top_index(pfn);
unsigned mididx = p2m_mid_index(pfn);
unsigned long **mid;
unsigned long *mid_mfn_p;
mid = p2m_top[topidx];
mid_mfn_p = p2m_top_mfn_p[topidx];
/* 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 (mid == p2m_mid_missing) {
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) {
/*
* XXX boot-time only! We should never find
* missing parts of the mfn tree after
* runtime. extend_brk() will BUG if we call
* it too late.
*/
mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_mid_mfn_init(mid_mfn_p);
p2m_top_mfn_p[topidx] = mid_mfn_p;
}
p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
mid_mfn_p[mididx] = virt_to_mfn(mid[mididx]);
}
}
void xen_setup_mfn_list_list(void)
{
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 *mfn_list = (unsigned long *)xen_start_info->mfn_list;
unsigned long max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);
unsigned long pfn;
xen_max_p2m_pfn = max_pfn;
p2m_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_init(p2m_missing);
p2m_mid_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_mid_init(p2m_mid_missing);
p2m_top = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_top_init(p2m_top);
p2m_identity = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_init(p2m_identity);
/*
* The domain builder gives us a pre-constructed p2m array in
* mfn_list for all the pages initially given to us, so we just
* need to graft that into our tree structure.
*/
for (pfn = 0; pfn < max_pfn; pfn += P2M_PER_PAGE) {
unsigned topidx = p2m_top_index(pfn);
unsigned mididx = p2m_mid_index(pfn);
if (p2m_top[topidx] == p2m_mid_missing) {
unsigned long **mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_mid_init(mid);
p2m_top[topidx] = mid;
}
/*
* As long as the mfn_list has enough entries to completely
* fill a p2m page, pointing into the array is ok. But if
* not the entries beyond the last pfn will be undefined.
*/
if (unlikely(pfn + P2M_PER_PAGE > max_pfn)) {
unsigned long p2midx;
p2midx = max_pfn % P2M_PER_PAGE;
for ( ; p2midx < P2M_PER_PAGE; p2midx++)
mfn_list[pfn + p2midx] = INVALID_P2M_ENTRY;
}
p2m_top[topidx][mididx] = &mfn_list[pfn];
}
m2p_override_init();
}
#ifdef CONFIG_X86_64
#include <linux/bootmem.h>
unsigned long __init xen_revector_p2m_tree(void)
{
unsigned long va_start;
unsigned long va_end;
unsigned long pfn;
unsigned long pfn_free = 0;
unsigned long *mfn_list = NULL;
unsigned long size;
va_start = xen_start_info->mfn_list;
/*We copy in increments of P2M_PER_PAGE * sizeof(unsigned long),
* so make sure it is rounded up to that */
size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
va_end = va_start + size;
/* If we were revectored already, don't do it again. */
if (va_start <= __START_KERNEL_map && va_start >= __PAGE_OFFSET)
return 0;
mfn_list = alloc_bootmem_align(size, PAGE_SIZE);
if (!mfn_list) {
pr_warn("Could not allocate space for a new P2M tree!\n");
return xen_start_info->mfn_list;
}
/* Fill it out with INVALID_P2M_ENTRY value */
memset(mfn_list, 0xFF, size);
for (pfn = 0; pfn < ALIGN(MAX_DOMAIN_PAGES, P2M_PER_PAGE); pfn += P2M_PER_PAGE) {
unsigned topidx = p2m_top_index(pfn);
unsigned mididx;
unsigned long *mid_p;
if (!p2m_top[topidx])
continue;
if (p2m_top[topidx] == p2m_mid_missing)
continue;
mididx = p2m_mid_index(pfn);
mid_p = p2m_top[topidx][mididx];
if (!mid_p)
continue;
if ((mid_p == p2m_missing) || (mid_p == p2m_identity))
continue;
if ((unsigned long)mid_p == INVALID_P2M_ENTRY)
continue;
/* The old va. Rebase it on mfn_list */
if (mid_p >= (unsigned long *)va_start && mid_p <= (unsigned long *)va_end) {
unsigned long *new;
if (pfn_free > (size / sizeof(unsigned long))) {
WARN(1, "Only allocated for %ld pages, but we want %ld!\n",
size / sizeof(unsigned long), pfn_free);
return 0;
}
new = &mfn_list[pfn_free];
copy_page(new, mid_p);
p2m_top[topidx][mididx] = &mfn_list[pfn_free];
p2m_top_mfn_p[topidx][mididx] = virt_to_mfn(&mfn_list[pfn_free]);
pfn_free += P2M_PER_PAGE;
}
/* This should be the leafs allocated for identity from _brk. */
}
return (unsigned long)mfn_list;
}
#else
unsigned long __init xen_revector_p2m_tree(void)
{
return 0;
}
#endif
unsigned long get_phys_to_machine(unsigned long pfn)
{
unsigned topidx, mididx, idx;
if (unlikely(pfn >= MAX_P2M_PFN))
return INVALID_P2M_ENTRY;
topidx = p2m_top_index(pfn);
mididx = p2m_mid_index(pfn);
idx = p2m_index(pfn);
/*
* The INVALID_P2M_ENTRY is filled in both p2m_*identity
* and in p2m_*missing, so returning the INVALID_P2M_ENTRY
* would be wrong.
*/
if (p2m_top[topidx][mididx] == p2m_identity)
return IDENTITY_FRAME(pfn);
return p2m_top[topidx][mididx][idx];
}
EXPORT_SYMBOL_GPL(get_phys_to_machine);
static void *alloc_p2m_page(void)
{
return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT);
}
static void free_p2m_page(void *p)
{
free_page((unsigned long)p);
}
/*
* 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_p, **mid;
unsigned long *top_mfn_p, *mid_mfn;
topidx = p2m_top_index(pfn);
mididx = p2m_mid_index(pfn);
top_p = &p2m_top[topidx];
mid = *top_p;
if (mid == p2m_mid_missing) {
/* Mid level is missing, allocate a new one */
mid = alloc_p2m_page();
if (!mid)
return false;
p2m_mid_init(mid);
if (cmpxchg(top_p, p2m_mid_missing, mid) != p2m_mid_missing)
free_p2m_page(mid);
}
top_mfn_p = &p2m_top_mfn[topidx];
mid_mfn = 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;
mid_mfn = alloc_p2m_page();
if (!mid_mfn)
return false;
p2m_mid_mfn_init(mid_mfn);
missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
mid_mfn_mfn = virt_to_mfn(mid_mfn);
if (cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn) != missing_mfn)
free_p2m_page(mid_mfn);
else
p2m_top_mfn_p[topidx] = mid_mfn;
}
if (p2m_top[topidx][mididx] == p2m_identity ||
p2m_top[topidx][mididx] == p2m_missing) {
/* p2m leaf page is missing */
unsigned long *p2m;
unsigned long *p2m_orig = p2m_top[topidx][mididx];
p2m = alloc_p2m_page();
if (!p2m)
return false;
p2m_init(p2m);
if (cmpxchg(&mid[mididx], p2m_orig, p2m) != p2m_orig)
free_p2m_page(p2m);
else
mid_mfn[mididx] = virt_to_mfn(p2m);
}
return true;
}
static bool __init early_alloc_p2m_middle(unsigned long pfn, bool check_boundary)
{
unsigned topidx, mididx, idx;
unsigned long *p2m;
unsigned long *mid_mfn_p;
topidx = p2m_top_index(pfn);
mididx = p2m_mid_index(pfn);
idx = p2m_index(pfn);
/* Pfff.. No boundary cross-over, lets get out. */
if (!idx && check_boundary)
return false;
WARN(p2m_top[topidx][mididx] == p2m_identity,
"P2M[%d][%d] == IDENTITY, should be MISSING (or alloced)!\n",
topidx, mididx);
/*
* Could be done by xen_build_dynamic_phys_to_machine..
*/
if (p2m_top[topidx][mididx] != p2m_missing)
return false;
/* Boundary cross-over for the edges: */
p2m = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_init(p2m);
p2m_top[topidx][mididx] = p2m;
/* For save/restore we need to MFN of the P2M saved */
mid_mfn_p = p2m_top_mfn_p[topidx];
WARN(mid_mfn_p[mididx] != virt_to_mfn(p2m_missing),
"P2M_TOP_P[%d][%d] != MFN of p2m_missing!\n",
topidx, mididx);
mid_mfn_p[mididx] = virt_to_mfn(p2m);
return true;
}
static bool __init early_alloc_p2m(unsigned long pfn)
{
unsigned topidx = p2m_top_index(pfn);
unsigned long *mid_mfn_p;
unsigned long **mid;
mid = p2m_top[topidx];
mid_mfn_p = p2m_top_mfn_p[topidx];
if (mid == p2m_mid_missing) {
mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_mid_init(mid);
p2m_top[topidx] = mid;
BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
}
/* And the save/restore P2M tables.. */
if (mid_mfn_p == p2m_mid_missing_mfn) {
mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_mid_mfn_init(mid_mfn_p);
p2m_top_mfn_p[topidx] = mid_mfn_p;
p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
/* Note: we don't set mid_mfn_p[midix] here,
* look in early_alloc_p2m_middle */
}
return true;
}
/*
* Skim over the P2M tree looking at pages that are either filled with
* INVALID_P2M_ENTRY or with 1:1 PFNs. If found, re-use that page and
* replace the P2M leaf with a p2m_missing or p2m_identity.
* Stick the old page in the new P2M tree location.
*/
bool __init early_can_reuse_p2m_middle(unsigned long set_pfn, unsigned long set_mfn)
{
unsigned topidx;
unsigned mididx;
unsigned ident_pfns;
unsigned inv_pfns;
unsigned long *p2m;
unsigned long *mid_mfn_p;
unsigned idx;
unsigned long pfn;
/* We only look when this entails a P2M middle layer */
if (p2m_index(set_pfn))
return false;
for (pfn = 0; pfn < MAX_DOMAIN_PAGES; pfn += P2M_PER_PAGE) {
topidx = p2m_top_index(pfn);
if (!p2m_top[topidx])
continue;
if (p2m_top[topidx] == p2m_mid_missing)
continue;
mididx = p2m_mid_index(pfn);
p2m = p2m_top[topidx][mididx];
if (!p2m)
continue;
if ((p2m == p2m_missing) || (p2m == p2m_identity))
continue;
if ((unsigned long)p2m == INVALID_P2M_ENTRY)
continue;
ident_pfns = 0;
inv_pfns = 0;
for (idx = 0; idx < P2M_PER_PAGE; idx++) {
/* IDENTITY_PFNs are 1:1 */
if (p2m[idx] == IDENTITY_FRAME(pfn + idx))
ident_pfns++;
else if (p2m[idx] == INVALID_P2M_ENTRY)
inv_pfns++;
else
break;
}
if ((ident_pfns == P2M_PER_PAGE) || (inv_pfns == P2M_PER_PAGE))
goto found;
}
return false;
found:
/* Found one, replace old with p2m_identity or p2m_missing */
p2m_top[topidx][mididx] = (ident_pfns ? p2m_identity : p2m_missing);
/* And the other for save/restore.. */
mid_mfn_p = p2m_top_mfn_p[topidx];
/* NOTE: Even if it is a p2m_identity it should still be point to
* a page filled with INVALID_P2M_ENTRY entries. */
mid_mfn_p[mididx] = virt_to_mfn(p2m_missing);
/* Reset where we want to stick the old page in. */
topidx = p2m_top_index(set_pfn);
mididx = p2m_mid_index(set_pfn);
/* This shouldn't happen */
if (WARN_ON(p2m_top[topidx] == p2m_mid_missing))
early_alloc_p2m(set_pfn);
if (WARN_ON(p2m_top[topidx][mididx] != p2m_missing))
return false;
p2m_init(p2m);
p2m_top[topidx][mididx] = p2m;
mid_mfn_p = p2m_top_mfn_p[topidx];
mid_mfn_p[mididx] = virt_to_mfn(p2m);
return true;
}
bool __init early_set_phys_to_machine(unsigned long pfn, unsigned long mfn)
{
if (unlikely(!__set_phys_to_machine(pfn, mfn))) {
if (!early_alloc_p2m(pfn))
return false;
if (early_can_reuse_p2m_middle(pfn, mfn))
return __set_phys_to_machine(pfn, mfn);
if (!early_alloc_p2m_middle(pfn, false /* boundary crossover OK!*/))
return false;
if (!__set_phys_to_machine(pfn, mfn))
return false;
}
return true;
}
unsigned long __init set_phys_range_identity(unsigned long pfn_s,
unsigned long pfn_e)
{
unsigned long pfn;
if (unlikely(pfn_s >= MAX_P2M_PFN || pfn_e >= MAX_P2M_PFN))
return 0;
if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
return pfn_e - pfn_s;
if (pfn_s > pfn_e)
return 0;
for (pfn = (pfn_s & ~(P2M_MID_PER_PAGE * P2M_PER_PAGE - 1));
pfn < ALIGN(pfn_e, (P2M_MID_PER_PAGE * P2M_PER_PAGE));
pfn += P2M_MID_PER_PAGE * P2M_PER_PAGE)
{
WARN_ON(!early_alloc_p2m(pfn));
}
early_alloc_p2m_middle(pfn_s, true);
early_alloc_p2m_middle(pfn_e, true);
for (pfn = pfn_s; pfn < pfn_e; pfn++)
if (!__set_phys_to_machine(pfn, IDENTITY_FRAME(pfn)))
break;
if (!WARN((pfn - pfn_s) != (pfn_e - pfn_s),
"Identity mapping failed. We are %ld short of 1-1 mappings!\n",
(pfn_e - pfn_s) - (pfn - pfn_s)))
printk(KERN_DEBUG "1-1 mapping on %lx->%lx\n", pfn_s, pfn);
return pfn - pfn_s;
}
/* Try to install p2m mapping; fail if intermediate bits missing */
bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
{
unsigned topidx, mididx, idx;
if (unlikely(xen_feature(XENFEAT_auto_translated_physmap))) {
BUG_ON(pfn != mfn && mfn != INVALID_P2M_ENTRY);
return true;
}
if (unlikely(pfn >= MAX_P2M_PFN)) {
BUG_ON(mfn != INVALID_P2M_ENTRY);
return true;
}
topidx = p2m_top_index(pfn);
mididx = p2m_mid_index(pfn);
idx = p2m_index(pfn);
/* For sparse holes were the p2m leaf has real PFN along with
* PCI holes, stick in the PFN as the MFN value.
*/
if (mfn != INVALID_P2M_ENTRY && (mfn & IDENTITY_FRAME_BIT)) {
if (p2m_top[topidx][mididx] == p2m_identity)
return true;
/* Swap over from MISSING to IDENTITY if needed. */
if (p2m_top[topidx][mididx] == p2m_missing) {
WARN_ON(cmpxchg(&p2m_top[topidx][mididx], p2m_missing,
p2m_identity) != p2m_missing);
return true;
}
}
if (p2m_top[topidx][mididx] == p2m_missing)
return mfn == INVALID_P2M_ENTRY;
p2m_top[topidx][mididx][idx] = mfn;
return true;
}
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;
if (!__set_phys_to_machine(pfn, mfn))
return false;
}
return true;
}
#define M2P_OVERRIDE_HASH_SHIFT 10
#define M2P_OVERRIDE_HASH (1 << M2P_OVERRIDE_HASH_SHIFT)
static RESERVE_BRK_ARRAY(struct list_head, m2p_overrides, M2P_OVERRIDE_HASH);
static DEFINE_SPINLOCK(m2p_override_lock);
static void __init m2p_override_init(void)
{
unsigned i;
m2p_overrides = extend_brk(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 */
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;
int ret = 0;
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;
}
WARN_ON(PagePrivate(page));
SetPagePrivate(page);
set_page_private(page, mfn);
page->index = pfn_to_mfn(pfn);
if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn))))
return -ENOMEM;
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. */
ret = __get_user(pfn, &machine_to_phys_mapping[mfn]);
if (ret == 0 && get_phys_to_machine(pfn) == mfn)
set_phys_to_machine(pfn, FOREIGN_FRAME(mfn));
return 0;
}
EXPORT_SYMBOL_GPL(m2p_add_override);
int m2p_remove_override(struct page *page,
struct gnttab_map_grant_ref *kmap_op)
{
unsigned long flags;
unsigned long mfn;
unsigned long pfn;
unsigned long uninitialized_var(address);
unsigned level;
pte_t *ptep = NULL;
int ret = 0;
pfn = page_to_pfn(page);
mfn = get_phys_to_machine(pfn);
if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT))
return -EINVAL;
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);
WARN_ON(!PagePrivate(page));
ClearPagePrivate(page);
set_phys_to_machine(pfn, page->index);
if (kmap_op != NULL) {
if (!PageHighMem(page)) {
struct multicall_space mcs;
struct gnttab_unmap_grant_ref *unmap_op;
/*
* 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) {
printk(KERN_WARNING "m2p_remove_override: "
"pfn %lx mfn %lx, failed to modify kernel mappings",
pfn, mfn);
return -1;
}
mcs = xen_mc_entry(
sizeof(struct gnttab_unmap_grant_ref));
unmap_op = mcs.args;
unmap_op->host_addr = kmap_op->host_addr;
unmap_op->handle = kmap_op->handle;
unmap_op->dev_bus_addr = 0;
MULTI_grant_table_op(mcs.mc,
GNTTABOP_unmap_grant_ref, unmap_op, 1);
xen_mc_issue(PARAVIRT_LAZY_MMU);
set_pte_at(&init_mm, address, ptep,
pfn_pte(pfn, PAGE_KERNEL));
__flush_tlb_single(address);
kmap_op->host_addr = 0;
}
}
/* 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;
ret = __get_user(pfn, &machine_to_phys_mapping[mfn]);
if (ret == 0 && get_phys_to_machine(pfn) == FOREIGN_FRAME(mfn) &&
m2p_find_override(mfn) == NULL)
set_phys_to_machine(pfn, mfn);
return 0;
}
EXPORT_SYMBOL_GPL(m2p_remove_override);
struct page *m2p_find_override(unsigned long mfn)
{
unsigned long flags;
struct list_head *bucket = &m2p_overrides[mfn_hash(mfn)];
struct page *p, *ret;
ret = NULL;
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;
}
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 level_name[] = { "top", "middle",
"entry", "abnormal", "error"};
#define TYPE_IDENTITY 0
#define TYPE_MISSING 1
#define TYPE_PFN 2
#define TYPE_UNKNOWN 3
static const char * const type_name[] = {
[TYPE_IDENTITY] = "identity",
[TYPE_MISSING] = "missing",
[TYPE_PFN] = "pfn",
[TYPE_UNKNOWN] = "abnormal"};
unsigned long pfn, prev_pfn_type = 0, prev_pfn_level = 0;
unsigned int uninitialized_var(prev_level);
unsigned int uninitialized_var(prev_type);
if (!p2m_top)
return 0;
for (pfn = 0; pfn < MAX_DOMAIN_PAGES; pfn++) {
unsigned topidx = p2m_top_index(pfn);
unsigned mididx = p2m_mid_index(pfn);
unsigned idx = p2m_index(pfn);
unsigned lvl, type;
lvl = 4;
type = TYPE_UNKNOWN;
if (p2m_top[topidx] == p2m_mid_missing) {
lvl = 0; type = TYPE_MISSING;
} else if (p2m_top[topidx] == NULL) {
lvl = 0; type = TYPE_UNKNOWN;
} else if (p2m_top[topidx][mididx] == NULL) {
lvl = 1; type = TYPE_UNKNOWN;
} else if (p2m_top[topidx][mididx] == p2m_identity) {
lvl = 1; type = TYPE_IDENTITY;
} else if (p2m_top[topidx][mididx] == p2m_missing) {
lvl = 1; type = TYPE_MISSING;
} else if (p2m_top[topidx][mididx][idx] == 0) {
lvl = 2; type = TYPE_UNKNOWN;
} else if (p2m_top[topidx][mididx][idx] == IDENTITY_FRAME(pfn)) {
lvl = 2; type = TYPE_IDENTITY;
} else if (p2m_top[topidx][mididx][idx] == INVALID_P2M_ENTRY) {
lvl = 2; type = TYPE_MISSING;
} else if (p2m_top[topidx][mididx][idx] == pfn) {
lvl = 2; type = TYPE_PFN;
} else if (p2m_top[topidx][mididx][idx] != pfn) {
lvl = 2; type = TYPE_PFN;
}
if (pfn == 0) {
prev_level = lvl;
prev_type = type;
}
if (pfn == MAX_DOMAIN_PAGES-1) {
lvl = 3;
type = TYPE_UNKNOWN;
}
if (prev_type != type) {
seq_printf(m, " [0x%lx->0x%lx] %s\n",
prev_pfn_type, pfn, type_name[prev_type]);
prev_pfn_type = pfn;
prev_type = type;
}
if (prev_level != lvl) {
seq_printf(m, " [0x%lx->0x%lx] level %s\n",
prev_pfn_level, pfn, level_name[prev_level]);
prev_pfn_level = pfn;
prev_level = lvl;
}
}
return 0;
#undef TYPE_IDENTITY
#undef TYPE_MISSING
#undef TYPE_PFN
#undef TYPE_UNKNOWN
}
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 */