postcopy_ram.c: place_page and helpers

postcopy_place_page (etc) provide a way for postcopy to place a page
into guests memory atomically (using the copy ioctl on the ufd).

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Dr. David Alan Gilbert 2015-11-05 18:11:10 +00:00 committed by Juan Quintela
parent a82d593b61
commit 696ed9a9b3
4 changed files with 124 additions and 0 deletions

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@ -96,6 +96,7 @@ struct MigrationIncomingState {
int userfault_fd;
QEMUFile *to_src_file;
QemuMutex rp_mutex; /* We send replies from multiple threads */
void *postcopy_tmp_page;
/* See savevm.c */
LoadStateEntry_Head loadvm_handlers;

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@ -69,4 +69,25 @@ void postcopy_discard_send_range(MigrationState *ms, PostcopyDiscardState *pds,
void postcopy_discard_send_finish(MigrationState *ms,
PostcopyDiscardState *pds);
/*
* Place a page (from) at (host) efficiently
* There are restrictions on how 'from' must be mapped, in general best
* to use other postcopy_ routines to allocate.
* returns 0 on success
*/
int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from);
/*
* Place a zero page at (host) atomically
* returns 0 on success
*/
int postcopy_place_page_zero(MigrationIncomingState *mis, void *host);
/*
* Allocate a page of memory that can be mapped at a later point in time
* using postcopy_place_page
* Returns: Pointer to allocated page
*/
void *postcopy_get_tmp_page(MigrationIncomingState *mis);
#endif

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@ -272,6 +272,10 @@ int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
return -1;
}
if (mis->postcopy_tmp_page) {
munmap(mis->postcopy_tmp_page, getpagesize());
mis->postcopy_tmp_page = NULL;
}
return 0;
}
@ -338,6 +342,83 @@ int postcopy_ram_enable_notify(MigrationIncomingState *mis)
return 0;
}
/*
* Place a host page (from) at (host) atomically
* returns 0 on success
*/
int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from)
{
struct uffdio_copy copy_struct;
copy_struct.dst = (uint64_t)(uintptr_t)host;
copy_struct.src = (uint64_t)(uintptr_t)from;
copy_struct.len = getpagesize();
copy_struct.mode = 0;
/* copy also acks to the kernel waking the stalled thread up
* TODO: We can inhibit that ack and only do it if it was requested
* which would be slightly cheaper, but we'd have to be careful
* of the order of updating our page state.
*/
if (ioctl(mis->userfault_fd, UFFDIO_COPY, &copy_struct)) {
int e = errno;
error_report("%s: %s copy host: %p from: %p",
__func__, strerror(e), host, from);
return -e;
}
trace_postcopy_place_page(host);
return 0;
}
/*
* Place a zero page at (host) atomically
* returns 0 on success
*/
int postcopy_place_page_zero(MigrationIncomingState *mis, void *host)
{
struct uffdio_zeropage zero_struct;
zero_struct.range.start = (uint64_t)(uintptr_t)host;
zero_struct.range.len = getpagesize();
zero_struct.mode = 0;
if (ioctl(mis->userfault_fd, UFFDIO_ZEROPAGE, &zero_struct)) {
int e = errno;
error_report("%s: %s zero host: %p",
__func__, strerror(e), host);
return -e;
}
trace_postcopy_place_page_zero(host);
return 0;
}
/*
* Returns a target page of memory that can be mapped at a later point in time
* using postcopy_place_page
* The same address is used repeatedly, postcopy_place_page just takes the
* backing page away.
* Returns: Pointer to allocated page
*
*/
void *postcopy_get_tmp_page(MigrationIncomingState *mis)
{
if (!mis->postcopy_tmp_page) {
mis->postcopy_tmp_page = mmap(NULL, getpagesize(),
PROT_READ | PROT_WRITE, MAP_PRIVATE |
MAP_ANONYMOUS, -1, 0);
if (!mis->postcopy_tmp_page) {
error_report("%s: %s", __func__, strerror(errno));
return NULL;
}
}
return mis->postcopy_tmp_page;
}
#else
/* No target OS support, stubs just fail */
bool postcopy_ram_supported_by_host(void)
@ -370,6 +451,25 @@ int postcopy_ram_enable_notify(MigrationIncomingState *mis)
assert(0);
return -1;
}
int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from)
{
assert(0);
return -1;
}
int postcopy_place_page_zero(MigrationIncomingState *mis, void *host)
{
assert(0);
return -1;
}
void *postcopy_get_tmp_page(MigrationIncomingState *mis)
{
assert(0);
return NULL;
}
#endif
/* ------------------------------------------------------------------------- */

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@ -1551,6 +1551,8 @@ postcopy_discard_send_range(const char *ramblock, unsigned long start, unsigned
postcopy_ram_discard_range(void *start, size_t length) "%p,+%zx"
postcopy_cleanup_range(const char *ramblock, void *host_addr, size_t offset, size_t length) "%s: %p offset=%zx length=%zx"
postcopy_init_range(const char *ramblock, void *host_addr, size_t offset, size_t length) "%s: %p offset=%zx length=%zx"
postcopy_place_page(void *host_addr) "host=%p"
postcopy_place_page_zero(void *host_addr) "host=%p"
# kvm-all.c
kvm_ioctl(int type, void *arg) "type 0x%x, arg %p"