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postcopy: ram_enable_notify to switch on userfault

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Mark the area of RAM as 'userfault'
Start up a fault-thread to handle any userfaults we might receive
from it (to be filled in later)

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Dr. David Alan Gilbert 2015-11-05 18:11:04 +00:00 • committed by Juan Quintela
parent 1caddf8a81
commit f0a227ade4
4 changed files with 87 additions and 0 deletions
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69
migration/postcopy-ram.c
View file

@ -275,6 +275,69 @@ int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
return 0;
}
/*
* Mark the given area of RAM as requiring notification to unwritten areas
* Used as a callback on qemu_ram_foreach_block.
* host_addr: Base of area to mark
* offset: Offset in the whole ram arena
* length: Length of the section
* opaque: MigrationIncomingState pointer
* Returns 0 on success
*/
static int ram_block_enable_notify(const char *block_name, void *host_addr,
ram_addr_t offset, ram_addr_t length,
void *opaque)
{
MigrationIncomingState *mis = opaque;
struct uffdio_register reg_struct;
reg_struct.range.start = (uintptr_t)host_addr;
reg_struct.range.len = length;
reg_struct.mode = UFFDIO_REGISTER_MODE_MISSING;
/* Now tell our userfault_fd that it's responsible for this area */
if (ioctl(mis->userfault_fd, UFFDIO_REGISTER, &reg_struct)) {
error_report("%s userfault register: %s", __func__, strerror(errno));
return -1;
}
return 0;
}
/*
* Handle faults detected by the USERFAULT markings
*/
static void *postcopy_ram_fault_thread(void *opaque)
{
MigrationIncomingState *mis = opaque;
fprintf(stderr, "postcopy_ram_fault_thread\n");
/* TODO: In later patch */
qemu_sem_post(&mis->fault_thread_sem);
while (1) {
/* TODO: In later patch */
}
return NULL;
}
int postcopy_ram_enable_notify(MigrationIncomingState *mis)
{
/* Create the fault handler thread and wait for it to be ready */
qemu_sem_init(&mis->fault_thread_sem, 0);
qemu_thread_create(&mis->fault_thread, "postcopy/fault",
postcopy_ram_fault_thread, mis, QEMU_THREAD_JOINABLE);
qemu_sem_wait(&mis->fault_thread_sem);
qemu_sem_destroy(&mis->fault_thread_sem);
/* Mark so that we get notified of accesses to unwritten areas */
if (qemu_ram_foreach_block(ram_block_enable_notify, mis)) {
return -1;
}
return 0;
}
#else
/* No target OS support, stubs just fail */
bool postcopy_ram_supported_by_host(void)
@ -301,6 +364,12 @@ int postcopy_ram_discard_range(MigrationIncomingState *mis, uint8_t *start,
assert(0);
return -1;
}
int postcopy_ram_enable_notify(MigrationIncomingState *mis)
{
assert(0);
return -1;
}
#endif
/* ------------------------------------------------------------------------- */