From f0a227ade4b0331c9e12fc01f8b74e2531fd496d Mon Sep 17 00:00:00 2001 From: "Dr. David Alan Gilbert" Date: Thu, 5 Nov 2015 18:11:04 +0000 Subject: postcopy: ram_enable_notify to switch on userfault 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 Reviewed-by: David Gibson Reviewed-by: Juan Quintela Reviewed-by: Amit Shah Signed-off-by: Juan Quintela --- migration/postcopy-ram.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++ migration/savevm.c | 9 +++++++ 2 files changed, 78 insertions(+) (limited to 'migration') diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c index 8478bfd..3110b2a 100644 --- a/migration/postcopy-ram.c +++ b/migration/postcopy-ram.c @@ -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, ®_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 /* ------------------------------------------------------------------------- */ diff --git a/migration/savevm.c b/migration/savevm.c index 674f0fb..a7210a2 100644 --- a/migration/savevm.c +++ b/migration/savevm.c @@ -1381,6 +1381,15 @@ static int loadvm_postcopy_handle_listen(MigrationIncomingState *mis) return -1; } + /* + * Sensitise RAM - can now generate requests for blocks that don't exist + * However, at this point the CPU shouldn't be running, and the IO + * shouldn't be doing anything yet so don't actually expect requests + */ + if (postcopy_ram_enable_notify(mis)) { + return -1; + } + /* TODO start up the postcopy listening thread */ return 0; } -- cgit v1.1