diff options
Diffstat (limited to 'migration/ram.c')
| -rw-r--r-- | migration/ram.c | 119 |
1 files changed, 85 insertions, 34 deletions
diff --git a/migration/ram.c b/migration/ram.c index 40e78952ad..4682f3625c 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -1455,7 +1455,7 @@ static RAMBlock *poll_fault_page(RAMState *rs, ram_addr_t *offset) { struct uffd_msg uffd_msg; void *page_address; - RAMBlock *bs; + RAMBlock *block; int res; if (!migrate_background_snapshot()) { @@ -1468,9 +1468,9 @@ static RAMBlock *poll_fault_page(RAMState *rs, ram_addr_t *offset) } page_address = (void *)(uintptr_t) uffd_msg.arg.pagefault.address; - bs = qemu_ram_block_from_host(page_address, false, offset); - assert(bs && (bs->flags & RAM_UF_WRITEPROTECT) != 0); - return bs; + block = qemu_ram_block_from_host(page_address, false, offset); + assert(block && (block->flags & RAM_UF_WRITEPROTECT) != 0); + return block; } /** @@ -1526,7 +1526,7 @@ bool ram_write_tracking_compatible(void) { const uint64_t uffd_ioctls_mask = BIT(_UFFDIO_WRITEPROTECT); int uffd_fd; - RAMBlock *bs; + RAMBlock *block; bool ret = false; /* Open UFFD file descriptor */ @@ -1537,15 +1537,15 @@ bool ram_write_tracking_compatible(void) RCU_READ_LOCK_GUARD(); - RAMBLOCK_FOREACH_NOT_IGNORED(bs) { + RAMBLOCK_FOREACH_NOT_IGNORED(block) { uint64_t uffd_ioctls; /* Nothing to do with read-only and MMIO-writable regions */ - if (bs->mr->readonly || bs->mr->rom_device) { + if (block->mr->readonly || block->mr->rom_device) { continue; } /* Try to register block memory via UFFD-IO to track writes */ - if (uffd_register_memory(uffd_fd, bs->host, bs->max_length, + if (uffd_register_memory(uffd_fd, block->host, block->max_length, UFFDIO_REGISTER_MODE_WP, &uffd_ioctls)) { goto out; } @@ -1561,6 +1561,55 @@ out: } /* + * ram_block_populate_pages: populate memory in the RAM block by reading + * an integer from the beginning of each page. + * + * Since it's solely used for userfault_fd WP feature, here we just + * hardcode page size to qemu_real_host_page_size. + * + * @block: RAM block to populate + */ +static void ram_block_populate_pages(RAMBlock *block) +{ + char *ptr = (char *) block->host; + + for (ram_addr_t offset = 0; offset < block->used_length; + offset += qemu_real_host_page_size) { + char tmp = *(ptr + offset); + + /* Don't optimize the read out */ + asm volatile("" : "+r" (tmp)); + } +} + +/* + * ram_write_tracking_prepare: prepare for UFFD-WP memory tracking + */ +void ram_write_tracking_prepare(void) +{ + RAMBlock *block; + + RCU_READ_LOCK_GUARD(); + + RAMBLOCK_FOREACH_NOT_IGNORED(block) { + /* Nothing to do with read-only and MMIO-writable regions */ + if (block->mr->readonly || block->mr->rom_device) { + continue; + } + + /* + * Populate pages of the RAM block before enabling userfault_fd + * write protection. + * + * This stage is required since ioctl(UFFDIO_WRITEPROTECT) with + * UFFDIO_WRITEPROTECT_MODE_WP mode setting would silently skip + * pages with pte_none() entries in page table. + */ + ram_block_populate_pages(block); + } +} + +/* * ram_write_tracking_start: start UFFD-WP memory tracking * * Returns 0 for success or negative value in case of error @@ -1569,7 +1618,7 @@ int ram_write_tracking_start(void) { int uffd_fd; RAMState *rs = ram_state; - RAMBlock *bs; + RAMBlock *block; /* Open UFFD file descriptor */ uffd_fd = uffd_create_fd(UFFD_FEATURE_PAGEFAULT_FLAG_WP, true); @@ -1580,27 +1629,27 @@ int ram_write_tracking_start(void) RCU_READ_LOCK_GUARD(); - RAMBLOCK_FOREACH_NOT_IGNORED(bs) { + RAMBLOCK_FOREACH_NOT_IGNORED(block) { /* Nothing to do with read-only and MMIO-writable regions */ - if (bs->mr->readonly || bs->mr->rom_device) { + if (block->mr->readonly || block->mr->rom_device) { continue; } /* Register block memory with UFFD to track writes */ - if (uffd_register_memory(rs->uffdio_fd, bs->host, - bs->max_length, UFFDIO_REGISTER_MODE_WP, NULL)) { + if (uffd_register_memory(rs->uffdio_fd, block->host, + block->max_length, UFFDIO_REGISTER_MODE_WP, NULL)) { goto fail; } /* Apply UFFD write protection to the block memory range */ - if (uffd_change_protection(rs->uffdio_fd, bs->host, - bs->max_length, true, false)) { + if (uffd_change_protection(rs->uffdio_fd, block->host, + block->max_length, true, false)) { goto fail; } - bs->flags |= RAM_UF_WRITEPROTECT; - memory_region_ref(bs->mr); + block->flags |= RAM_UF_WRITEPROTECT; + memory_region_ref(block->mr); - trace_ram_write_tracking_ramblock_start(bs->idstr, bs->page_size, - bs->host, bs->max_length); + trace_ram_write_tracking_ramblock_start(block->idstr, block->page_size, + block->host, block->max_length); } return 0; @@ -1608,19 +1657,20 @@ int ram_write_tracking_start(void) fail: error_report("ram_write_tracking_start() failed: restoring initial memory state"); - RAMBLOCK_FOREACH_NOT_IGNORED(bs) { - if ((bs->flags & RAM_UF_WRITEPROTECT) == 0) { + RAMBLOCK_FOREACH_NOT_IGNORED(block) { + if ((block->flags & RAM_UF_WRITEPROTECT) == 0) { continue; } /* * In case some memory block failed to be write-protected * remove protection and unregister all succeeded RAM blocks */ - uffd_change_protection(rs->uffdio_fd, bs->host, bs->max_length, false, false); - uffd_unregister_memory(rs->uffdio_fd, bs->host, bs->max_length); + uffd_change_protection(rs->uffdio_fd, block->host, block->max_length, + false, false); + uffd_unregister_memory(rs->uffdio_fd, block->host, block->max_length); /* Cleanup flags and remove reference */ - bs->flags &= ~RAM_UF_WRITEPROTECT; - memory_region_unref(bs->mr); + block->flags &= ~RAM_UF_WRITEPROTECT; + memory_region_unref(block->mr); } uffd_close_fd(uffd_fd); @@ -1634,24 +1684,25 @@ fail: void ram_write_tracking_stop(void) { RAMState *rs = ram_state; - RAMBlock *bs; + RAMBlock *block; RCU_READ_LOCK_GUARD(); - RAMBLOCK_FOREACH_NOT_IGNORED(bs) { - if ((bs->flags & RAM_UF_WRITEPROTECT) == 0) { + RAMBLOCK_FOREACH_NOT_IGNORED(block) { + if ((block->flags & RAM_UF_WRITEPROTECT) == 0) { continue; } /* Remove protection and unregister all affected RAM blocks */ - uffd_change_protection(rs->uffdio_fd, bs->host, bs->max_length, false, false); - uffd_unregister_memory(rs->uffdio_fd, bs->host, bs->max_length); + uffd_change_protection(rs->uffdio_fd, block->host, block->max_length, + false, false); + uffd_unregister_memory(rs->uffdio_fd, block->host, block->max_length); - trace_ram_write_tracking_ramblock_stop(bs->idstr, bs->page_size, - bs->host, bs->max_length); + trace_ram_write_tracking_ramblock_stop(block->idstr, block->page_size, + block->host, block->max_length); /* Cleanup flags and remove reference */ - bs->flags &= ~RAM_UF_WRITEPROTECT; - memory_region_unref(bs->mr); + block->flags &= ~RAM_UF_WRITEPROTECT; + memory_region_unref(block->mr); } /* Finally close UFFD file descriptor */ |