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author | David Hildenbrand <david@redhat.com> | 2021-10-11 19:53:45 +0200 |
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committer | Juan Quintela <quintela@redhat.com> | 2021-11-01 22:56:44 +0100 |
commit | f7b9dcfbcf44aa38d132038e9b675ea7e714a570 (patch) | |
tree | 054ad70c834dcbbe0eba870f434849073ad3c17d /migration | |
parent | 7648297d40649bbffb296b2d8f2f388f19868759 (diff) | |
download | qemu-f7b9dcfbcf44aa38d132038e9b675ea7e714a570.zip qemu-f7b9dcfbcf44aa38d132038e9b675ea7e714a570.tar.gz qemu-f7b9dcfbcf44aa38d132038e9b675ea7e714a570.tar.bz2 |
migration/ram: Factor out populating pages readable in ram_block_populate_pages()
Let's factor out prefaulting/populating to make further changes easier to
review and add a comment what we are actually expecting to happen. While at
it, use the actual page size of the ramblock, which defaults to
qemu_real_host_page_size for anonymous memory. Further, rename
ram_block_populate_pages() to ram_block_populate_read() as well, to make
it clearer what we are doing.
In the future, we might want to use MADV_POPULATE_READ to speed up
population.
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Diffstat (limited to 'migration')
-rw-r--r-- | migration/ram.c | 35 |
1 files changed, 22 insertions, 13 deletions
diff --git a/migration/ram.c b/migration/ram.c index 54df5dc..92c7b78 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -1639,26 +1639,35 @@ out: return ret; } +static inline void populate_read_range(RAMBlock *block, ram_addr_t offset, + ram_addr_t size) +{ + /* + * We read one byte of each page; this will preallocate page tables if + * required and populate the shared zeropage on MAP_PRIVATE anonymous memory + * where no page was populated yet. This might require adaption when + * supporting other mappings, like shmem. + */ + for (; offset < size; offset += block->page_size) { + char tmp = *((char *)block->host + offset); + + /* Don't optimize the read out */ + asm volatile("" : "+r" (tmp)); + } +} + /* - * ram_block_populate_pages: populate memory in the RAM block by reading - * an integer from the beginning of each page. + * ram_block_populate_read: preallocate page tables and populate pages in the + * RAM block by reading a byte 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) +static void ram_block_populate_read(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)); - } + populate_read_range(block, 0, block->used_length); } /* @@ -1684,7 +1693,7 @@ void ram_write_tracking_prepare(void) * UFFDIO_WRITEPROTECT_MODE_WP mode setting would silently skip * pages with pte_none() entries in page table. */ - ram_block_populate_pages(block); + ram_block_populate_read(block); } } |