diff options
Diffstat (limited to 'exec.c')
| -rw-r--r-- | exec.c | 60 |
1 files changed, 46 insertions, 14 deletions
@@ -3721,6 +3721,7 @@ int ram_block_discard_range(RAMBlock *rb, uint64_t start, size_t length) } if ((start + length) <= rb->used_length) { + bool need_madvise, need_fallocate; uint8_t *host_endaddr = host_startaddr + length; if ((uintptr_t)host_endaddr & (rb->page_size - 1)) { error_report("ram_block_discard_range: Unaligned end address: %p", @@ -3730,29 +3731,60 @@ int ram_block_discard_range(RAMBlock *rb, uint64_t start, size_t length) errno = ENOTSUP; /* If we are missing MADVISE etc */ - if (rb->page_size == qemu_host_page_size) { -#if defined(CONFIG_MADVISE) - /* Note: We need the madvise MADV_DONTNEED behaviour of definitely - * freeing the page. - */ - ret = madvise(host_startaddr, length, MADV_DONTNEED); -#endif - } else { - /* Huge page case - unfortunately it can't do DONTNEED, but - * it can do the equivalent by FALLOC_FL_PUNCH_HOLE in the - * huge page file. + /* The logic here is messy; + * madvise DONTNEED fails for hugepages + * fallocate works on hugepages and shmem + */ + need_madvise = (rb->page_size == qemu_host_page_size); + need_fallocate = rb->fd != -1; + if (need_fallocate) { + /* For a file, this causes the area of the file to be zero'd + * if read, and for hugetlbfs also causes it to be unmapped + * so a userfault will trigger. */ #ifdef CONFIG_FALLOCATE_PUNCH_HOLE ret = fallocate(rb->fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, start, length); + if (ret) { + ret = -errno; + error_report("ram_block_discard_range: Failed to fallocate " + "%s:%" PRIx64 " +%zx (%d)", + rb->idstr, start, length, ret); + goto err; + } +#else + ret = -ENOSYS; + error_report("ram_block_discard_range: fallocate not available/file" + "%s:%" PRIx64 " +%zx (%d)", + rb->idstr, start, length, ret); + goto err; #endif } - if (ret) { - ret = -errno; - error_report("ram_block_discard_range: Failed to discard range " + if (need_madvise) { + /* For normal RAM this causes it to be unmapped, + * for shared memory it causes the local mapping to disappear + * and to fall back on the file contents (which we just + * fallocate'd away). + */ +#if defined(CONFIG_MADVISE) + ret = madvise(host_startaddr, length, MADV_DONTNEED); + if (ret) { + ret = -errno; + error_report("ram_block_discard_range: Failed to discard range " + "%s:%" PRIx64 " +%zx (%d)", + rb->idstr, start, length, ret); + goto err; + } +#else + ret = -ENOSYS; + error_report("ram_block_discard_range: MADVISE not available" "%s:%" PRIx64 " +%zx (%d)", rb->idstr, start, length, ret); + goto err; +#endif } + trace_ram_block_discard_range(rb->idstr, host_startaddr, length, + need_madvise, need_fallocate, ret); } else { error_report("ram_block_discard_range: Overrun block '%s' (%" PRIu64 "/%zx/" RAM_ADDR_FMT")", |