diff options
Diffstat (limited to 'exec.c')
| -rw-r--r-- | exec.c | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/exec.c b/exec.c index 3adf2b1861..8ac556a2d4 100644 --- a/exec.c +++ b/exec.c @@ -45,6 +45,7 @@ #include "exec/address-spaces.h" #include "sysemu/xen-mapcache.h" #include "trace-root.h" + #endif #include "exec/cpu-all.h" #include "qemu/rcu_queue.h" @@ -3294,4 +3295,57 @@ int qemu_ram_foreach_block(RAMBlockIterFunc func, void *opaque) rcu_read_unlock(); return ret; } + +/* + * Unmap pages of memory from start to start+length such that + * they a) read as 0, b) Trigger whatever fault mechanism + * the OS provides for postcopy. + * The pages must be unmapped by the end of the function. + * Returns: 0 on success, none-0 on failure + * + */ +int ram_block_discard_range(RAMBlock *rb, uint64_t start, size_t length) +{ + int ret = -1; + + uint8_t *host_startaddr = rb->host + start; + + if ((uintptr_t)host_startaddr & (rb->page_size - 1)) { + error_report("ram_block_discard_range: Unaligned start address: %p", + host_startaddr); + goto err; + } + + if ((start + length) <= rb->used_length) { + 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", + host_endaddr); + goto err; + } + + errno = ENOTSUP; /* If we are missing MADVISE etc */ + +#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 + if (ret) { + ret = -errno; + error_report("ram_block_discard_range: Failed to discard range " + "%s:%" PRIx64 " +%zx (%d)", + rb->idstr, start, length, ret); + } + } else { + error_report("ram_block_discard_range: Overrun block '%s' (%" PRIu64 + "/%zx/" RAM_ADDR_FMT")", + rb->idstr, start, length, rb->used_length); + } + +err: + return ret; +} + #endif |