From d3a5038c461b9436e5bc82a802b7a843b79f417f Mon Sep 17 00:00:00 2001 From: Dr. David Alan Gilbert Date: Fri, 24 Feb 2017 18:28:32 +0000 Subject: exec: ram_block_discard_range Create ram_block_discard_range in exec.c to replace postcopy_ram_discard_range and most of ram_discard_range. Those two routines are a bit of a weird combination, and ram_discard_range is about to get more complex for hugepages. It's OS dependent code (so shouldn't be in migration/ram.c) but it needs quite a bit of the innards of RAMBlock so doesn't belong in the os*.c. Signed-off-by: Dr. David Alan Gilbert Reviewed-by: Juan Quintela Reviewed-by: Laurent Vivier Message-Id: <20170224182844.32452-5-dgilbert@redhat.com> Signed-off-by: Dr. David Alan Gilbert --- exec.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) (limited to 'exec.c') 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 -- cgit v1.2.3-55-g7522