From 61c490e25e081af39ff40556f6c1229b8b011585 Mon Sep 17 00:00:00 2001 From: Beata Michalska Date: Thu, 21 Nov 2019 00:08:41 +0000 Subject: Memory: Enable writeback for given memory region Add an option to trigger memory writeback to sync given memory region with the corresponding backing store, case one is available. This extends the support for persistent memory, allowing syncing on-demand. Signed-off-by: Beata Michalska Reviewed-by: Richard Henderson Message-id: 20191121000843.24844-3-beata.michalska@linaro.org Signed-off-by: Peter Maydell --- util/cutils.c | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) (limited to 'util') diff --git a/util/cutils.c b/util/cutils.c index 77acadc..2380165 100644 --- a/util/cutils.c +++ b/util/cutils.c @@ -164,6 +164,44 @@ int qemu_fdatasync(int fd) #endif } +/** + * Sync changes made to the memory mapped file back to the backing + * storage. For POSIX compliant systems this will fallback + * to regular msync call. Otherwise it will trigger whole file sync + * (including the metadata case there is no support to skip that otherwise) + * + * @addr - start of the memory area to be synced + * @length - length of the are to be synced + * @fd - file descriptor for the file to be synced + * (mandatory only for POSIX non-compliant systems) + */ +int qemu_msync(void *addr, size_t length, int fd) +{ +#ifdef CONFIG_POSIX + size_t align_mask = ~(qemu_real_host_page_size - 1); + + /** + * There are no strict reqs as per the length of mapping + * to be synced. Still the length needs to follow the address + * alignment changes. Additionally - round the size to the multiple + * of PAGE_SIZE + */ + length += ((uintptr_t)addr & (qemu_real_host_page_size - 1)); + length = (length + ~align_mask) & align_mask; + + addr = (void *)((uintptr_t)addr & align_mask); + + return msync(addr, length, MS_SYNC); +#else /* CONFIG_POSIX */ + /** + * Perform the sync based on the file descriptor + * The sync range will most probably be wider than the one + * requested - but it will still get the job done + */ + return qemu_fdatasync(fd); +#endif /* CONFIG_POSIX */ +} + #ifndef _WIN32 /* Sets a specific flag */ int fcntl_setfl(int fd, int flag) -- cgit v1.1