On Wed, Dec 2, 2020 at 12:23 AM Jagannathan Raman wrote: > Allow RAM MemoryRegion to be created from an offset in a file, instead > of allocating at offset of 0 by default. This is needed to synchronize > RAM between QEMU & remote process. > > Signed-off-by: Jagannathan Raman > Signed-off-by: John G Johnson > Signed-off-by: Elena Ufimtseva > Reviewed-by: Stefan Hajnoczi > --- > include/exec/memory.h | 2 ++ > include/exec/ram_addr.h | 2 +- > include/qemu/mmap-alloc.h | 3 ++- > backends/hostmem-memfd.c | 2 +- > hw/misc/ivshmem.c | 3 ++- > softmmu/memory.c | 3 ++- > softmmu/physmem.c | 11 +++++++---- > util/mmap-alloc.c | 7 ++++--- > util/oslib-posix.c | 2 +- > 9 files changed, 22 insertions(+), 13 deletions(-) > > diff --git a/include/exec/memory.h b/include/exec/memory.h > index 0f3e6bc..7bcaada 100644 > --- a/include/exec/memory.h > +++ b/include/exec/memory.h > @@ -980,6 +980,7 @@ void memory_region_init_ram_from_file(MemoryRegion *mr, > * @size: size of the region. > * @share: %true if memory must be mmaped with the MAP_SHARED flag > * @fd: the fd to mmap. > + * @offset: offset within the file referenced by fd > * @errp: pointer to Error*, to store an error if it happens. > * > * Note that this function does not do anything to cause the data in the > @@ -991,6 +992,7 @@ void memory_region_init_ram_from_fd(MemoryRegion *mr, > uint64_t size, > bool share, > int fd, > + ram_addr_t offset, > Error **errp); > #endif > > diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h > index c6d2ef1..d465a48 100644 > --- a/include/exec/ram_addr.h > +++ b/include/exec/ram_addr.h > @@ -121,7 +121,7 @@ RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, > MemoryRegion *mr, > Error **errp); > RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr, > uint32_t ram_flags, int fd, > - Error **errp); > + off_t offset, Error **errp); > > RAMBlock *qemu_ram_alloc_from_ptr(ram_addr_t size, void *host, > MemoryRegion *mr, Error **errp); > diff --git a/include/qemu/mmap-alloc.h b/include/qemu/mmap-alloc.h > index e786266..4f57985 100644 > --- a/include/qemu/mmap-alloc.h > +++ b/include/qemu/mmap-alloc.h > @@ -25,7 +25,8 @@ void *qemu_ram_mmap(int fd, > size_t size, > size_t align, > bool shared, > - bool is_pmem); > + bool is_pmem, > + off_t start); > I'd suggest to keep the variable name "offset", to avoid potential confusion (it's also the name of the mmap() argument). > void qemu_ram_munmap(int fd, void *ptr, size_t size); > > diff --git a/backends/hostmem-memfd.c b/backends/hostmem-memfd.c > index e5626d4..69b0ae3 100644 > --- a/backends/hostmem-memfd.c > +++ b/backends/hostmem-memfd.c > @@ -55,7 +55,7 @@ memfd_backend_memory_alloc(HostMemoryBackend *backend, > Error **errp) > name = host_memory_backend_get_name(backend); > memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend), > name, backend->size, > - backend->share, fd, errp); > + backend->share, fd, 0, errp); > g_free(name); > } > > diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c > index e321e5c..8d3e1ee 100644 > --- a/hw/misc/ivshmem.c > +++ b/hw/misc/ivshmem.c > @@ -494,7 +494,8 @@ static void process_msg_shmem(IVShmemState *s, int fd, > Error **errp) > > /* mmap the region and map into the BAR2 */ > memory_region_init_ram_from_fd(&s->server_bar2, OBJECT(s), > - "ivshmem.bar2", size, true, fd, > &local_err); > + "ivshmem.bar2", size, true, fd, 0, > + &local_err); > if (local_err) { > error_propagate(errp, local_err); > return; > diff --git a/softmmu/memory.c b/softmmu/memory.c > index 11ca94d..e4ed0e4 100644 > --- a/softmmu/memory.c > +++ b/softmmu/memory.c > @@ -1612,6 +1612,7 @@ void memory_region_init_ram_from_fd(MemoryRegion *mr, > uint64_t size, > bool share, > int fd, > + ram_addr_t offset, > Error **errp) > { > Error *err = NULL; > @@ -1621,7 +1622,7 @@ void memory_region_init_ram_from_fd(MemoryRegion *mr, > mr->destructor = memory_region_destructor_ram; > mr->ram_block = qemu_ram_alloc_from_fd(size, mr, > share ? RAM_SHARED : 0, > - fd, &err); > + fd, offset, &err); > mr->dirty_log_mask = tcg_enabled() ? (1 << DIRTY_MEMORY_CODE) : 0; > if (err) { > mr->size = int128_zero(); > diff --git a/softmmu/physmem.c b/softmmu/physmem.c > index 3027747..e0b8fc6 100644 > --- a/softmmu/physmem.c > +++ b/softmmu/physmem.c > @@ -1461,6 +1461,7 @@ static void *file_ram_alloc(RAMBlock *block, > ram_addr_t memory, > int fd, > bool truncate, > + off_t offset, > Error **errp) > { > void *area; > @@ -1511,7 +1512,8 @@ static void *file_ram_alloc(RAMBlock *block, > } > > area = qemu_ram_mmap(fd, memory, block->mr->align, > - block->flags & RAM_SHARED, block->flags & > RAM_PMEM); > + block->flags & RAM_SHARED, block->flags & > RAM_PMEM, > + offset); > if (area == MAP_FAILED) { > error_setg_errno(errp, errno, > "unable to map backing store for guest RAM"); > @@ -1943,7 +1945,7 @@ static void ram_block_add(RAMBlock *new_block, Error > **errp, bool shared) > #ifdef CONFIG_POSIX > RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr, > uint32_t ram_flags, int fd, > - Error **errp) > + off_t offset, Error **errp) > { > RAMBlock *new_block; > Error *local_err = NULL; > @@ -1996,7 +1998,8 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, > MemoryRegion *mr, > new_block->used_length = size; > new_block->max_length = size; > new_block->flags = ram_flags; > - new_block->host = file_ram_alloc(new_block, size, fd, !file_size, > errp); > + new_block->host = file_ram_alloc(new_block, size, fd, !file_size, > offset, > + errp); > if (!new_block->host) { > g_free(new_block); > return NULL; > @@ -2026,7 +2029,7 @@ RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, > MemoryRegion *mr, > return NULL; > } > > - block = qemu_ram_alloc_from_fd(size, mr, ram_flags, fd, errp); > + block = qemu_ram_alloc_from_fd(size, mr, ram_flags, fd, 0, errp); > if (!block) { > if (created) { > unlink(mem_path); > diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c > index 27dcccd..a28f702 100644 > --- a/util/mmap-alloc.c > +++ b/util/mmap-alloc.c > @@ -86,7 +86,8 @@ void *qemu_ram_mmap(int fd, > size_t size, > size_t align, > bool shared, > - bool is_pmem) > + bool is_pmem, > + off_t start) > { > int flags; > int map_sync_flags = 0; > @@ -147,7 +148,7 @@ void *qemu_ram_mmap(int fd, > offset = QEMU_ALIGN_UP((uintptr_t)guardptr, align) - > (uintptr_t)guardptr; > > ptr = mmap(guardptr + offset, size, PROT_READ | PROT_WRITE, > - flags | map_sync_flags, fd, 0); > + flags | map_sync_flags, fd, start); > > if (ptr == MAP_FAILED && map_sync_flags) { > if (errno == ENOTSUP) { > @@ -172,7 +173,7 @@ void *qemu_ram_mmap(int fd, > * we will remove these flags to handle compatibility. > */ > ptr = mmap(guardptr + offset, size, PROT_READ | PROT_WRITE, > - flags, fd, 0); > + flags, fd, start); > } > > if (ptr == MAP_FAILED) { > diff --git a/util/oslib-posix.c b/util/oslib-posix.c > index f15234b..93874df 100644 > --- a/util/oslib-posix.c > +++ b/util/oslib-posix.c > @@ -227,7 +227,7 @@ void *qemu_memalign(size_t alignment, size_t size) > void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared) > { > size_t align = QEMU_VMALLOC_ALIGN; > - void *ptr = qemu_ram_mmap(-1, size, align, shared, false); > + void *ptr = qemu_ram_mmap(-1, size, align, shared, false, 0); > > if (ptr == MAP_FAILED) { > return NULL; > -- > 1.8.3.1 > > -- Marc-André Lureau