| Message ID | 20200916095150.755714-2-stefanha@redhat.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | nvdimm: read-only file support | expand |
On Wed, 16 Sep 2020 10:51:48 +0100 Stefan Hajnoczi <stefanha@redhat.com> wrote: > There is currently no way to open(O_RDONLY) and mmap(PROT_READ) when > creating a memory region from a file. This functionality is needed since > the underlying host file may not allow writing. > > Add a bool readonly argument to memory_region_init_ram_from_file() and > the APIs it calls. > > Extend memory_region_init_ram_from_file() rather than introducing a > memory_region_init_rom_from_file() API so that callers can easily make a > choice between read/write and read-only at runtime without calling > different APIs. > > No new RAMBlock flag is introduced for read-only because it's unclear > whether RAMBlocks need to know that they are read-only. Pass a bool > readonly argument instead. > > Both of these design decisions can be changed in the future. It just > seemed like the simplest approach to me. > > Acked-by: Michael S. Tsirkin <mst@redhat.com> > Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Igor Mammedov <imammedo@redhat.com> > --- > include/exec/memory.h | 2 ++ > include/exec/ram_addr.h | 5 +++-- > include/qemu/mmap-alloc.h | 2 ++ > backends/hostmem-file.c | 2 +- > exec.c | 18 +++++++++++------- > softmmu/memory.c | 7 +++++-- > util/mmap-alloc.c | 10 ++++++---- > util/oslib-posix.c | 2 +- > 8 files changed, 31 insertions(+), 17 deletions(-) > > diff --git a/include/exec/memory.h b/include/exec/memory.h > index f1bb2a7df5..a81fa26165 100644 > --- a/include/exec/memory.h > +++ b/include/exec/memory.h > @@ -879,6 +879,7 @@ void memory_region_init_resizeable_ram(MemoryRegion *mr, > * - RAM_PMEM: the memory is persistent memory > * Other bits are ignored now. > * @path: the path in which to allocate the RAM. > + * @readonly: true to open @path for reading, false for read/write. > * @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 > @@ -891,6 +892,7 @@ void memory_region_init_ram_from_file(MemoryRegion *mr, > uint64_t align, > uint32_t ram_flags, > const char *path, > + bool readonly, > Error **errp); > > /** > diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h > index 3ef729a23c..2a0360a0f2 100644 > --- a/include/exec/ram_addr.h > +++ b/include/exec/ram_addr.h > @@ -110,6 +110,7 @@ long qemu_maxrampagesize(void); > * - RAM_PMEM: the backend @mem_path or @fd is persistent memory > * Other bits are ignored. > * @mem_path or @fd: specify the backing file or device > + * @readonly: true to open @path for reading, false for read/write. > * @errp: pointer to Error*, to store an error if it happens > * > * Return: > @@ -118,9 +119,9 @@ long qemu_maxrampagesize(void); > */ > RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr, > uint32_t ram_flags, const char *mem_path, > - Error **errp); > + bool readonly, Error **errp); > RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr, > - uint32_t ram_flags, int fd, > + uint32_t ram_flags, int fd, bool readonly, > Error **errp); > > RAMBlock *qemu_ram_alloc_from_ptr(ram_addr_t size, void *host, > diff --git a/include/qemu/mmap-alloc.h b/include/qemu/mmap-alloc.h > index e786266b92..8b7a5c70f3 100644 > --- a/include/qemu/mmap-alloc.h > +++ b/include/qemu/mmap-alloc.h > @@ -14,6 +14,7 @@ size_t qemu_mempath_getpagesize(const char *mem_path); > * @size: the number of bytes to be mmaped > * @align: if not zero, specify the alignment of the starting mapping address; > * otherwise, the alignment in use will be determined by QEMU. > + * @readonly: true for a read-only mapping, false for read/write. > * @shared: map has RAM_SHARED flag. > * @is_pmem: map has RAM_PMEM flag. > * > @@ -24,6 +25,7 @@ size_t qemu_mempath_getpagesize(const char *mem_path); > void *qemu_ram_mmap(int fd, > size_t size, > size_t align, > + bool readonly, > bool shared, > bool is_pmem); > > diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c > index a3b2e8209e..dffdf142e0 100644 > --- a/backends/hostmem-file.c > +++ b/backends/hostmem-file.c > @@ -58,7 +58,7 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp) > backend->size, fb->align, > (backend->share ? RAM_SHARED : 0) | > (fb->is_pmem ? RAM_PMEM : 0), > - fb->mem_path, errp); > + fb->mem_path, false, errp); > g_free(name); > #endif > } > diff --git a/exec.c b/exec.c > index e34b602bdf..f1e82dad7a 100644 > --- a/exec.c > +++ b/exec.c > @@ -1770,6 +1770,7 @@ static int64_t get_file_align(int fd) > > static int file_ram_open(const char *path, > const char *region_name, > + bool readonly, > bool *created, > Error **errp) > { > @@ -1780,7 +1781,7 @@ static int file_ram_open(const char *path, > > *created = false; > for (;;) { > - fd = open(path, O_RDWR); > + fd = open(path, readonly ? O_RDONLY : O_RDWR); > if (fd >= 0) { > /* @path names an existing file, use it */ > break; > @@ -1832,6 +1833,7 @@ static int file_ram_open(const char *path, > static void *file_ram_alloc(RAMBlock *block, > ram_addr_t memory, > int fd, > + bool readonly, > bool truncate, > Error **errp) > { > @@ -1882,7 +1884,7 @@ static void *file_ram_alloc(RAMBlock *block, > perror("ftruncate"); > } > > - area = qemu_ram_mmap(fd, memory, block->mr->align, > + area = qemu_ram_mmap(fd, memory, block->mr->align, readonly, > block->flags & RAM_SHARED, block->flags & RAM_PMEM); > if (area == MAP_FAILED) { > error_setg_errno(errp, errno, > @@ -2314,7 +2316,7 @@ 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, > + uint32_t ram_flags, int fd, bool readonly, > Error **errp) > { > RAMBlock *new_block; > @@ -2368,7 +2370,8 @@ 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, readonly, > + !file_size, errp); > if (!new_block->host) { > g_free(new_block); > return NULL; > @@ -2387,18 +2390,19 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr, > > RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr, > uint32_t ram_flags, const char *mem_path, > - Error **errp) > + bool readonly, Error **errp) > { > int fd; > bool created; > RAMBlock *block; > > - fd = file_ram_open(mem_path, memory_region_name(mr), &created, errp); > + fd = file_ram_open(mem_path, memory_region_name(mr), readonly, &created, > + errp); > if (fd < 0) { > 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, readonly, errp); > if (!block) { > if (created) { > unlink(mem_path); > diff --git a/softmmu/memory.c b/softmmu/memory.c > index d030eb6f7c..1b0d1d42c6 100644 > --- a/softmmu/memory.c > +++ b/softmmu/memory.c > @@ -1553,15 +1553,18 @@ void memory_region_init_ram_from_file(MemoryRegion *mr, > uint64_t align, > uint32_t ram_flags, > const char *path, > + bool readonly, > Error **errp) > { > Error *err = NULL; > memory_region_init(mr, owner, name, size); > mr->ram = true; > + mr->readonly = readonly; > mr->terminates = true; > mr->destructor = memory_region_destructor_ram; > mr->align = align; > - mr->ram_block = qemu_ram_alloc_from_file(size, mr, ram_flags, path, &err); > + mr->ram_block = qemu_ram_alloc_from_file(size, mr, ram_flags, path, > + readonly, &err); > mr->dirty_log_mask = tcg_enabled() ? (1 << DIRTY_MEMORY_CODE) : 0; > if (err) { > mr->size = int128_zero(); > @@ -1585,7 +1588,7 @@ 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, false, &err); > mr->dirty_log_mask = tcg_enabled() ? (1 << DIRTY_MEMORY_CODE) : 0; > if (err) { > mr->size = int128_zero(); > diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c > index 27dcccd8ec..890fda6a35 100644 > --- a/util/mmap-alloc.c > +++ b/util/mmap-alloc.c > @@ -85,9 +85,11 @@ size_t qemu_mempath_getpagesize(const char *mem_path) > void *qemu_ram_mmap(int fd, > size_t size, > size_t align, > + bool readonly, > bool shared, > bool is_pmem) > { > + int prot; > int flags; > int map_sync_flags = 0; > int guardfd; > @@ -146,8 +148,9 @@ 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); > + prot = PROT_READ | (readonly ? 0 : PROT_WRITE); > + > + ptr = mmap(guardptr + offset, size, prot, flags | map_sync_flags, fd, 0); > > if (ptr == MAP_FAILED && map_sync_flags) { > if (errno == ENOTSUP) { > @@ -171,8 +174,7 @@ void *qemu_ram_mmap(int fd, > * if map failed with MAP_SHARED_VALIDATE | MAP_SYNC, > * we will remove these flags to handle compatibility. > */ > - ptr = mmap(guardptr + offset, size, PROT_READ | PROT_WRITE, > - flags, fd, 0); > + ptr = mmap(guardptr + offset, size, prot, flags, fd, 0); > } > > if (ptr == MAP_FAILED) { > diff --git a/util/oslib-posix.c b/util/oslib-posix.c > index ad8001a4ad..236b3a88c1 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, false, shared, false); > > if (ptr == MAP_FAILED) { > return NULL;
diff --git a/include/exec/memory.h b/include/exec/memory.h index f1bb2a7df5..a81fa26165 100644 --- a/include/exec/memory.h +++ b/include/exec/memory.h @@ -879,6 +879,7 @@ void memory_region_init_resizeable_ram(MemoryRegion *mr, * - RAM_PMEM: the memory is persistent memory * Other bits are ignored now. * @path: the path in which to allocate the RAM. + * @readonly: true to open @path for reading, false for read/write. * @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 @@ -891,6 +892,7 @@ void memory_region_init_ram_from_file(MemoryRegion *mr, uint64_t align, uint32_t ram_flags, const char *path, + bool readonly, Error **errp); /** diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h index 3ef729a23c..2a0360a0f2 100644 --- a/include/exec/ram_addr.h +++ b/include/exec/ram_addr.h @@ -110,6 +110,7 @@ long qemu_maxrampagesize(void); * - RAM_PMEM: the backend @mem_path or @fd is persistent memory * Other bits are ignored. * @mem_path or @fd: specify the backing file or device + * @readonly: true to open @path for reading, false for read/write. * @errp: pointer to Error*, to store an error if it happens * * Return: @@ -118,9 +119,9 @@ long qemu_maxrampagesize(void); */ RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr, uint32_t ram_flags, const char *mem_path, - Error **errp); + bool readonly, Error **errp); RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr, - uint32_t ram_flags, int fd, + uint32_t ram_flags, int fd, bool readonly, Error **errp); RAMBlock *qemu_ram_alloc_from_ptr(ram_addr_t size, void *host, diff --git a/include/qemu/mmap-alloc.h b/include/qemu/mmap-alloc.h index e786266b92..8b7a5c70f3 100644 --- a/include/qemu/mmap-alloc.h +++ b/include/qemu/mmap-alloc.h @@ -14,6 +14,7 @@ size_t qemu_mempath_getpagesize(const char *mem_path); * @size: the number of bytes to be mmaped * @align: if not zero, specify the alignment of the starting mapping address; * otherwise, the alignment in use will be determined by QEMU. + * @readonly: true for a read-only mapping, false for read/write. * @shared: map has RAM_SHARED flag. * @is_pmem: map has RAM_PMEM flag. * @@ -24,6 +25,7 @@ size_t qemu_mempath_getpagesize(const char *mem_path); void *qemu_ram_mmap(int fd, size_t size, size_t align, + bool readonly, bool shared, bool is_pmem); diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c index a3b2e8209e..dffdf142e0 100644 --- a/backends/hostmem-file.c +++ b/backends/hostmem-file.c @@ -58,7 +58,7 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp) backend->size, fb->align, (backend->share ? RAM_SHARED : 0) | (fb->is_pmem ? RAM_PMEM : 0), - fb->mem_path, errp); + fb->mem_path, false, errp); g_free(name); #endif } diff --git a/exec.c b/exec.c index e34b602bdf..f1e82dad7a 100644 --- a/exec.c +++ b/exec.c @@ -1770,6 +1770,7 @@ static int64_t get_file_align(int fd) static int file_ram_open(const char *path, const char *region_name, + bool readonly, bool *created, Error **errp) { @@ -1780,7 +1781,7 @@ static int file_ram_open(const char *path, *created = false; for (;;) { - fd = open(path, O_RDWR); + fd = open(path, readonly ? O_RDONLY : O_RDWR); if (fd >= 0) { /* @path names an existing file, use it */ break; @@ -1832,6 +1833,7 @@ static int file_ram_open(const char *path, static void *file_ram_alloc(RAMBlock *block, ram_addr_t memory, int fd, + bool readonly, bool truncate, Error **errp) { @@ -1882,7 +1884,7 @@ static void *file_ram_alloc(RAMBlock *block, perror("ftruncate"); } - area = qemu_ram_mmap(fd, memory, block->mr->align, + area = qemu_ram_mmap(fd, memory, block->mr->align, readonly, block->flags & RAM_SHARED, block->flags & RAM_PMEM); if (area == MAP_FAILED) { error_setg_errno(errp, errno, @@ -2314,7 +2316,7 @@ 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, + uint32_t ram_flags, int fd, bool readonly, Error **errp) { RAMBlock *new_block; @@ -2368,7 +2370,8 @@ 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, readonly, + !file_size, errp); if (!new_block->host) { g_free(new_block); return NULL; @@ -2387,18 +2390,19 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr, RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr, uint32_t ram_flags, const char *mem_path, - Error **errp) + bool readonly, Error **errp) { int fd; bool created; RAMBlock *block; - fd = file_ram_open(mem_path, memory_region_name(mr), &created, errp); + fd = file_ram_open(mem_path, memory_region_name(mr), readonly, &created, + errp); if (fd < 0) { 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, readonly, errp); if (!block) { if (created) { unlink(mem_path); diff --git a/softmmu/memory.c b/softmmu/memory.c index d030eb6f7c..1b0d1d42c6 100644 --- a/softmmu/memory.c +++ b/softmmu/memory.c @@ -1553,15 +1553,18 @@ void memory_region_init_ram_from_file(MemoryRegion *mr, uint64_t align, uint32_t ram_flags, const char *path, + bool readonly, Error **errp) { Error *err = NULL; memory_region_init(mr, owner, name, size); mr->ram = true; + mr->readonly = readonly; mr->terminates = true; mr->destructor = memory_region_destructor_ram; mr->align = align; - mr->ram_block = qemu_ram_alloc_from_file(size, mr, ram_flags, path, &err); + mr->ram_block = qemu_ram_alloc_from_file(size, mr, ram_flags, path, + readonly, &err); mr->dirty_log_mask = tcg_enabled() ? (1 << DIRTY_MEMORY_CODE) : 0; if (err) { mr->size = int128_zero(); @@ -1585,7 +1588,7 @@ 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, false, &err); mr->dirty_log_mask = tcg_enabled() ? (1 << DIRTY_MEMORY_CODE) : 0; if (err) { mr->size = int128_zero(); diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c index 27dcccd8ec..890fda6a35 100644 --- a/util/mmap-alloc.c +++ b/util/mmap-alloc.c @@ -85,9 +85,11 @@ size_t qemu_mempath_getpagesize(const char *mem_path) void *qemu_ram_mmap(int fd, size_t size, size_t align, + bool readonly, bool shared, bool is_pmem) { + int prot; int flags; int map_sync_flags = 0; int guardfd; @@ -146,8 +148,9 @@ 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); + prot = PROT_READ | (readonly ? 0 : PROT_WRITE); + + ptr = mmap(guardptr + offset, size, prot, flags | map_sync_flags, fd, 0); if (ptr == MAP_FAILED && map_sync_flags) { if (errno == ENOTSUP) { @@ -171,8 +174,7 @@ void *qemu_ram_mmap(int fd, * if map failed with MAP_SHARED_VALIDATE | MAP_SYNC, * we will remove these flags to handle compatibility. */ - ptr = mmap(guardptr + offset, size, PROT_READ | PROT_WRITE, - flags, fd, 0); + ptr = mmap(guardptr + offset, size, prot, flags, fd, 0); } if (ptr == MAP_FAILED) { diff --git a/util/oslib-posix.c b/util/oslib-posix.c index ad8001a4ad..236b3a88c1 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, false, shared, false); if (ptr == MAP_FAILED) { return NULL;