* [PATCH v3 1/3] memory: add readonly support to memory_region_init_ram_from_file()
2021-01-04 17:13 [PATCH v3 0/3] nvdimm: read-only file support Stefan Hajnoczi
@ 2021-01-04 17:13 ` Stefan Hajnoczi
2021-01-04 17:13 ` [PATCH v3 2/3] hostmem-file: add readonly=on|off option Stefan Hajnoczi
` (2 subsequent siblings)
3 siblings, 0 replies; 7+ messages in thread
From: Stefan Hajnoczi @ 2021-01-04 17:13 UTC (permalink / raw)
To: qemu-devel
Cc: Xiao Guangrong, Michael S. Tsirkin, Julio Montes, Eduardo Habkost,
eric.g.ernst, Stefan Hajnoczi, Igor Mammedov, Paolo Bonzini,
Philippe Mathieu-Daudé, Richard Henderson
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>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
include/exec/memory.h | 2 ++
include/exec/ram_addr.h | 5 +++--
include/qemu/mmap-alloc.h | 2 ++
backends/hostmem-file.c | 2 +-
softmmu/memory.c | 7 +++++--
softmmu/physmem.c | 18 +++++++++++-------
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 521d9901d7..c6ce74fb79 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -966,6 +966,7 @@ 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
@@ -978,6 +979,7 @@ 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 c6d2ef1d07..40b16609ab 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 40e1e5b3e3..e827692124 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -56,7 +56,7 @@ 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/softmmu/memory.c b/softmmu/memory.c
index 333e1ed7b0..676c298b60 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -1587,15 +1587,18 @@ 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);
if (err) {
mr->size = int128_zero();
object_unparent(OBJECT(mr));
@@ -1618,7 +1621,7 @@ 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);
if (err) {
mr->size = int128_zero();
object_unparent(OBJECT(mr));
diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 2cd1de4a2c..5753cfc39f 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -1398,6 +1398,7 @@ 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)
{
@@ -1408,7 +1409,7 @@ 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;
@@ -1460,6 +1461,7 @@ 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)
{
@@ -1510,7 +1512,7 @@ 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,
@@ -1942,7 +1944,7 @@ 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;
@@ -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, readonly,
+ !file_size, errp);
if (!new_block->host) {
g_free(new_block);
return NULL;
@@ -2015,18 +2018,19 @@ 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/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 f15234b5c0..cfe86553da 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;
--
2.29.2
^ permalink raw reply related [flat|nested] 7+ messages in thread* [PATCH v3 2/3] hostmem-file: add readonly=on|off option
2021-01-04 17:13 [PATCH v3 0/3] nvdimm: read-only file support Stefan Hajnoczi
2021-01-04 17:13 ` [PATCH v3 1/3] memory: add readonly support to memory_region_init_ram_from_file() Stefan Hajnoczi
@ 2021-01-04 17:13 ` Stefan Hajnoczi
2021-01-04 17:13 ` [PATCH v3 3/3] nvdimm: check -object memory-backend-file, readonly=on option Stefan Hajnoczi
2021-01-04 21:02 ` [PATCH v3 0/3] nvdimm: read-only file support Eduardo Habkost
3 siblings, 0 replies; 7+ messages in thread
From: Stefan Hajnoczi @ 2021-01-04 17:13 UTC (permalink / raw)
To: qemu-devel
Cc: Xiao Guangrong, Michael S. Tsirkin, Julio Montes, Eduardo Habkost,
eric.g.ernst, Stefan Hajnoczi, Igor Mammedov, Paolo Bonzini,
Philippe Mathieu-Daudé, Richard Henderson
Let -object memory-backend-file work on read-only files when the
readonly=on option is given. This can be used to share the contents of a
file between multiple guests while preventing them from consuming
Copy-on-Write memory if guests dirty the pages, for example.
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
v3:
* Use Object *obj instead of Object *o [Igor]
* Do not dereference MEMORY_BACKEND_FILE(o)->readonly directly, use a
local variable to hold the HostMemoryBackendFile pointer. [Igor]
---
backends/hostmem-file.c | 28 +++++++++++++++++++++++++++-
qemu-options.hx | 5 ++++-
2 files changed, 31 insertions(+), 2 deletions(-)
diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index e827692124..733408e076 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -29,6 +29,7 @@ struct HostMemoryBackendFile {
uint64_t align;
bool discard_data;
bool is_pmem;
+ bool readonly;
};
static void
@@ -56,7 +57,7 @@ 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, false, errp);
+ fb->mem_path, fb->readonly, errp);
g_free(name);
#endif
}
@@ -151,6 +152,28 @@ static void file_memory_backend_set_pmem(Object *o, bool value, Error **errp)
fb->is_pmem = value;
}
+static bool file_memory_backend_get_readonly(Object *obj, Error **errp)
+{
+ HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(obj);
+
+ return fb->readonly;
+}
+
+static void file_memory_backend_set_readonly(Object *obj, bool value,
+ Error **errp)
+{
+ HostMemoryBackend *backend = MEMORY_BACKEND(obj);
+ HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(obj);
+
+ if (host_memory_backend_mr_inited(backend)) {
+ error_setg(errp, "cannot change property 'readonly' of %s.",
+ object_get_typename(obj));
+ return;
+ }
+
+ fb->readonly = value;
+}
+
static void file_backend_unparent(Object *obj)
{
HostMemoryBackend *backend = MEMORY_BACKEND(obj);
@@ -182,6 +205,9 @@ file_backend_class_init(ObjectClass *oc, void *data)
NULL, NULL);
object_class_property_add_bool(oc, "pmem",
file_memory_backend_get_pmem, file_memory_backend_set_pmem);
+ object_class_property_add_bool(oc, "readonly",
+ file_memory_backend_get_readonly,
+ file_memory_backend_set_readonly);
}
static void file_backend_instance_finalize(Object *o)
diff --git a/qemu-options.hx b/qemu-options.hx
index 459c916d3d..4732c6b45e 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -4407,7 +4407,7 @@ SRST
they are specified. Note that the 'id' property must be set. These
objects are placed in the '/objects' path.
- ``-object memory-backend-file,id=id,size=size,mem-path=dir,share=on|off,discard-data=on|off,merge=on|off,dump=on|off,prealloc=on|off,host-nodes=host-nodes,policy=default|preferred|bind|interleave,align=align``
+ ``-object memory-backend-file,id=id,size=size,mem-path=dir,share=on|off,discard-data=on|off,merge=on|off,dump=on|off,prealloc=on|off,host-nodes=host-nodes,policy=default|preferred|bind|interleave,align=align,readonly=on|off``
Creates a memory file backend object, which can be used to back
the guest RAM with huge pages.
@@ -4490,6 +4490,9 @@ SRST
4.15) and the filesystem of ``mem-path`` mounted with DAX
option.
+ The ``readonly`` option specifies whether the backing file is opened
+ read-only or read-write (default).
+
``-object memory-backend-ram,id=id,merge=on|off,dump=on|off,share=on|off,prealloc=on|off,size=size,host-nodes=host-nodes,policy=default|preferred|bind|interleave``
Creates a memory backend object, which can be used to back the
guest RAM. Memory backend objects offer more control than the
--
2.29.2
^ permalink raw reply related [flat|nested] 7+ messages in thread* [PATCH v3 3/3] nvdimm: check -object memory-backend-file, readonly=on option
2021-01-04 17:13 [PATCH v3 0/3] nvdimm: read-only file support Stefan Hajnoczi
2021-01-04 17:13 ` [PATCH v3 1/3] memory: add readonly support to memory_region_init_ram_from_file() Stefan Hajnoczi
2021-01-04 17:13 ` [PATCH v3 2/3] hostmem-file: add readonly=on|off option Stefan Hajnoczi
@ 2021-01-04 17:13 ` Stefan Hajnoczi
2021-01-04 21:02 ` [PATCH v3 0/3] nvdimm: read-only file support Eduardo Habkost
3 siblings, 0 replies; 7+ messages in thread
From: Stefan Hajnoczi @ 2021-01-04 17:13 UTC (permalink / raw)
To: qemu-devel
Cc: Xiao Guangrong, Michael S. Tsirkin, Julio Montes, Eduardo Habkost,
eric.g.ernst, Stefan Hajnoczi, Igor Mammedov, Paolo Bonzini,
Philippe Mathieu-Daudé, Richard Henderson
Check that -device nvdimm,unarmed=on is used when -object
memory-backend-file,readonly=on and document that -device
nvdimm,unarmed=on|off controls whether the NVDIMM appears read-only to
the guest.
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
v3:
* Produce an error when -device nvdimm,unarmed=off is used with -object
memory-backend-file,readonly=on instead of silently switching on
unarmed. [Igor]
---
docs/nvdimm.txt | 24 +++++++++++++++++-------
hw/mem/nvdimm.c | 9 +++++++++
2 files changed, 26 insertions(+), 7 deletions(-)
diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt
index c2c6e441b3..0aae682be3 100644
--- a/docs/nvdimm.txt
+++ b/docs/nvdimm.txt
@@ -17,8 +17,8 @@ following command line options:
-machine pc,nvdimm
-m $RAM_SIZE,slots=$N,maxmem=$MAX_SIZE
- -object memory-backend-file,id=mem1,share=on,mem-path=$PATH,size=$NVDIMM_SIZE
- -device nvdimm,id=nvdimm1,memdev=mem1
+ -object memory-backend-file,id=mem1,share=on,mem-path=$PATH,size=$NVDIMM_SIZE,readonly=off
+ -device nvdimm,id=nvdimm1,memdev=mem1,unarmed=off
Where,
@@ -31,9 +31,10 @@ Where,
of normal RAM devices and vNVDIMM devices, e.g. $MAX_SIZE should be
>= $RAM_SIZE + $NVDIMM_SIZE here.
- - "object memory-backend-file,id=mem1,share=on,mem-path=$PATH,size=$NVDIMM_SIZE"
- creates a backend storage of size $NVDIMM_SIZE on a file $PATH. All
- accesses to the virtual NVDIMM device go to the file $PATH.
+ - "object memory-backend-file,id=mem1,share=on,mem-path=$PATH,
+ size=$NVDIMM_SIZE,readonly=off" creates a backend storage of size
+ $NVDIMM_SIZE on a file $PATH. All accesses to the virtual NVDIMM device go
+ to the file $PATH.
"share=on/off" controls the visibility of guest writes. If
"share=on", then guest writes will be applied to the backend
@@ -42,8 +43,17 @@ Where,
"share=off", then guest writes won't be applied to the backend
file and thus will be invisible to other guests.
- - "device nvdimm,id=nvdimm1,memdev=mem1" creates a virtual NVDIMM
- device whose storage is provided by above memory backend device.
+ "readonly=on/off" controls whether the file $PATH is opened read-only or
+ read/write (default).
+
+ - "device nvdimm,id=nvdimm1,memdev=mem1,unarmed=off" creates a read/write
+ virtual NVDIMM device whose storage is provided by above memory backend
+ device.
+
+ "unarmed" controls the ACPI NFIT NVDIMM Region Mapping Structure "NVDIMM
+ State Flags" Bit 3 indicating that the device is "unarmed" and cannot accept
+ persistent writes. Linux guest drivers set the device to read-only when this
+ bit is present. Set unarmed to on when the memdev has readonly=on.
Multiple vNVDIMM devices can be created if multiple pairs of "-object"
and "-device" are provided.
diff --git a/hw/mem/nvdimm.c b/hw/mem/nvdimm.c
index 03c2201b56..e0a9d606e1 100644
--- a/hw/mem/nvdimm.c
+++ b/hw/mem/nvdimm.c
@@ -146,6 +146,15 @@ static void nvdimm_prepare_memory_region(NVDIMMDevice *nvdimm, Error **errp)
return;
}
+ if (!nvdimm->unarmed && memory_region_is_rom(mr)) {
+ HostMemoryBackend *hostmem = dimm->hostmem;
+
+ error_setg(errp, "'unarmed' property must be off since memdev %s "
+ "is read-only",
+ object_get_canonical_path_component(OBJECT(hostmem)));
+ return;
+ }
+
nvdimm->nvdimm_mr = g_new(MemoryRegion, 1);
memory_region_init_alias(nvdimm->nvdimm_mr, OBJECT(dimm),
"nvdimm-memory", mr, 0, pmem_size);
--
2.29.2
^ permalink raw reply related [flat|nested] 7+ messages in thread