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memory: add readonly support to memory_region_init_ram_from_file()

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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.

Signed-off-by: Stefan Hajnoczi <stefanha@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>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20210104171320.575838-2-stefanha@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2021-01-04 17:13:18 +00:00 • committed by Eduardo Habkost
parent 74208cd252
commit 369d6dc4de
8 changed files with 31 additions and 17 deletions
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7
softmmu/memory.c
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@ -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));