[PATCH] Support adding a file to qemu's ram allocation

Cam Macdonell
2010-03-05T23:52:53Z

This avoids the need of using qemu_ram_alloc and mmap with MAP_FIXED to map a host file into guest RAM. This function mmaps the opened file anywhere and adds the memory to the ram blocks.

Usage is

qemu_add_file_to_ram(fd, size, MAP_SHARED);
---
cpu-common.h | 1 +
exec.c | 33 +++++++++++++++++++++++++++++++++
2 files changed, 34 insertions(+), 0 deletions(-)

diff --git a/cpu-common.h b/cpu-common.h
index 326513d..2d95079 100644
--- a/cpu-common.h
+++ b/cpu-common.h
@@ -30,6 +30,7 @@ static inline void cpu_register_physical_memory(target_phys_addr_t start_addr,
}

ram_addr_t cpu_get_physical_page_desc(target_phys_addr_t addr);
+ram_addr_t qemu_add_file_to_ram(int, ram_addr_t, int);
ram_addr_t qemu_ram_alloc(ram_addr_t);
void qemu_ram_free(ram_addr_t addr);
/* This should only be used for ram local to a device. */
diff --git a/exec.c b/exec.c
index 69003c2..955adee 100644
--- a/exec.c
+++ b/exec.c
@@ -2623,6 +2623,39 @@ static void *file_ram_alloc(ram_addr_t memory, const char *path)

extern const char *mem_path;

+ram_addr_t qemu_add_file_to_ram(int fd, ram_addr_t size, int flags)
+{
+ RAMBlock *new_block;
+
+ size = TARGET_PAGE_ALIGN(size);
+ new_block = qemu_malloc(sizeof(*new_block));
+
+ // map the file passed as a parameter to be this part of memory
+ new_block->host = mmap(0, size, PROT_READ|PROT_WRITE, flags, fd, 0);
+
+#ifdef MADV_MERGEABLE
+ madvise(new_block->host, size, MADV_MERGEABLE);
+#endif
+
+ new_block->offset = last_ram_offset;
+ new_block->length = size;
+
+ new_block->next = ram_blocks;
+ ram_blocks = new_block;
+
+ phys_ram_dirty = qemu_realloc(phys_ram_dirty,
+ (last_ram_offset + size) >> TARGET_PAGE_BITS);
+ memset(phys_ram_dirty + (last_ram_offset >> TARGET_PAGE_BITS),
+ 0xff, size >> TARGET_PAGE_BITS);
+
+ last_ram_offset += size;
+
+ if (kvm_enabled())
+ kvm_setup_guest_memory(new_block->host, size);
+
+ return new_block->offset;
+}
+
ram_addr_t qemu_ram_alloc(ram_addr_t size)
{
RAMBlock *new_block;
--
1.6.0.6