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Add option to use file backed guest memory

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Port qemu-kvm's -mem-path and -mem-prealloc options. These are useful
for backing guest memory with huge pages via hugetlbfs.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
CC: john cooper <john.cooper@redhat.com>
This commit is contained in:
Marcelo Tosatti 2010-03-01 20:25:08 -03:00
parent 60e4c6317b
commit c902760fb2
4 changed files with 142 additions and 6 deletions
Download patch file Download diff file Expand all files Collapse all files

117
exec.c
View file

@ -2529,6 +2529,99 @@ void qemu_flush_coalesced_mmio_buffer(void)
kvm_flush_coalesced_mmio_buffer();
}
#if defined(__linux__) && !defined(TARGET_S390X)
#include <sys/vfs.h>
#define HUGETLBFS_MAGIC 0x958458f6
static long gethugepagesize(const char *path)
{
struct statfs fs;
int ret;
do {
ret = statfs(path, &fs);
} while (ret != 0 && errno == EINTR);
if (ret != 0) {
perror("statfs");
return 0;
}
if (fs.f_type != HUGETLBFS_MAGIC)
fprintf(stderr, "Warning: path not on HugeTLBFS: %s\n", path);
return fs.f_bsize;
}
static void *file_ram_alloc(ram_addr_t memory, const char *path)
{
char *filename;
void *area;
int fd;
#ifdef MAP_POPULATE
int flags;
#endif
unsigned long hpagesize;
hpagesize = gethugepagesize(path);
if (!hpagesize) {
return NULL;
}
if (memory < hpagesize) {
return NULL;
}
if (kvm_enabled() && !kvm_has_sync_mmu()) {
fprintf(stderr, "host lacks kvm mmu notifiers, -mem-path unsupported\n");
return NULL;
}
if (asprintf(&filename, "%s/qemu_back_mem.XXXXXX", path) == -1) {
return NULL;
}
fd = mkstemp(filename);
if (fd < 0) {
perror("mkstemp");
free(filename);
return NULL;
}
unlink(filename);
free(filename);
memory = (memory+hpagesize-1) & ~(hpagesize-1);
/*
* ftruncate is not supported by hugetlbfs in older
* hosts, so don't bother bailing out on errors.
* If anything goes wrong with it under other filesystems,
* mmap will fail.
*/
if (ftruncate(fd, memory))
perror("ftruncate");
#ifdef MAP_POPULATE
/* NB: MAP_POPULATE won't exhaustively alloc all phys pages in the case
* MAP_PRIVATE is requested. For mem_prealloc we mmap as MAP_SHARED
* to sidestep this quirk.
*/
flags = mem_prealloc ? MAP_POPULATE | MAP_SHARED : MAP_PRIVATE;
area = mmap(0, memory, PROT_READ | PROT_WRITE, flags, fd, 0);
#else
area = mmap(0, memory, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
#endif
if (area == MAP_FAILED) {
perror("file_ram_alloc: can't mmap RAM pages");
close(fd);
return (NULL);
}
return area;
}
#endif
ram_addr_t qemu_ram_alloc(ram_addr_t size)
{
RAMBlock *new_block;
@ -2536,16 +2629,28 @@ ram_addr_t qemu_ram_alloc(ram_addr_t size)
size = TARGET_PAGE_ALIGN(size);
new_block = qemu_malloc(sizeof(*new_block));
#if defined(TARGET_S390X) && defined(CONFIG_KVM)
/* XXX S390 KVM requires the topmost vma of the RAM to be < 256GB */
new_block->host = mmap((void*)0x1000000, size, PROT_EXEC|PROT_READ|PROT_WRITE,
MAP_SHARED | MAP_ANONYMOUS, -1, 0);
if (mem_path) {
#if defined (__linux__) && !defined(TARGET_S390X)
new_block->host = file_ram_alloc(size, mem_path);
if (!new_block->host)
exit(1);
#else
new_block->host = qemu_vmalloc(size);
fprintf(stderr, "-mem-path option unsupported\n");
exit(1);
#endif
} else {
#if defined(TARGET_S390X) && defined(CONFIG_KVM)
/* XXX S390 KVM requires the topmost vma of the RAM to be < 256GB */
new_block->host = mmap((void*)0x1000000, size,
PROT_EXEC|PROT_READ|PROT_WRITE,
MAP_SHARED | MAP_ANONYMOUS, -1, 0);
#else
new_block->host = qemu_vmalloc(size);
#endif
#ifdef MADV_MERGEABLE
madvise(new_block->host, size, MADV_MERGEABLE);
madvise(new_block->host, size, MADV_MERGEABLE);
#endif
}
new_block->offset = last_ram_offset;
new_block->length = size;