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Add option to use file backed guest memory
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>
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60e4c6317b
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c902760fb2
@ -847,6 +847,9 @@ extern uint8_t *phys_ram_dirty;
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extern ram_addr_t ram_size;
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extern ram_addr_t last_ram_offset;
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extern const char *mem_path;
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extern int mem_prealloc;
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/* physical memory access */
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/* MMIO pages are identified by a combination of an IO device index and
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117
exec.c
117
exec.c
@ -2529,6 +2529,99 @@ void qemu_flush_coalesced_mmio_buffer(void)
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kvm_flush_coalesced_mmio_buffer();
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}
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#if defined(__linux__) && !defined(TARGET_S390X)
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#include <sys/vfs.h>
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#define HUGETLBFS_MAGIC 0x958458f6
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static long gethugepagesize(const char *path)
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{
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struct statfs fs;
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int ret;
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do {
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ret = statfs(path, &fs);
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} while (ret != 0 && errno == EINTR);
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if (ret != 0) {
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perror("statfs");
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return 0;
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}
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if (fs.f_type != HUGETLBFS_MAGIC)
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fprintf(stderr, "Warning: path not on HugeTLBFS: %s\n", path);
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return fs.f_bsize;
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}
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static void *file_ram_alloc(ram_addr_t memory, const char *path)
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{
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char *filename;
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void *area;
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int fd;
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#ifdef MAP_POPULATE
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int flags;
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#endif
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unsigned long hpagesize;
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hpagesize = gethugepagesize(path);
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if (!hpagesize) {
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return NULL;
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}
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if (memory < hpagesize) {
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return NULL;
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}
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if (kvm_enabled() && !kvm_has_sync_mmu()) {
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fprintf(stderr, "host lacks kvm mmu notifiers, -mem-path unsupported\n");
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return NULL;
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}
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if (asprintf(&filename, "%s/qemu_back_mem.XXXXXX", path) == -1) {
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return NULL;
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}
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fd = mkstemp(filename);
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if (fd < 0) {
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perror("mkstemp");
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free(filename);
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return NULL;
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}
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unlink(filename);
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free(filename);
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memory = (memory+hpagesize-1) & ~(hpagesize-1);
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/*
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* ftruncate is not supported by hugetlbfs in older
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* hosts, so don't bother bailing out on errors.
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* If anything goes wrong with it under other filesystems,
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* mmap will fail.
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*/
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if (ftruncate(fd, memory))
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perror("ftruncate");
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#ifdef MAP_POPULATE
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/* NB: MAP_POPULATE won't exhaustively alloc all phys pages in the case
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* MAP_PRIVATE is requested. For mem_prealloc we mmap as MAP_SHARED
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* to sidestep this quirk.
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*/
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flags = mem_prealloc ? MAP_POPULATE | MAP_SHARED : MAP_PRIVATE;
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area = mmap(0, memory, PROT_READ | PROT_WRITE, flags, fd, 0);
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#else
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area = mmap(0, memory, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
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#endif
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if (area == MAP_FAILED) {
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perror("file_ram_alloc: can't mmap RAM pages");
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close(fd);
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return (NULL);
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}
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return area;
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}
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#endif
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ram_addr_t qemu_ram_alloc(ram_addr_t size)
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{
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RAMBlock *new_block;
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@ -2536,16 +2629,28 @@ ram_addr_t qemu_ram_alloc(ram_addr_t size)
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size = TARGET_PAGE_ALIGN(size);
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new_block = qemu_malloc(sizeof(*new_block));
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#if defined(TARGET_S390X) && defined(CONFIG_KVM)
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/* XXX S390 KVM requires the topmost vma of the RAM to be < 256GB */
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new_block->host = mmap((void*)0x1000000, size, PROT_EXEC|PROT_READ|PROT_WRITE,
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MAP_SHARED | MAP_ANONYMOUS, -1, 0);
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if (mem_path) {
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#if defined (__linux__) && !defined(TARGET_S390X)
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new_block->host = file_ram_alloc(size, mem_path);
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if (!new_block->host)
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exit(1);
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#else
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new_block->host = qemu_vmalloc(size);
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fprintf(stderr, "-mem-path option unsupported\n");
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exit(1);
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#endif
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} else {
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#if defined(TARGET_S390X) && defined(CONFIG_KVM)
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/* XXX S390 KVM requires the topmost vma of the RAM to be < 256GB */
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new_block->host = mmap((void*)0x1000000, size,
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PROT_EXEC|PROT_READ|PROT_WRITE,
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MAP_SHARED | MAP_ANONYMOUS, -1, 0);
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#else
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new_block->host = qemu_vmalloc(size);
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#endif
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#ifdef MADV_MERGEABLE
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madvise(new_block->host, size, MADV_MERGEABLE);
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madvise(new_block->host, size, MADV_MERGEABLE);
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#endif
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}
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new_block->offset = last_ram_offset;
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new_block->length = size;
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@ -314,6 +314,22 @@ a suffix of ``M'' or ``G'' can be used to signify a value in megabytes or
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gigabytes respectively.
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ETEXI
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DEF("mem-path", HAS_ARG, QEMU_OPTION_mempath,
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"-mem-path FILE provide backing storage for guest RAM\n")
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STEXI
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@item -mem-path @var{path}
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Allocate guest RAM from a temporarily created file in @var{path}.
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ETEXI
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#ifdef MAP_POPULATE
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DEF("mem-prealloc", 0, QEMU_OPTION_mem_prealloc,
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"-mem-prealloc preallocate guest memory (use with -mem-path)\n")
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STEXI
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@item -mem-prealloc
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Preallocate memory when using -mem-path.
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ETEXI
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#endif
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DEF("k", HAS_ARG, QEMU_OPTION_k,
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"-k language use keyboard layout (for example 'fr' for French)\n")
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STEXI
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12
vl.c
12
vl.c
@ -185,6 +185,10 @@ enum vga_retrace_method vga_retrace_method = VGA_RETRACE_DUMB;
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DisplayType display_type = DT_DEFAULT;
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const char* keyboard_layout = NULL;
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ram_addr_t ram_size;
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const char *mem_path = NULL;
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#ifdef MAP_POPULATE
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int mem_prealloc = 0; /* force preallocation of physical target memory */
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#endif
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int nb_nics;
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NICInfo nd_table[MAX_NICS];
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int vm_running;
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@ -5216,6 +5220,14 @@ int main(int argc, char **argv, char **envp)
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ram_size = value;
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break;
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}
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case QEMU_OPTION_mempath:
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mem_path = optarg;
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break;
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#ifdef MAP_POPULATE
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case QEMU_OPTION_mem_prealloc:
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mem_prealloc = 1;
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break;
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#endif
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case QEMU_OPTION_d:
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{
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int mask;
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