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![Wei Yang](/assets/img/avatar_default.png)
There are three page size in qemu: real host page size host page size target page size All of them have dedicate variable to represent. For the last two, we use the same form in the whole qemu project, while for the first one we use two forms: qemu_real_host_page_size and getpagesize(). qemu_real_host_page_size is defined to be a replacement of getpagesize(), so let it serve the role. [Note] Not fully tested for some arch or device. Signed-off-by: Wei Yang <richardw.yang@linux.intel.com> Message-Id: <20191013021145.16011-3-richardw.yang@linux.intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
213 lines
5.5 KiB
C
213 lines
5.5 KiB
C
/*
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* Support for RAM backed by mmaped host memory.
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*
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* Copyright (c) 2015 Red Hat, Inc.
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*
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* Authors:
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* Michael S. Tsirkin <mst@redhat.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or
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* later. See the COPYING file in the top-level directory.
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*/
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#ifdef CONFIG_LINUX
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#include <linux/mman.h>
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#else /* !CONFIG_LINUX */
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#define MAP_SYNC 0x0
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#define MAP_SHARED_VALIDATE 0x0
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#endif /* CONFIG_LINUX */
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#include "qemu/osdep.h"
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#include "qemu/mmap-alloc.h"
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#include "qemu/host-utils.h"
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#define HUGETLBFS_MAGIC 0x958458f6
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#ifdef CONFIG_LINUX
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#include <sys/vfs.h>
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#endif
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size_t qemu_fd_getpagesize(int fd)
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{
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#ifdef CONFIG_LINUX
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struct statfs fs;
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int ret;
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if (fd != -1) {
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do {
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ret = fstatfs(fd, &fs);
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} while (ret != 0 && errno == EINTR);
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if (ret == 0 && fs.f_type == HUGETLBFS_MAGIC) {
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return fs.f_bsize;
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}
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}
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#ifdef __sparc__
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/* SPARC Linux needs greater alignment than the pagesize */
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return QEMU_VMALLOC_ALIGN;
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#endif
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#endif
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return qemu_real_host_page_size;
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}
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size_t qemu_mempath_getpagesize(const char *mem_path)
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{
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#ifdef CONFIG_LINUX
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struct statfs fs;
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int ret;
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if (mem_path) {
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do {
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ret = statfs(mem_path, &fs);
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} while (ret != 0 && errno == EINTR);
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if (ret != 0) {
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fprintf(stderr, "Couldn't statfs() memory path: %s\n",
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strerror(errno));
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exit(1);
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}
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if (fs.f_type == HUGETLBFS_MAGIC) {
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/* It's hugepage, return the huge page size */
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return fs.f_bsize;
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}
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}
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#ifdef __sparc__
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/* SPARC Linux needs greater alignment than the pagesize */
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return QEMU_VMALLOC_ALIGN;
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#endif
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#endif
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return qemu_real_host_page_size;
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}
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void *qemu_ram_mmap(int fd,
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size_t size,
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size_t align,
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bool shared,
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bool is_pmem)
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{
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int flags;
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int map_sync_flags = 0;
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int guardfd;
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size_t offset;
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size_t pagesize;
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size_t total;
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void *guardptr;
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void *ptr;
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/*
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* Note: this always allocates at least one extra page of virtual address
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* space, even if size is already aligned.
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*/
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total = size + align;
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#if defined(__powerpc64__) && defined(__linux__)
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/* On ppc64 mappings in the same segment (aka slice) must share the same
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* page size. Since we will be re-allocating part of this segment
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* from the supplied fd, we should make sure to use the same page size, to
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* this end we mmap the supplied fd. In this case, set MAP_NORESERVE to
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* avoid allocating backing store memory.
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* We do this unless we are using the system page size, in which case
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* anonymous memory is OK.
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*/
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flags = MAP_PRIVATE;
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pagesize = qemu_fd_getpagesize(fd);
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if (fd == -1 || pagesize == qemu_real_host_page_size) {
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guardfd = -1;
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flags |= MAP_ANONYMOUS;
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} else {
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guardfd = fd;
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flags |= MAP_NORESERVE;
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}
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#else
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guardfd = -1;
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pagesize = qemu_real_host_page_size;
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flags = MAP_PRIVATE | MAP_ANONYMOUS;
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#endif
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guardptr = mmap(0, total, PROT_NONE, flags, guardfd, 0);
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if (guardptr == MAP_FAILED) {
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return MAP_FAILED;
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}
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assert(is_power_of_2(align));
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/* Always align to host page size */
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assert(align >= pagesize);
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flags = MAP_FIXED;
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flags |= fd == -1 ? MAP_ANONYMOUS : 0;
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flags |= shared ? MAP_SHARED : MAP_PRIVATE;
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if (shared && is_pmem) {
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map_sync_flags = MAP_SYNC | MAP_SHARED_VALIDATE;
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}
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offset = QEMU_ALIGN_UP((uintptr_t)guardptr, align) - (uintptr_t)guardptr;
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ptr = mmap(guardptr + offset, size, PROT_READ | PROT_WRITE,
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flags | map_sync_flags, fd, 0);
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if (ptr == MAP_FAILED && map_sync_flags) {
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if (errno == ENOTSUP) {
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char *proc_link, *file_name;
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int len;
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proc_link = g_strdup_printf("/proc/self/fd/%d", fd);
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file_name = g_malloc0(PATH_MAX);
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len = readlink(proc_link, file_name, PATH_MAX - 1);
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if (len < 0) {
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len = 0;
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}
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file_name[len] = '\0';
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fprintf(stderr, "Warning: requesting persistence across crashes "
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"for backend file %s failed. Proceeding without "
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"persistence, data might become corrupted in case of host "
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"crash.\n", file_name);
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g_free(proc_link);
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g_free(file_name);
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}
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/*
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* if map failed with MAP_SHARED_VALIDATE | MAP_SYNC,
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* we will remove these flags to handle compatibility.
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*/
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ptr = mmap(guardptr + offset, size, PROT_READ | PROT_WRITE,
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flags, fd, 0);
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}
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if (ptr == MAP_FAILED) {
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munmap(guardptr, total);
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return MAP_FAILED;
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}
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if (offset > 0) {
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munmap(guardptr, offset);
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}
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/*
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* Leave a single PROT_NONE page allocated after the RAM block, to serve as
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* a guard page guarding against potential buffer overflows.
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*/
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total -= offset;
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if (total > size + pagesize) {
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munmap(ptr + size + pagesize, total - size - pagesize);
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}
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return ptr;
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}
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void qemu_ram_munmap(int fd, void *ptr, size_t size)
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{
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size_t pagesize;
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if (ptr) {
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/* Unmap both the RAM block and the guard page */
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#if defined(__powerpc64__) && defined(__linux__)
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pagesize = qemu_fd_getpagesize(fd);
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#else
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pagesize = qemu_real_host_page_size;
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#endif
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munmap(ptr, size + pagesize);
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}
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}
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