57d1f6d7ce
SPARC Linux has an oddity that it insists that mmap() of MAP_FIXED memory must be at an alignment defined by SHMLBA, which is more aligned than the page size (typically, SHMLBA alignment is to 16K, and pages are 8K). This is a relic of ancient hardware that had cache aliasing constraints, but even on modern hardware the kernel still insists on the alignment. To ensure that we get mmap() alignment sufficient to make the kernel happy, change QEMU_VMALLOC_ALIGN, qemu_fd_getpagesize() and qemu_mempath_getpagesize() to use the maximum of getpagesize() and SHMLBA. In particular, this allows 'make check' to pass on Sparc: we were previously failing the ivshmem tests. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Message-id: 1512752248-17857-1-git-send-email-peter.maydell@linaro.org
143 lines
3.7 KiB
C
143 lines
3.7 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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#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 getpagesize();
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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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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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#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 getpagesize();
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}
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void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared)
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{
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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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size_t 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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int anonfd = fd == -1 || qemu_fd_getpagesize(fd) == getpagesize() ? -1 : fd;
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int flags = anonfd == -1 ? MAP_ANONYMOUS : MAP_NORESERVE;
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void *ptr = mmap(0, total, PROT_NONE, flags | MAP_PRIVATE, anonfd, 0);
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#else
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void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
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#endif
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size_t offset;
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void *ptr1;
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if (ptr == 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 >= getpagesize());
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offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr;
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ptr1 = mmap(ptr + offset, size, PROT_READ | PROT_WRITE,
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MAP_FIXED |
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(fd == -1 ? MAP_ANONYMOUS : 0) |
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(shared ? MAP_SHARED : MAP_PRIVATE),
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fd, 0);
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if (ptr1 == MAP_FAILED) {
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munmap(ptr, total);
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return MAP_FAILED;
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}
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if (offset > 0) {
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munmap(ptr, 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 + getpagesize()) {
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munmap(ptr1 + size + getpagesize(), total - size - getpagesize());
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}
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return ptr1;
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}
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void qemu_ram_munmap(void *ptr, size_t size)
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{
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if (ptr) {
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/* Unmap both the RAM block and the guard page */
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munmap(ptr, size + getpagesize());
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}
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}
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