postcopy: OS support test

Provide a check to see if the OS we're running on has all the bits
needed for postcopy.

Creates postcopy-ram.c which will get most of the other helpers we need.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Dr. David Alan Gilbert 2015-11-05 18:10:55 +00:00 committed by Juan Quintela
parent c31b098f64
commit eb59db53a4
4 changed files with 182 additions and 1 deletions

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@ -0,0 +1,19 @@
/*
* Postcopy migration for RAM
*
* Copyright 2013 Red Hat, Inc. and/or its affiliates
*
* Authors:
* Dave Gilbert <dgilbert@redhat.com>
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*
*/
#ifndef QEMU_POSTCOPY_RAM_H
#define QEMU_POSTCOPY_RAM_H
/* Return true if the host supports everything we need to do postcopy-ram */
bool postcopy_ram_supported_by_host(void);
#endif

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@ -1,7 +1,7 @@
common-obj-y += migration.o tcp.o common-obj-y += migration.o tcp.o
common-obj-y += vmstate.o common-obj-y += vmstate.o
common-obj-y += qemu-file.o qemu-file-buf.o qemu-file-unix.o qemu-file-stdio.o common-obj-y += qemu-file.o qemu-file-buf.o qemu-file-unix.o qemu-file-stdio.o
common-obj-y += xbzrle.o common-obj-y += xbzrle.o postcopy-ram.o
common-obj-$(CONFIG_RDMA) += rdma.o common-obj-$(CONFIG_RDMA) += rdma.o
common-obj-$(CONFIG_POSIX) += exec.o unix.o fd.o common-obj-$(CONFIG_POSIX) += exec.o unix.o fd.o

157
migration/postcopy-ram.c Normal file
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@ -0,0 +1,157 @@
/*
* Postcopy migration for RAM
*
* Copyright 2013-2015 Red Hat, Inc. and/or its affiliates
*
* Authors:
* Dave Gilbert <dgilbert@redhat.com>
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*
*/
/*
* Postcopy is a migration technique where the execution flips from the
* source to the destination before all the data has been copied.
*/
#include <glib.h>
#include <stdio.h>
#include <unistd.h>
#include "qemu-common.h"
#include "migration/migration.h"
#include "migration/postcopy-ram.h"
#include "sysemu/sysemu.h"
#include "qemu/error-report.h"
#include "trace.h"
/* Postcopy needs to detect accesses to pages that haven't yet been copied
* across, and efficiently map new pages in, the techniques for doing this
* are target OS specific.
*/
#if defined(__linux__)
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <asm/types.h> /* for __u64 */
#endif
#if defined(__linux__) && defined(__NR_userfaultfd)
#include <linux/userfaultfd.h>
static bool ufd_version_check(int ufd)
{
struct uffdio_api api_struct;
uint64_t ioctl_mask;
api_struct.api = UFFD_API;
api_struct.features = 0;
if (ioctl(ufd, UFFDIO_API, &api_struct)) {
error_report("postcopy_ram_supported_by_host: UFFDIO_API failed: %s",
strerror(errno));
return false;
}
ioctl_mask = (__u64)1 << _UFFDIO_REGISTER |
(__u64)1 << _UFFDIO_UNREGISTER;
if ((api_struct.ioctls & ioctl_mask) != ioctl_mask) {
error_report("Missing userfault features: %" PRIx64,
(uint64_t)(~api_struct.ioctls & ioctl_mask));
return false;
}
return true;
}
bool postcopy_ram_supported_by_host(void)
{
long pagesize = getpagesize();
int ufd = -1;
bool ret = false; /* Error unless we change it */
void *testarea = NULL;
struct uffdio_register reg_struct;
struct uffdio_range range_struct;
uint64_t feature_mask;
if ((1ul << qemu_target_page_bits()) > pagesize) {
error_report("Target page size bigger than host page size");
goto out;
}
ufd = syscall(__NR_userfaultfd, O_CLOEXEC);
if (ufd == -1) {
error_report("%s: userfaultfd not available: %s", __func__,
strerror(errno));
goto out;
}
/* Version and features check */
if (!ufd_version_check(ufd)) {
goto out;
}
/*
* We need to check that the ops we need are supported on anon memory
* To do that we need to register a chunk and see the flags that
* are returned.
*/
testarea = mmap(NULL, pagesize, PROT_READ | PROT_WRITE, MAP_PRIVATE |
MAP_ANONYMOUS, -1, 0);
if (testarea == MAP_FAILED) {
error_report("%s: Failed to map test area: %s", __func__,
strerror(errno));
goto out;
}
g_assert(((size_t)testarea & (pagesize-1)) == 0);
reg_struct.range.start = (uintptr_t)testarea;
reg_struct.range.len = pagesize;
reg_struct.mode = UFFDIO_REGISTER_MODE_MISSING;
if (ioctl(ufd, UFFDIO_REGISTER, &reg_struct)) {
error_report("%s userfault register: %s", __func__, strerror(errno));
goto out;
}
range_struct.start = (uintptr_t)testarea;
range_struct.len = pagesize;
if (ioctl(ufd, UFFDIO_UNREGISTER, &range_struct)) {
error_report("%s userfault unregister: %s", __func__, strerror(errno));
goto out;
}
feature_mask = (__u64)1 << _UFFDIO_WAKE |
(__u64)1 << _UFFDIO_COPY |
(__u64)1 << _UFFDIO_ZEROPAGE;
if ((reg_struct.ioctls & feature_mask) != feature_mask) {
error_report("Missing userfault map features: %" PRIx64,
(uint64_t)(~reg_struct.ioctls & feature_mask));
goto out;
}
/* Success! */
ret = true;
out:
if (testarea) {
munmap(testarea, pagesize);
}
if (ufd != -1) {
close(ufd);
}
return ret;
}
#else
/* No target OS support, stubs just fail */
bool postcopy_ram_supported_by_host(void)
{
error_report("%s: No OS support", __func__);
return false;
}
#endif

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@ -37,6 +37,7 @@
#include "qemu/timer.h" #include "qemu/timer.h"
#include "audio/audio.h" #include "audio/audio.h"
#include "migration/migration.h" #include "migration/migration.h"
#include "migration/postcopy-ram.h"
#include "qapi/qmp/qerror.h" #include "qapi/qmp/qerror.h"
#include "qemu/error-report.h" #include "qemu/error-report.h"
#include "qemu/sockets.h" #include "qemu/sockets.h"
@ -1205,6 +1206,10 @@ static int loadvm_postcopy_handle_advise(MigrationIncomingState *mis)
return -1; return -1;
} }
if (!postcopy_ram_supported_by_host()) {
return -1;
}
remote_hps = qemu_get_be64(mis->from_src_file); remote_hps = qemu_get_be64(mis->from_src_file);
if (remote_hps != getpagesize()) { if (remote_hps != getpagesize()) {
/* /*