qemu-ga: add initial win32 support

This adds a win32 channel implementation that makes qemu-ga functional
on Windows using virtio-serial (unix-listen/isa-serial not currently
implemented). Unlike with the posix implementation, we do not use
GIOChannel for the following reasons:

 - glib calls stat() on an fd to check whether S_IFCHR is set, which is
   the case for virtio-serial on win32. Because of that, a one-time
   check to determine whether the channel is readable is done by making
   a call to PeekConsoleInput(), which reports the underlying handle is
   not a valid console handle, and thus we can never read from the
   channel.

 - if one goes as far as to "trick" glib into thinking it is a normal
   file descripter, the buffering is done in such a way that data
   written to the output stream will subsequently result in that same
   data being read back as if it were input, causing an error loop.
   furthermore, a forced flush of the channel only moves the data into a
   secondary buffer managed by glib, so there's no way to prevent output
   from getting read back as input.

The implementation here ties into the glib main loop by implementing a
custom GSource that continually submits asynchronous/overlapped I/O to
fill an GAChannel-managed read buffer, and tells glib to poll the
corresponding event handle for a completion whenever there is no
data/RPC in the read buffer to notify the main application about.
This commit is contained in:
Michael Roth 2012-01-20 19:01:30 -06:00
parent d8ca685acb
commit 7868e26e59
3 changed files with 345 additions and 1 deletions

View File

@ -426,7 +426,7 @@ common-obj-y += qmp.o hmp.o
qga-nested-y = commands.o guest-agent-command-state.o
qga-nested-$(CONFIG_POSIX) += commands-posix.o channel-posix.o
qga-nested-$(CONFIG_WIN32) += commands-win32.o
qga-nested-$(CONFIG_WIN32) += commands-win32.o channel-win32.o
qga-obj-y = $(addprefix qga/, $(qga-nested-y))
qga-obj-y += qemu-ga.o module.o
qga-obj-$(CONFIG_WIN32) += oslib-win32.o

View File

@ -30,7 +30,11 @@
#include "qapi/qmp-core.h"
#include "qga/channel.h"
#ifndef _WIN32
#define QGA_VIRTIO_PATH_DEFAULT "/dev/virtio-ports/org.qemu.guest_agent.0"
#else
#define QGA_VIRTIO_PATH_DEFAULT "\\\\.\\Global\\org.qemu.guest_agent.0"
#endif
#define QGA_PIDFILE_DEFAULT "/var/run/qemu-ga.pid"
struct GAState {

340
qga/channel-win32.c Normal file
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@ -0,0 +1,340 @@
#include <stdlib.h>
#include <stdio.h>
#include <stdbool.h>
#include <glib.h>
#include <windows.h>
#include <errno.h>
#include <io.h>
#include "qga/guest-agent-core.h"
#include "qga/channel.h"
typedef struct GAChannelReadState {
guint thread_id;
uint8_t *buf;
size_t buf_size;
size_t cur; /* current buffer start */
size_t pending; /* pending buffered bytes to read */
OVERLAPPED ov;
bool ov_pending; /* whether on async read is outstanding */
} GAChannelReadState;
struct GAChannel {
HANDLE handle;
GAChannelCallback cb;
gpointer user_data;
GAChannelReadState rstate;
GIOCondition pending_events; /* TODO: use GAWatch.pollfd.revents */
GSource *source;
};
typedef struct GAWatch {
GSource source;
GPollFD pollfd;
GAChannel *channel;
GIOCondition events_mask;
} GAWatch;
/*
* Called by glib prior to polling to set up poll events if polling is needed.
*
*/
static gboolean ga_channel_prepare(GSource *source, gint *timeout_ms)
{
GAWatch *watch = (GAWatch *)source;
GAChannel *c = (GAChannel *)watch->channel;
GAChannelReadState *rs = &c->rstate;
DWORD count_read, count_to_read = 0;
bool success;
GIOCondition new_events = 0;
g_debug("prepare");
/* go ahead and submit another read if there's room in the buffer
* and no previous reads are outstanding
*/
if (!rs->ov_pending) {
if (rs->cur + rs->pending >= rs->buf_size) {
if (rs->cur) {
memmove(rs->buf, rs->buf + rs->cur, rs->pending);
rs->cur = 0;
}
}
count_to_read = rs->buf_size - rs->cur - rs->pending;
}
if (rs->ov_pending || count_to_read <= 0) {
goto out;
}
/* submit the read */
success = ReadFile(c->handle, rs->buf + rs->cur + rs->pending,
count_to_read, &count_read, &rs->ov);
if (success) {
rs->pending += count_read;
rs->ov_pending = false;
} else {
if (GetLastError() == ERROR_IO_PENDING) {
rs->ov_pending = true;
} else {
new_events |= G_IO_ERR;
}
}
out:
/* dont block forever, iterate the main loop every once and a while */
*timeout_ms = 500;
/* if there's data in the read buffer, or another event is pending,
* skip polling and issue user cb.
*/
if (rs->pending) {
new_events |= G_IO_IN;
}
c->pending_events |= new_events;
return !!c->pending_events;
}
/*
* Called by glib after an outstanding read request is completed.
*/
static gboolean ga_channel_check(GSource *source)
{
GAWatch *watch = (GAWatch *)source;
GAChannel *c = (GAChannel *)watch->channel;
GAChannelReadState *rs = &c->rstate;
DWORD count_read, error;
BOOL success;
GIOCondition new_events = 0;
g_debug("check");
/* failing this implies we issued a read that completed immediately,
* yet no data was placed into the buffer (and thus we did not skip
* polling). but since EOF is not obtainable until we retrieve an
* overlapped result, it must be the case that there was data placed
* into the buffer, or an error was generated by Readfile(). in either
* case, we should've skipped the polling for this round.
*/
g_assert(rs->ov_pending);
success = GetOverlappedResult(c->handle, &rs->ov, &count_read, FALSE);
if (success) {
g_debug("thread: overlapped result, count_read: %d", (int)count_read);
rs->pending += count_read;
new_events |= G_IO_IN;
} else {
error = GetLastError();
if (error == 0 || error == ERROR_HANDLE_EOF ||
error == ERROR_NO_SYSTEM_RESOURCES ||
error == ERROR_OPERATION_ABORTED) {
/* note: On WinXP SP3 with rhel6ga virtio-win-1.1.16 vioser drivers,
* ENSR seems to be synonymous with when we'd normally expect
* ERROR_HANDLE_EOF. So treat it as such. Microsoft's
* recommendation for ERROR_NO_SYSTEM_RESOURCES is to
* retry the read, so this happens to work out anyway. On newer
* virtio-win driver, this seems to be replaced with EOA, so
* handle that in the same fashion.
*/
new_events |= G_IO_HUP;
} else if (error != ERROR_IO_INCOMPLETE) {
g_critical("error retrieving overlapped result: %d", (int)error);
new_events |= G_IO_ERR;
}
}
if (new_events) {
rs->ov_pending = 0;
}
c->pending_events |= new_events;
return !!c->pending_events;
}
/*
* Called by glib after either prepare or check routines signal readiness
*/
static gboolean ga_channel_dispatch(GSource *source, GSourceFunc unused,
gpointer user_data)
{
GAWatch *watch = (GAWatch *)source;
GAChannel *c = (GAChannel *)watch->channel;
GAChannelReadState *rs = &c->rstate;
gboolean success;
g_debug("dispatch");
success = c->cb(watch->pollfd.revents, c->user_data);
if (c->pending_events & G_IO_ERR) {
g_critical("channel error, removing source");
return false;
}
/* TODO: replace rs->pending with watch->revents */
c->pending_events &= ~G_IO_HUP;
if (!rs->pending) {
c->pending_events &= ~G_IO_IN;
} else {
c->pending_events = 0;
}
return success;
}
static void ga_channel_finalize(GSource *source)
{
g_debug("finalize");
}
GSourceFuncs ga_channel_watch_funcs = {
ga_channel_prepare,
ga_channel_check,
ga_channel_dispatch,
ga_channel_finalize
};
static GSource *ga_channel_create_watch(GAChannel *c)
{
GSource *source = g_source_new(&ga_channel_watch_funcs, sizeof(GAWatch));
GAWatch *watch = (GAWatch *)source;
watch->channel = c;
watch->pollfd.fd = (gintptr) c->rstate.ov.hEvent;
g_source_add_poll(source, &watch->pollfd);
return source;
}
GIOStatus ga_channel_read(GAChannel *c, char *buf, size_t size, gsize *count)
{
GAChannelReadState *rs = &c->rstate;
GIOStatus status;
size_t to_read = 0;
if (c->pending_events & G_IO_ERR) {
return G_IO_STATUS_ERROR;
}
*count = to_read = MIN(size, rs->pending);
if (to_read) {
memcpy(buf, rs->buf + rs->cur, to_read);
rs->cur += to_read;
rs->pending -= to_read;
status = G_IO_STATUS_NORMAL;
} else {
status = G_IO_STATUS_AGAIN;
}
return status;
}
static GIOStatus ga_channel_write(GAChannel *c, const char *buf, size_t size,
size_t *count)
{
GIOStatus status;
OVERLAPPED ov = {0};
BOOL ret;
DWORD written;
ov.hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
ret = WriteFile(c->handle, buf, size, &written, &ov);
if (!ret) {
if (GetLastError() == ERROR_IO_PENDING) {
/* write is pending */
ret = GetOverlappedResult(c->handle, &ov, &written, TRUE);
if (!ret) {
if (!GetLastError()) {
status = G_IO_STATUS_AGAIN;
} else {
status = G_IO_STATUS_ERROR;
}
} else {
/* write is complete */
status = G_IO_STATUS_NORMAL;
*count = written;
}
} else {
status = G_IO_STATUS_ERROR;
}
} else {
/* write returned immediately */
status = G_IO_STATUS_NORMAL;
*count = written;
}
return status;
}
GIOStatus ga_channel_write_all(GAChannel *c, const char *buf, size_t size)
{
GIOStatus status = G_IO_STATUS_NORMAL;;
size_t count;
while (size) {
status = ga_channel_write(c, buf, size, &count);
if (status == G_IO_STATUS_NORMAL) {
size -= count;
buf += count;
} else if (status != G_IO_STATUS_AGAIN) {
break;
}
}
return status;
}
static gboolean ga_channel_open(GAChannel *c, GAChannelMethod method,
const gchar *path)
{
if (!method == GA_CHANNEL_VIRTIO_SERIAL) {
g_critical("unsupported communication method");
return false;
}
c->handle = CreateFile(path, GENERIC_READ | GENERIC_WRITE, 0, NULL,
OPEN_EXISTING,
FILE_FLAG_NO_BUFFERING | FILE_FLAG_OVERLAPPED, NULL);
if (c->handle == INVALID_HANDLE_VALUE) {
g_critical("error opening path");
return false;
}
return true;
}
GAChannel *ga_channel_new(GAChannelMethod method, const gchar *path,
GAChannelCallback cb, gpointer opaque)
{
GAChannel *c = g_malloc0(sizeof(GAChannel));
SECURITY_ATTRIBUTES sec_attrs;
if (!ga_channel_open(c, method, path)) {
g_critical("error opening channel");
g_free(c);
return NULL;
}
c->cb = cb;
c->user_data = opaque;
sec_attrs.nLength = sizeof(SECURITY_ATTRIBUTES);
sec_attrs.lpSecurityDescriptor = NULL;
sec_attrs.bInheritHandle = false;
c->rstate.buf_size = QGA_READ_COUNT_DEFAULT;
c->rstate.buf = g_malloc(QGA_READ_COUNT_DEFAULT);
c->rstate.ov.hEvent = CreateEvent(&sec_attrs, FALSE, FALSE, NULL);
c->source = ga_channel_create_watch(c);
g_source_attach(c->source, NULL);
return c;
}
void ga_channel_free(GAChannel *c)
{
if (c->source) {
g_source_destroy(c->source);
}
if (c->rstate.ov.hEvent) {
CloseHandle(c->rstate.ov.hEvent);
}
g_free(c->rstate.buf);
g_free(c);
}