On 02/14/2013 05:00 AM, Stefan Berger wrote:
> Add support for file descriptor sets by converting some of the
> command line parameters to use /dev/fdset/%d if -add-fd is found
> to be supported by QEMU. For those devices libvirt now open()s
> the device to obtain the file descriptor and 'transfers' the
> fd using virCommand.
>
> For the following fragments of domain XML
>
>
> <disk type='file' device='disk'>
> <driver name='qemu' type='raw'/>
> <source file='/var/lib/libvirt/images/fc14-x86_64.img'/>
> <target dev='hda' bus='ide'/>
> <address type='drive' controller='0' bus='0' target='0' unit='0'/>
> </disk>
>
> <serial type='dev'>
> <source path='/dev/ttyS0'/>
> <target port='0'/>
> </serial>
> <serial type='pipe'>
> <source path='/tmp/testpipe'/>
> <target port='1'/>
> </serial>
>
> libvirt now creates the following parts for the QEMU command line:
>
> old: -drive file=/var/lib/libvirt/images/fc14-x86_64.img,if=none,id=drive-ide0-0-0,format=raw
> new: -add-fd set=1,fd=23,opaque=RDONLY:/var/lib/libvirt/images/fc14-x86_64.img
> -add-fd set=1,fd=24,opaque=RDWR:/var/lib/libvirt/images/fc14-x86_64.img
> -drive file=/dev/fdset/1,if=none,id=drive-ide0-0-0,format=raw
>
> old: -chardev tty,id=charserial0,path=/dev/ttyS0
> new: -add-fd set=1,fd=30,opaque=/dev/ttyS0
> -chardev tty,id=charserial0,path=/dev/fdset/1
>
> old: -chardev pipe,id=charserial1,path=/tmp/testpipe
> new: -add-fd set=2,fd=32,opaque=/tmp/testpipe
> -chardev pipe,id=charserial1,path=/dev/fdset/2
The example might be a little clearer if you use sets 1, 2, 3 instead of
1, 1, 2.
>
> Test cases are part of this patch now.
>
> Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxxxxxxx>
Hmm, I started reviewing this before I saw that you sent a v7. I'll go
ahead and send anyways, in case it helps.
>
> /**
> + * qemuCommandPrintFDSet:
> + * @fdset: the number of the file descriptor set to which @fd belongs
> + * @fd: fd that will be assigned to QEMU
> + * @open_flags: the flags used for opening the fd; of interest are only
> + * O_RDONLY, O_WRONLY, O_RDWR
> + * @name: optional name of the file
> + *
> + * Write the parameters for the QEMU -add-fd command line option
> + * for the given file descriptor and return the string.
> + * This function for example returns "set=10,fd=20,opaque=RDWR:/foo/bar".
> + */
> +static char *
> +qemuCommandPrintFDSet(int fdset, int fd, int open_flags, const char *name)
> +{
> + const char *mode = "";
> + virBuffer buf = VIR_BUFFER_INITIALIZER;
> +
> + if (name) {
> + switch ((open_flags & O_ACCMODE)) {
> + case O_RDONLY:
> + mode = "RDONLY:";
> + break;
> + case O_WRONLY:
> + mode = "WRONLY:";
> + break;
> + case O_RDWR:
> + mode = "RDWR:";
> + break;
Is it worth a default case when the mode is unrecognized? Then again,
unless the Linux kernel ever gains O_SEARCH/O_EXEC support, there
probably won't ever be any code hitting the default case.
> + }
> + }
> +
> + virBufferAsprintf(&buf, "set=%d,fd=%d%s%s", fdset, fd,
> + (name) ? ",opaque=" : "",
> + mode);
> + if (name)
> + virBufferEscape(&buf, ',', ",", "%s", name);
Slightly easier to read as:
virBufferAsprintf(&buf, "set=%d,fd=%d", fdset, fd);
if (name)
virBufferEscape(&buf, ',', ",", ",opaque=%s", name);
> +static int
> +qemuCreatePathForFilePath(virQEMUDriverPtr driver, virBufferPtr buf,
> + const char *prefix, const char *path,
> + const int *open_flags,
> + virCommandPtr cmd, virFdSetPtr fdset,
> + const virDomainDeviceInfoPtr info,
> + virQEMUCapsPtr qemuCaps)
> +{
> + char *fdsetstr = NULL;
> + int i;
> +
> + virBufferAdd(buf, prefix, -1);
> + /*
> + * cmd == NULL hints at hotplugging; use old way of doing things
> + * fdset == NULL hints at a call path where we should not open files
> + * In this case we fall back to the old command line
> + * (at least for now)
> + */
> + if (!cmd || !fdset || !virQEMUCapsGet(qemuCaps, QEMU_CAPS_ADD_FD)) {
> + virBufferEscape(buf, ',', ",", "%s", path);
> + } else {
> + unsigned int fdsetnum;
> +
> + if (virFdSetNextSet(fdset, info->alias, &fdsetnum) < 0)
> + goto error;
> +
> + qemuCommandPrintDevSet(buf, fdsetnum);
> +
> + i = 0;
> + while (open_flags[i] != -1) {
Laine was mentioning in another review that we aren't very consistent
between open_flags and openFlags for local variable names, but that the
studlyCaps version seems to be more popular.
Rather than having the user supply a sentinel, would it be better to
have the user provide nopenFlags? That is, when opening a single fd,
passing '&mode, 1' is easier than passing 'int[] { mode, -1}',
especially if we don't want to use C99 initializer syntax. For that
matter, would it be any easier to pass a flags instead of a mode, where
we have the bitwise-or of:
QEMU_USE_RDONLY = 1 << 0, // O_RDONLY
QEMU_USE_RDWR = 1 << 1, // O_RDWR
QEMU_USE WRONLY = 1 << 2, // O_WRONLY
on the grounds that writing 'QEMU_USE_RDONLY | QEMU_USE_RDWR' looks a
little cleaner than writing '(int[]){O_RDONLY, O_RDWR, -1}' (no
temporary arrays required).
> Index: libvirt/tests/qemuxml2argvdata/qemuxml2argv-add-fd.args
> ===================================================================
> --- /dev/null
> +++ libvirt/tests/qemuxml2argvdata/qemuxml2argv-add-fd.args
> @@ -0,0 +1,23 @@
> +LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test \
> +/usr/bin/qemu -S -M pc -m 214 -smp 1 -nographic -nodefaults \
> +-chardev socket,id=charmonitor,path=/tmp/test-monitor,server,nowait \
> +-mon chardev=charmonitor,id=monitor,mode=readline -no-acpi -boot c -usb \
> +\
> +-add-fd set=1,fd=3,opaque=RDONLY:/dev/null \
> +-add-fd set=1,fd=4,opaque=RDWR:/dev/null \
> +-drive file=/dev/fdset/1,if=none,id=drive-ide0-0-0 \
> +-device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 \
> +\
Interesting way to make it more legible - I like it.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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