[libvirt] [PATCH V6 3/3] Add support for file descriptor sets
Corey Bryant
coreyb at linux.vnet.ibm.com
Fri Feb 15 20:51:25 UTC 2013
On 02/14/2013 07:00 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
>
> Test cases are part of this patch now.
>
> Signed-off-by: Stefan Berger<stefanb at linux.vnet.ibm.com>
>
> ---
> v4->v5:
> - removed one test case testing for 'old' command line
>
> v3->v4:
> - Adapt to changes in patch 1
> - better handling of error case on the hotplug code
>
> v2->v3:
> - Use an unsigned int for remembering the next-to-use fdset
>
> v1->v2:
> - Addressed many of Eric's comment; many changes, though
> - virBitmap holds used file descriptor sets; it's attached to
> QEMU private domain structure
> - persisting and parsing the fdset in the virDomainDeviceInfo XML
> - rebuilding the fdset bitmap upon libvirt start and after parsing
> the virDomainDeviceInfo XML
>
> ---
> src/qemu/qemu_command.c | 243 +++++++++++++++++++-----
> src/qemu/qemu_command.h | 14 +
> src/qemu/qemu_driver.c | 5
> src/qemu/qemu_driver.h | 4
> src/qemu/qemu_hotplug.c | 15 +
> src/qemu/qemu_process.c | 4
> tests/qemuxml2argvdata/qemuxml2argv-add-fd.args | 23 ++
> tests/qemuxml2argvdata/qemuxml2argv-add-fd.xml | 36 +++
> tests/qemuxml2argvtest.c | 11 -
> tests/qemuxmlnstest.c | 8
> 10 files changed, 308 insertions(+), 55 deletions(-)
>
> Index: libvirt/src/qemu/qemu_command.c
> ===================================================================
> --- libvirt.orig/src/qemu/qemu_command.c
> +++ libvirt/src/qemu/qemu_command.c
> @@ -46,6 +46,7 @@
> #include "base64.h"
> #include "device_conf.h"
> #include "virstoragefile.h"
> +#include "qemu_driver.h"
>
> #include <sys/stat.h>
> #include <fcntl.h>
> @@ -133,6 +134,70 @@ VIR_ENUM_IMPL(qemuDomainFSDriver, VIR_DO
>
>
> /**
> + * 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)
It would be easier to read the code if this were called something like
qemuCommandPrintAddFd().
> +{
> + 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;
> + }
> + }
> +
> + virBufferAsprintf(&buf, "set=%d,fd=%d%s%s", fdset, fd,
> + (name) ? ",opaque=" : "",
> + mode);
> + if (name)
> + virBufferEscape(&buf, ',', ",", "%s", name);
> +
> + if (virBufferError(&buf)) {
> + virReportOOMError();
> + virBufferFreeAndReset(&buf);
> + return NULL;
> + }
> +
> + return virBufferContentAndReset(&buf);
> +}
> +
> +/**
> + * qemuCommandPrintDevSet:
> + * @buf: buffer to write the file descriptor set string
> + * @fdset: the file descriptor set
> + *
> + * Get the parameters for the QEMU path= parameter where a file
> + * descriptor is accessed via a file descriptor set, for example
> + * /dev/fdset/10. The file descriptor must previously have been
> + * 'transferred' in a virCommandTransfer() call.
> + */
> +static void
> +qemuCommandPrintDevSet(virBufferPtr buf, int fdset)
And this could be called qemuCommandPrintDevFdSet().
> +{
> + virBufferAsprintf(buf, "/dev/fdset/%d", fdset);
> +}
> +
> +
> +/**
> * qemuPhysIfaceConnect:
> * @def: the definition of the VM (needed by 802.1Qbh and audit)
> * @driver: pointer to the driver instance
> @@ -2229,11 +2294,70 @@ no_memory:
> goto cleanup;
> }
>
> +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
I assume hotplug will be implemented at a later time by someone.
> + * 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) {
> + int fd = qemuOpenFile(driver, path, open_flags[i], NULL, NULL);
> + if (fd < 0) {
> + virReportError(VIR_ERR_INTERNAL_ERROR,
> + _("Could not open %s"), path);
> + goto error;
> + }
> + virCommandTransferFD(cmd, fd);
> +
> + fdsetstr = qemuCommandPrintFDSet(fdsetnum, fd, open_flags[i],
> + path);
And fdsetstr could be called addfdstr?
> + if (!fdsetstr)
> + goto error;
> + virCommandAddArgList(cmd, "-add-fd", fdsetstr, NULL);
> + VIR_FREE(fdsetstr);
> +
> + i++;
> + }
> + }
> +
> + return 0;
> +
> +error:
Do fd's need to get cleaned up? Are we leaking them here?
> + virFdSetRemoveAlias(fdset, info->alias);
> + return -1;
> +}
> +
--
Regards,
Corey Bryant
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