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* Correct occurrences ofRob Landley2011-05-061-1/+1
| | | | | | | | | | - Documentation/kvm/ to Documentation/virtual/kvm - Documentation/uml/ to Documentation/virtual/uml - Documentation/lguest/ to Documentation/virtual/lguest throughout the kernel source tree. Signed-off-by: Rob Landley <rob@landley.net> Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
* vhost: copy_from_user -> __copy_from_userMichael S. Tsirkin2011-03-081-1/+1
| | | | | | | | copy_from_user is pretty high on perf top profile, replacing it with __copy_from_user helps. It's also safe because we do access_ok checks during setup. Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vhost: Cleanup vhost.c and net.cKrishna Kumar2011-03-081-16/+37
| | | | | | | Minor cleanup of vhost.c and net.c to match coding style. Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vhost: fix signed/unsigned comparisonMichael S. Tsirkin2011-01-101-7/+11
| | | | | | | | | | | To detect that a sequence number is done, we are doing math on unsigned integers so the result is unsigned too. Not what was intended for the <= comparison. The result is user stuck forever in flush call. Convert to int to fix this. Further, get rid of ({}) to make code clearer. Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vhost: better variable name in loggingMichael S. Tsirkin2010-12-091-4/+4
| | | | | | | | We really store a page offset in write_address, so rename it write_page to avoid confusion. Signed-off-by: Jason Wang <jasowang@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vhost: correctly set bits of dirty pagesMichael S. Tsirkin2010-12-091-1/+2
| | | | | | | | | | Fix two bugs in dirty page logging: When counting pages we should increase address by 1 instead of VHOST_PAGE_SIZE. Make log_write() correctly process requests that cross pages with write_address not starting at page boundary. Reported-by: Jason Wang <jasowang@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vhost: remove unused includeMichael S. Tsirkin2010-12-091-2/+0
| | | | | | | vhost.c does not need to know about sockets, don't include sock.h Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vhost: get/put_user -> __get/__put_userMichael S. Tsirkin2010-11-041-8/+8
| | | | | | | We do access_ok checks on all ring values on an ioctl, so we don't need to redo them on each access. Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vhost: copy_to_user -> __copy_to_userMichael S. Tsirkin2010-11-041-1/+1
| | | | | | | We do access_ok checks at setup time, so we don't need to redo them on each access. Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vhost-net: batch use/unuse mmMichael S. Tsirkin2010-11-041-1/+6
| | | | | | | Move use/unuse mm to vhost.c which makes it possible to batch these operations. Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vhost: put mm after thread stopMichael S. Tsirkin2010-11-041-4/+3
| | | | | | makes it possible to batch use/unuse mm Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* drivers/vhost/vhost.c: delete double assignmentJulia Lawall2010-10-261-1/+0
| | | | | | | | | | | | | | | | | | | Delete successive assignments to the same location. A simplified version of the semantic match that finds this problem is as follows: (http://coccinelle.lip6.fr/) // <smpl> @@ expression i; @@ *i = ...; i = ...; // </smpl> Signed-off-by: Julia Lawall <julia@diku.dk> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next-2.6Linus Torvalds2010-10-231-2/+49
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next-2.6: (1699 commits) bnx2/bnx2x: Unsupported Ethtool operations should return -EINVAL. vlan: Calling vlan_hwaccel_do_receive() is always valid. tproxy: use the interface primary IP address as a default value for --on-ip tproxy: added IPv6 support to the socket match cxgb3: function namespace cleanup tproxy: added IPv6 support to the TPROXY target tproxy: added IPv6 socket lookup function to nf_tproxy_core be2net: Changes to use only priority codes allowed by f/w tproxy: allow non-local binds of IPv6 sockets if IP_TRANSPARENT is enabled tproxy: added tproxy sockopt interface in the IPV6 layer tproxy: added udp6_lib_lookup function tproxy: added const specifiers to udp lookup functions tproxy: split off ipv6 defragmentation to a separate module l2tp: small cleanup nf_nat: restrict ICMP translation for embedded header can: mcp251x: fix generation of error frames can: mcp251x: fix endless loop in interrupt handler if CANINTF_MERRF is set can-raw: add msg_flags to distinguish local traffic 9p: client code cleanup rds: make local functions/variables static ... Fix up conflicts in net/core/dev.c, drivers/net/pcmcia/smc91c92_cs.c and drivers/net/wireless/ath/ath9k/debug.c as per David
| * Merge branch 'master' of ↵David S. Miller2010-10-211-1/+1
| |\ | | | | | | | | | | | | | | | | | | master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 Conflicts: net/core/dev.c
| | * vhost: fix return code for log_access_ok()Dan Carpenter2010-10-121-1/+1
| | | | | | | | | | | | | | | | | | | | | access_ok() returns 1 if it's OK otherwise it should return 0. Signed-off-by: Dan Carpenter <error27@gmail.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
| * | vhost: max s/g to match qemuJason Wang2010-10-051-1/+48
| |/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | Qemu supports up to UIO_MAXIOV s/g so we have to match that because guest drivers may rely on this. Allocate indirect and log arrays dynamically to avoid using too much contigious memory and make the length of hdr array to match the header length since each iovec entry has a least one byte. Test with copying large files w/ and w/o migration in both linux and windows guests. Signed-off-by: Jason Wang <jasowang@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* | Merge commit 'v2.6.36-rc7' into core/rcuIngo Molnar2010-10-071-25/+62
|\ \ | |/ | | | | | | | | Merge reason: Update from -rc3 to -rc7. Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * vhost: fix log ctx signallingMichael S. Tsirkin2010-09-221-3/+4
| | | | | | | | | | | | | | | | The log eventfd signalling got put in dead code. We didn't notice because qemu currently does polling instead of eventfd select. Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
| * vhost: error handling fixMichael S. Tsirkin2010-09-061-0/+1
| | | | | | | | | | | | | | vhost should set worker to NULL on cgroups attach failure, so that we won't try to destroy the worker again on close. Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
| * vhost: fix attach to cgroups regressionMichael S. Tsirkin2010-09-061-22/+57
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Since 2.6.36-rc1, non-root users of vhost-net fail to attach if they are in any cgroups. The reason is that when qemu uses vhost, vhost wants to attach its thread to all cgroups that qemu has. But we got the API backwards, so a non-priveledged process (Qemu) tried to control the priveledged one (vhost), which fails. Fix this by switching to the new cgroup_attach_task_all, and running it from the vhost thread. Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* | Merge branch 'rcu/urgent' of ↵Ingo Molnar2010-10-071-1/+4
|\ \ | |/ | | | | git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu into core/rcu
| * vhost: stop worker only if createdEric Dumazet2010-09-011-1/+4
| | | | | | | | | | | | | | | | | | Its currently illegal to call kthread_stop(NULL) Reported-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* | vhost: add __rcu annotationsArnd Bergmann2010-08-211-6/+16
|/ | | | | | | | Also add rcu_dereference_protected() for code paths where locks are held. Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: "Michael S. Tsirkin" <mst@redhat.com>
* vhost-net: mergeable buffers supportDavid Stevens2010-07-281-4/+75
| | | | | | | | | | | | | This adds support for mergeable buffers in vhost-net: this is needed for older guests without indirect buffer support, as well as for zero copy with some devices. Includes changes by Michael S. Tsirkin to make the patch as low risk as possible (i.e., close to no changes when feature is disabled). Signed-off-by: David Stevens <dlstevens@us.ibm.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vhost: apply cgroup to vhost workersMichael S. Tsirkin2010-07-281-0/+6
| | | | | | | | | | | | | | | Apply the cgroup of the owner task to the created vhost worker. Based on patches from Sridhar Samudrala's and Tejun Heo. Later we'll need to also apply cpumask and probably priority of the owner process. Discussion on the best way to do this is still ongoing. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Cc: Tejun Heo <tj@kernel.org> Cc: Sridhar Samudrala <samudrala.sridhar@gmail.com> Cc: Li Zefan <lizf@cn.fujitsu.com>
* vhost: replace vhost_workqueue with per-vhost kthreadTejun Heo2010-07-281-28/+115
| | | | | | | | | | | | | | | | | | | | | | | | | Replace vhost_workqueue with per-vhost kthread. Other than callback argument change from struct work_struct * to struct vhost_work *, there's no visible change to vhost_poll_*() interface. This conversion is to make each vhost use a dedicated kthread so that resource control via cgroup can be applied. Partially based on Sridhar Samudrala's patch. * Updated to use sub structure vhost_work instead of directly using vhost_poll at Michael's suggestion. * Added flusher wake_up() optimization at Michael's suggestion. Changes by MST: * Converted atomics/barrier use to a spinlock. * Create thread on SET_OWNER * Fix flushing Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Cc: Sridhar Samudrala <samudrala.sridhar@gmail.com>
* Merge branch 'master' of ↵David S. Miller2010-07-071-42/+44
|\ | | | | | | master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6
| * vhost: add unlikely annotations to error pathMichael S. Tsirkin2010-07-011-26/+27
| | | | | | | | | | | | | | | | | | patch 'break out of polling loop on error' caused a minor performance regression on my machine: recover that performance by adding a bunch of unlikely annotations in the error handling. Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
| * vhost: break out of polling loop on errorMichael S. Tsirkin2010-06-271-16/+17
| | | | | | | | | | | | | | | | | | | | | | When ring parsing fails, we currently handle this as ring empty condition. This means that we enable kicks and recheck ring empty: if this not empty, we re-start polling which of course will fail again. Instead, let's return a negative error code and stop polling. Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* | Merge branch 'vhost-net-next' of ↵David S. Miller2010-06-021-2/+2
|\ \ | |/ |/| | | git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost
| * vhost: whitespace fixMichael S. Tsirkin2010-05-271-2/+2
| | | | | | | | | | | | | | Fix up whitespace in vq_memory_access_ok. Reported-by: Aristeu Rozanski <aris@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* | Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6Linus Torvalds2010-05-281-25/+32
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6: (22 commits) netlink: bug fix: wrong size was calculated for vfinfo list blob netlink: bug fix: don't overrun skbs on vf_port dump xt_tee: use skb_dst_drop() netdev/fec: fix ifconfig eth0 down hang issue cnic: Fix context memory init. on 5709. drivers/net: Eliminate a NULL pointer dereference drivers/net/hamradio: Eliminate a NULL pointer dereference be2net: Patch removes redundant while statement in loop. ipv6: Add GSO support on forwarding path net: fix __neigh_event_send() vhost: fix the memory leak which will happen when memory_access_ok fails vhost-net: fix to check the return value of copy_to/from_user() correctly vhost: fix to check the return value of copy_to/from_user() correctly vhost: Fix host panic if ioctl called with wrong index net: fix lock_sock_bh/unlock_sock_bh net/iucv: Add missing spin_unlock net: ll_temac: fix checksum offload logic net: ll_temac: fix interrupt bug when interrupt 0 is used sctp: dubious bitfields in sctp_transport ipmr: off by one in __ipmr_fill_mroute() ...
| * | vhost: fix the memory leak which will happen when memory_access_ok failsTakuya Yoshikawa2010-05-271-1/+3
| | | | | | | | | | | | | | | | | | | | | We need to free newmem when vhost_set_memory() fails to complete. Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
| * | vhost: fix to check the return value of copy_to/from_user() correctlyTakuya Yoshikawa2010-05-271-23/+28
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | copy_to/from_user() returns the number of bytes that could not be copied. So we need to check if it is not zero, and in that case, we should return the error number -EFAULT rather than directly return the return value from copy_to/from_user(). Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
| * | vhost: Fix host panic if ioctl called with wrong indexKrishna Kumar2010-05-271-1/+1
| |/ | | | | | | | | | | | | | | Missed a boundary value check in vhost_set_vring. The host panics if idx == nvqs is used in ioctl commands in vhost_virtqueue_init. Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* | kernel-wide: replace USHORT_MAX, SHORT_MAX and SHORT_MIN with USHRT_MAX, ↵Alexey Dobriyan2010-05-251-1/+1
|/ | | | | | | | | | | | | | | | SHRT_MAX and SHRT_MIN - C99 knows about USHRT_MAX/SHRT_MAX/SHRT_MIN, not USHORT_MAX/SHORT_MAX/SHORT_MIN. - Make SHRT_MIN of type s16, not int, for consistency. [akpm@linux-foundation.org: fix drivers/dma/timb_dma.c] [akpm@linux-foundation.org: fix security/keys/keyring.c] Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Acked-by: WANG Cong <xiyou.wangcong@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Merge branch 'master' of ↵David S. Miller2010-05-161-1/+6
|\ | | | | | | | | | | | | master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 Conflicts: include/linux/if_link.h
| * vhost: fix barrier pairingMichael S. Tsirkin2010-05-121-1/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | According to memory-barriers.txt, an smp memory barrier in guest should always be paired with an smp memory barrier in host, and I quote "a lack of appropriate pairing is almost certainly an error". In case of vhost, failure to flush out used index update before looking at the interrupt disable flag could result in missed interrupts, resulting in networking hang under stress. This might happen when flags read bypasses used index write. So we see interrupts disabled and do not interrupt, at the same time guest writes flags value to enable interrupt, reads an old used index value, thinks that used ring is empty and waits for interrupt. Note: the barrier we pair with here is in drivers/virtio/virtio_ring.c, function vring_enable_cb. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Acked-by: Juan Quintela <quintela@redhat.com>
* | Merge branch 'vhost' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhostDavid S. Miller2010-04-141-5/+6
|\ \ | |/ |/|
| * vhost: fix sparse warningsChristoph Hellwig2010-04-141-5/+6
| | | | | | | | | | Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* | Merge branch 'master' of /home/davem/src/GIT/linux-2.6/David S. Miller2010-04-111-0/+1
|\ \ | |/ |/|
| * include cleanup: Update gfp.h and slab.h includes to prepare for breaking ↵Tejun Heo2010-03-301-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | implicit slab.h inclusion from percpu.h percpu.h is included by sched.h and module.h and thus ends up being included when building most .c files. percpu.h includes slab.h which in turn includes gfp.h making everything defined by the two files universally available and complicating inclusion dependencies. percpu.h -> slab.h dependency is about to be removed. Prepare for this change by updating users of gfp and slab facilities include those headers directly instead of assuming availability. As this conversion needs to touch large number of source files, the following script is used as the basis of conversion. http://userweb.kernel.org/~tj/misc/slabh-sweep.py The script does the followings. * Scan files for gfp and slab usages and update includes such that only the necessary includes are there. ie. if only gfp is used, gfp.h, if slab is used, slab.h. * When the script inserts a new include, it looks at the include blocks and try to put the new include such that its order conforms to its surrounding. It's put in the include block which contains core kernel includes, in the same order that the rest are ordered - alphabetical, Christmas tree, rev-Xmas-tree or at the end if there doesn't seem to be any matching order. * If the script can't find a place to put a new include (mostly because the file doesn't have fitting include block), it prints out an error message indicating which .h file needs to be added to the file. The conversion was done in the following steps. 1. The initial automatic conversion of all .c files updated slightly over 4000 files, deleting around 700 includes and adding ~480 gfp.h and ~3000 slab.h inclusions. The script emitted errors for ~400 files. 2. Each error was manually checked. Some didn't need the inclusion, some needed manual addition while adding it to implementation .h or embedding .c file was more appropriate for others. This step added inclusions to around 150 files. 3. The script was run again and the output was compared to the edits from #2 to make sure no file was left behind. 4. Several build tests were done and a couple of problems were fixed. e.g. lib/decompress_*.c used malloc/free() wrappers around slab APIs requiring slab.h to be added manually. 5. The script was run on all .h files but without automatically editing them as sprinkling gfp.h and slab.h inclusions around .h files could easily lead to inclusion dependency hell. Most gfp.h inclusion directives were ignored as stuff from gfp.h was usually wildly available and often used in preprocessor macros. Each slab.h inclusion directive was examined and added manually as necessary. 6. percpu.h was updated not to include slab.h. 7. Build test were done on the following configurations and failures were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my distributed build env didn't work with gcov compiles) and a few more options had to be turned off depending on archs to make things build (like ipr on powerpc/64 which failed due to missing writeq). * x86 and x86_64 UP and SMP allmodconfig and a custom test config. * powerpc and powerpc64 SMP allmodconfig * sparc and sparc64 SMP allmodconfig * ia64 SMP allmodconfig * s390 SMP allmodconfig * alpha SMP allmodconfig * um on x86_64 SMP allmodconfig 8. percpu.h modifications were reverted so that it could be applied as a separate patch and serve as bisection point. Given the fact that I had only a couple of failures from tests on step 6, I'm fairly confident about the coverage of this conversion patch. If there is a breakage, it's likely to be something in one of the arch headers which should be easily discoverable easily on most builds of the specific arch. Signed-off-by: Tejun Heo <tj@kernel.org> Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
* | vhost-net: fix vq_memory_access_ok error checkingJeff Dike2010-04-071-0/+4
|/ | | | | | | vq_memory_access_ok needs to check whether mem == NULL Signed-off-by: Jeff Dike <jdike@linux.intel.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vhost: fix error handling in vring ioctlsMichael S. Tsirkin2010-03-171-6/+12
| | | | | | | | | | | Stanse found a locking problem in vhost_set_vring: several returns from VHOST_SET_VRING_KICK, VHOST_SET_VRING_CALL, VHOST_SET_VRING_ERR with the vq->mutex held. Fix these up. Reported-by: Jiri Slaby <jirislaby@gmail.com> Acked-by: Laurent Chavey <chavey@google.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vhost: fix get_user_pages_fast error handlingMichael S. Tsirkin2010-02-281-1/+2
| | | | | | | | get_user_pages_fast returns number of pages on success, negative value on failure, but never 0. Fix vhost code to match this logic. Reviewed-by: Juan Quintela <quintela@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vhost: initialize log eventfd context pointerMichael S. Tsirkin2010-02-281-0/+1
| | | | | | | | | | vq log eventfd context pointer needs to be initialized, otherwise operation may fail or oops if log is enabled but log eventfd not set by userspace. When log_ctx for device is created, it is copied to the vq. This reset was missing. Reviewed-by: Juan Quintela <quintela@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vhost: logging thinko fixMichael S. Tsirkin2010-02-281-4/+8
| | | | | | | | | | | | vhost was dong some complex math to get offset to log at, and got it wrong by a couple of bytes, while in fact it's simple: get address where we write, subtract start of buffer, add log base. Do it this way. Reviewed-by: Juan Quintela <quintela@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vhost-net: switch to smp barriersMichael S. Tsirkin2010-02-141-5/+5
| | | | | | | | | | | vhost-net only uses memory barriers to control SMP effects (communication with userspace potentially running on a different CPU), so it should use SMP barriers and not mandatory barriers for memory access ordering, as suggested by Documentation/memory-barriers.txt Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Acked-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: David S. Miller <davem@davemloft.net>
* vhost_net: a kernel-level virtio serverMichael S. Tsirkin2010-01-151-0/+1098
What it is: vhost net is a character device that can be used to reduce the number of system calls involved in virtio networking. Existing virtio net code is used in the guest without modification. There's similarity with vringfd, with some differences and reduced scope - uses eventfd for signalling - structures can be moved around in memory at any time (good for migration, bug work-arounds in userspace) - write logging is supported (good for migration) - support memory table and not just an offset (needed for kvm) common virtio related code has been put in a separate file vhost.c and can be made into a separate module if/when more backends appear. I used Rusty's lguest.c as the source for developing this part : this supplied me with witty comments I wouldn't be able to write myself. What it is not: vhost net is not a bus, and not a generic new system call. No assumptions are made on how guest performs hypercalls. Userspace hypervisors are supported as well as kvm. How it works: Basically, we connect virtio frontend (configured by userspace) to a backend. The backend could be a network device, or a tap device. Backend is also configured by userspace, including vlan/mac etc. Status: This works for me, and I haven't see any crashes. Compared to userspace, people reported improved latency (as I save up to 4 system calls per packet), as well as better bandwidth and CPU utilization. Features that I plan to look at in the future: - mergeable buffers - zero copy - scalability tuning: figure out the best threading model to use Note on RCU usage (this is also documented in vhost.h, near private_pointer which is the value protected by this variant of RCU): what is happening is that the rcu_dereference() is being used in a workqueue item. The role of rcu_read_lock() is taken on by the start of execution of the workqueue item, of rcu_read_unlock() by the end of execution of the workqueue item, and of synchronize_rcu() by flush_workqueue()/flush_work(). In the future we might need to apply some gcc attribute or sparse annotation to the function passed to INIT_WORK(). Paul's ack below is for this RCU usage. (Includes fixes by Alan Cox <alan@linux.intel.com>, David L Stevens <dlstevens@us.ibm.com>, Chris Wright <chrisw@redhat.com>) Acked-by: Rusty Russell <rusty@rustcorp.com.au> Acked-by: Arnd Bergmann <arnd@arndb.de> Acked-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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