Re: [PATCHv2 2/2] vhost_net: a kernel-level virtio server
On Tue, Aug 11, 2009 at 08:06:02PM -0400, Gregory Haskins wrote: Michael S. Tsirkin wrote: 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) - 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 tun-like device. In this version I only support raw socket as a backend, which can be bound to e.g. SR IOV, or to macvlan device. Backend is also configured by userspace, including vlan/mac etc. Status: This works for me, and I haven't see any crashes. I have not run any benchmarks yet, compared to userspace, I expect to see improved latency (as I save up to 4 system calls per packet) but not bandwidth/CPU (as TSO and interrupt mitigation are not supported). Features that I plan to look at in the future: - TSO - interrupt mitigation - zero copy Only a quick review for now. Will look closer later. (see inline) Signed-off-by: Michael S. Tsirkin m...@redhat.com v2 --- MAINTAINERS| 10 + arch/x86/kvm/Kconfig |1 + drivers/Makefile |1 + drivers/vhost/Kconfig | 11 + drivers/vhost/Makefile |2 + drivers/vhost/net.c| 411 +++ drivers/vhost/vhost.c | 663 drivers/vhost/vhost.h | 108 +++ include/linux/Kbuild |1 + include/linux/miscdevice.h |1 + include/linux/vhost.h | 100 +++ 11 files changed, 1309 insertions(+), 0 deletions(-) create mode 100644 drivers/vhost/Kconfig create mode 100644 drivers/vhost/Makefile create mode 100644 drivers/vhost/net.c create mode 100644 drivers/vhost/vhost.c create mode 100644 drivers/vhost/vhost.h create mode 100644 include/linux/vhost.h diff --git a/MAINTAINERS b/MAINTAINERS index ebc2691..eb0c1da 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -6312,6 +6312,16 @@ S: Maintained F: Documentation/filesystems/vfat.txt F: fs/fat/ +VIRTIO HOST (VHOST) +P: Michael S. Tsirkin +M: m...@redhat.com +L: k...@vger.kernel.org +L: virtualizat...@lists.osdl.org +L: net...@vger.kernel.org +S: Maintained +F: drivers/vhost/ +F: include/linux/vhost.h + VIA RHINE NETWORK DRIVER P: Roger Luethi M: r...@hellgate.ch diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig index b84e571..94f44d9 100644 --- a/arch/x86/kvm/Kconfig +++ b/arch/x86/kvm/Kconfig @@ -64,6 +64,7 @@ config KVM_AMD # OK, it's a little counter-intuitive to do this, but it puts it neatly under # the virtualization menu. +source drivers/vhost/Kconfig source drivers/lguest/Kconfig source drivers/virtio/Kconfig diff --git a/drivers/Makefile b/drivers/Makefile index bc4205d..1551ae1 100644 --- a/drivers/Makefile +++ b/drivers/Makefile @@ -105,6 +105,7 @@ obj-$(CONFIG_HID) += hid/ obj-$(CONFIG_PPC_PS3) += ps3/ obj-$(CONFIG_OF) += of/ obj-$(CONFIG_SSB) += ssb/ +obj-$(CONFIG_VHOST_NET)+= vhost/ obj-$(CONFIG_VIRTIO) += virtio/ obj-$(CONFIG_VLYNQ)+= vlynq/ obj-$(CONFIG_STAGING) += staging/ diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig new file mode 100644 index 000..d955406 --- /dev/null +++ b/drivers/vhost/Kconfig @@ -0,0 +1,11 @@ +config VHOST_NET + tristate Host kernel accelerator for virtio net + depends on NET EVENTFD + ---help--- + This kernel module can be loaded in host kernel to accelerate + guest networking with virtio_net. Not to be confused with virtio_net + module itself which needs to be loaded in guest kernel. + + To compile this driver as a module, choose M here: the module will + be called vhost_net. + diff --git a/drivers/vhost/Makefile b/drivers/vhost/Makefile new file mode 100644 index 000..72dd020 --- /dev/null +++ b/drivers/vhost/Makefile @@ -0,0 +1,2 @@ +obj-$(CONFIG_VHOST_NET) += vhost_net.o
Re: [PATCHv2 2/2] vhost_net: a kernel-level virtio server
On Tue, Aug 11, 2009 at 08:06:02PM -0400, Gregory Haskins wrote: diff --git a/include/linux/miscdevice.h b/include/linux/miscdevice.h index 0521177..781a8bb 100644 --- a/include/linux/miscdevice.h +++ b/include/linux/miscdevice.h @@ -30,6 +30,7 @@ #define HPET_MINOR 228 #define FUSE_MINOR 229 #define KVM_MINOR 232 +#define VHOST_NET_MINOR233 Would recommend using DYNAMIC-MINOR. Good idea. Thanks! -- MST ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/virtualization
Re: [PATCHv2 2/2] vhost_net: a kernel-level virtio server
Michael S. Tsirkin wrote: On Tue, Aug 11, 2009 at 08:06:02PM -0400, Gregory Haskins wrote: Michael S. Tsirkin wrote: 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) - 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 tun-like device. In this version I only support raw socket as a backend, which can be bound to e.g. SR IOV, or to macvlan device. Backend is also configured by userspace, including vlan/mac etc. Status: This works for me, and I haven't see any crashes. I have not run any benchmarks yet, compared to userspace, I expect to see improved latency (as I save up to 4 system calls per packet) but not bandwidth/CPU (as TSO and interrupt mitigation are not supported). Features that I plan to look at in the future: - TSO - interrupt mitigation - zero copy Only a quick review for now. Will look closer later. (see inline) Signed-off-by: Michael S. Tsirkin m...@redhat.com v2 --- MAINTAINERS| 10 + arch/x86/kvm/Kconfig |1 + drivers/Makefile |1 + drivers/vhost/Kconfig | 11 + drivers/vhost/Makefile |2 + drivers/vhost/net.c| 411 +++ drivers/vhost/vhost.c | 663 drivers/vhost/vhost.h | 108 +++ include/linux/Kbuild |1 + include/linux/miscdevice.h |1 + include/linux/vhost.h | 100 +++ 11 files changed, 1309 insertions(+), 0 deletions(-) create mode 100644 drivers/vhost/Kconfig create mode 100644 drivers/vhost/Makefile create mode 100644 drivers/vhost/net.c create mode 100644 drivers/vhost/vhost.c create mode 100644 drivers/vhost/vhost.h create mode 100644 include/linux/vhost.h diff --git a/MAINTAINERS b/MAINTAINERS index ebc2691..eb0c1da 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -6312,6 +6312,16 @@ S: Maintained F: Documentation/filesystems/vfat.txt F: fs/fat/ +VIRTIO HOST (VHOST) +P: Michael S. Tsirkin +M: m...@redhat.com +L: k...@vger.kernel.org +L: virtualizat...@lists.osdl.org +L: net...@vger.kernel.org +S: Maintained +F: drivers/vhost/ +F: include/linux/vhost.h + VIA RHINE NETWORK DRIVER P: Roger Luethi M: r...@hellgate.ch diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig index b84e571..94f44d9 100644 --- a/arch/x86/kvm/Kconfig +++ b/arch/x86/kvm/Kconfig @@ -64,6 +64,7 @@ config KVM_AMD # OK, it's a little counter-intuitive to do this, but it puts it neatly under # the virtualization menu. +source drivers/vhost/Kconfig source drivers/lguest/Kconfig source drivers/virtio/Kconfig diff --git a/drivers/Makefile b/drivers/Makefile index bc4205d..1551ae1 100644 --- a/drivers/Makefile +++ b/drivers/Makefile @@ -105,6 +105,7 @@ obj-$(CONFIG_HID) += hid/ obj-$(CONFIG_PPC_PS3) += ps3/ obj-$(CONFIG_OF) += of/ obj-$(CONFIG_SSB) += ssb/ +obj-$(CONFIG_VHOST_NET)+= vhost/ obj-$(CONFIG_VIRTIO) += virtio/ obj-$(CONFIG_VLYNQ)+= vlynq/ obj-$(CONFIG_STAGING) += staging/ diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig new file mode 100644 index 000..d955406 --- /dev/null +++ b/drivers/vhost/Kconfig @@ -0,0 +1,11 @@ +config VHOST_NET + tristate Host kernel accelerator for virtio net + depends on NET EVENTFD + ---help--- + This kernel module can be loaded in host kernel to accelerate + guest networking with virtio_net. Not to be confused with virtio_net + module itself which needs to be loaded in guest kernel. + + To compile this driver as a module, choose M here: the module will + be called vhost_net. + diff --git a/drivers/vhost/Makefile b/drivers/vhost/Makefile new file mode 100644 index 000..72dd020 --- /dev/null +++ b/drivers/vhost/Makefile @@ -0,0 +1,2 @@ +obj-$(CONFIG_VHOST_NET) += vhost_net.o +vhost_net-y := vhost.o net.o diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c new file mode 100644 index
Re: [PATCHv2 2/2] vhost_net: a kernel-level virtio server
On Wed, Aug 12, 2009 at 09:01:35AM -0400, Gregory Haskins wrote: I think I understand what your comment above meant: You don't need to do synchronize_rcu() because you can flush the workqueue instead to ensure that all readers have completed. Yes. But if thats true, to me, the rcu_dereference itself is gratuitous, Here's a thesis on what rcu_dereference does (besides documentation): reader does this A: sock = n-sock B: use *sock Say writer does this: C: newsock = allocate socket D: initialize(newsock) E: n-sock = newsock F: flush On Alpha, reads could be reordered. So, on smp, command A could get data from point F, and command B - from point D (uninitialized, from cache). IOW, you get fresh pointer but stale data. So we need to stick a barrier in there. and that pointer is *not* actually RCU protected (nor does it need to be). Heh, if readers are lockless and writer does init/update/sync, this to me spells rcu. -- MST ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/virtualization
Re: [PATCHv2 2/2] vhost_net: a kernel-level virtio server
Michael S. Tsirkin wrote: On Wed, Aug 12, 2009 at 09:01:35AM -0400, Gregory Haskins wrote: I think I understand what your comment above meant: You don't need to do synchronize_rcu() because you can flush the workqueue instead to ensure that all readers have completed. Yes. But if thats true, to me, the rcu_dereference itself is gratuitous, Here's a thesis on what rcu_dereference does (besides documentation): reader does this A: sock = n-sock B: use *sock Say writer does this: C: newsock = allocate socket D: initialize(newsock) E: n-sock = newsock F: flush On Alpha, reads could be reordered. So, on smp, command A could get data from point F, and command B - from point D (uninitialized, from cache). IOW, you get fresh pointer but stale data. So we need to stick a barrier in there. Yes, that is understood. Perhaps you should just use a normal barrier, however. (Or at least a comment that says I am just using this for its barrier). and that pointer is *not* actually RCU protected (nor does it need to be). Heh, if readers are lockless and writer does init/update/sync, this to me spells rcu. More correctly: it smells like RCU, but its not. ;) It's rcu-like, but you are not really using the rcu facilities. I think anyone that knows RCU and reads your code will likely be scratching their heads as well. Its probably not a big deal, as I understand your code now. Just a suggestion to help clarify it. Regards, -Greg signature.asc Description: OpenPGP digital signature ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/virtualization
Re: [PATCHv2 2/2] vhost_net: a kernel-level virtio server
On Wed, Aug 12, 2009 at 09:41:35AM -0400, Gregory Haskins wrote: Michael S. Tsirkin wrote: On Wed, Aug 12, 2009 at 09:01:35AM -0400, Gregory Haskins wrote: I think I understand what your comment above meant: You don't need to do synchronize_rcu() because you can flush the workqueue instead to ensure that all readers have completed. Yes. But if thats true, to me, the rcu_dereference itself is gratuitous, Here's a thesis on what rcu_dereference does (besides documentation): reader does this A: sock = n-sock B: use *sock Say writer does this: C: newsock = allocate socket D: initialize(newsock) E: n-sock = newsock F: flush On Alpha, reads could be reordered. So, on smp, command A could get data from point F, and command B - from point D (uninitialized, from cache). IOW, you get fresh pointer but stale data. So we need to stick a barrier in there. Yes, that is understood. Perhaps you should just use a normal barrier, however. (Or at least a comment that says I am just using this for its barrier). and that pointer is *not* actually RCU protected (nor does it need to be). Heh, if readers are lockless and writer does init/update/sync, this to me spells rcu. More correctly: it smells like RCU, but its not. ;) It's rcu-like, but you are not really using the rcu facilities. I think anyone that knows RCU and reads your code will likely be scratching their heads as well. Its probably not a big deal, as I understand your code now. Just a suggestion to help clarify it. Regards, -Greg OK, I'll add some comments about that. Thanks for the review! -- MST ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/virtualization
Re: [PATCHv2 2/2] vhost_net: a kernel-level virtio server
On Wed, Aug 12, 2009 at 07:11:07AM -0700, Paul E. McKenney wrote: On Wed, Aug 12, 2009 at 04:25:40PM +0300, Michael S. Tsirkin wrote: On Wed, Aug 12, 2009 at 09:01:35AM -0400, Gregory Haskins wrote: I think I understand what your comment above meant: You don't need to do synchronize_rcu() because you can flush the workqueue instead to ensure that all readers have completed. Yes. But if thats true, to me, the rcu_dereference itself is gratuitous, Here's a thesis on what rcu_dereference does (besides documentation): reader does this A: sock = n-sock B: use *sock Say writer does this: C: newsock = allocate socket D: initialize(newsock) E: n-sock = newsock F: flush On Alpha, reads could be reordered. So, on smp, command A could get data from point F, and command B - from point D (uninitialized, from cache). IOW, you get fresh pointer but stale data. So we need to stick a barrier in there. and that pointer is *not* actually RCU protected (nor does it need to be). Heh, if readers are lockless and writer does init/update/sync, this to me spells rcu. If you are using call_rcu(), synchronize_rcu(), or one of the similar primitives, then you absolutely need rcu_read_lock() and rcu_read_unlock(), or one of the similar pairs of primitives. Right. I don't use any of these though. If you -don't- use rcu_read_lock(), then you are pretty much restricted to adding data, but never removing it. Make sense? ;-) Thanx, Paul Since I only access data from a workqueue, I replaced synchronize_rcu with workqueue flush. That's why I don't need rcu_read_lock. -- MST ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/virtualization
Re: [PATCHv2 2/2] vhost_net: a kernel-level virtio server
On Wed, Aug 12, 2009 at 04:25:40PM +0300, Michael S. Tsirkin wrote: On Wed, Aug 12, 2009 at 09:01:35AM -0400, Gregory Haskins wrote: I think I understand what your comment above meant: You don't need to do synchronize_rcu() because you can flush the workqueue instead to ensure that all readers have completed. Yes. But if thats true, to me, the rcu_dereference itself is gratuitous, Here's a thesis on what rcu_dereference does (besides documentation): reader does this A: sock = n-sock B: use *sock Say writer does this: C: newsock = allocate socket D: initialize(newsock) E: n-sock = newsock F: flush On Alpha, reads could be reordered. So, on smp, command A could get data from point F, and command B - from point D (uninitialized, from cache). IOW, you get fresh pointer but stale data. So we need to stick a barrier in there. and that pointer is *not* actually RCU protected (nor does it need to be). Heh, if readers are lockless and writer does init/update/sync, this to me spells rcu. If you are using call_rcu(), synchronize_rcu(), or one of the similar primitives, then you absolutely need rcu_read_lock() and rcu_read_unlock(), or one of the similar pairs of primitives. If you -don't- use rcu_read_lock(), then you are pretty much restricted to adding data, but never removing it. Make sense? ;-) Thanx, Paul ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/virtualization
Re: [PATCHv2 2/2] vhost_net: a kernel-level virtio server
On Wed, Aug 12, 2009 at 05:15:59PM +0300, Michael S. Tsirkin wrote: On Wed, Aug 12, 2009 at 07:11:07AM -0700, Paul E. McKenney wrote: On Wed, Aug 12, 2009 at 04:25:40PM +0300, Michael S. Tsirkin wrote: On Wed, Aug 12, 2009 at 09:01:35AM -0400, Gregory Haskins wrote: I think I understand what your comment above meant: You don't need to do synchronize_rcu() because you can flush the workqueue instead to ensure that all readers have completed. Yes. But if thats true, to me, the rcu_dereference itself is gratuitous, Here's a thesis on what rcu_dereference does (besides documentation): reader does this A: sock = n-sock B: use *sock Say writer does this: C: newsock = allocate socket D: initialize(newsock) E: n-sock = newsock F: flush On Alpha, reads could be reordered. So, on smp, command A could get data from point F, and command B - from point D (uninitialized, from cache). IOW, you get fresh pointer but stale data. So we need to stick a barrier in there. and that pointer is *not* actually RCU protected (nor does it need to be). Heh, if readers are lockless and writer does init/update/sync, this to me spells rcu. If you are using call_rcu(), synchronize_rcu(), or one of the similar primitives, then you absolutely need rcu_read_lock() and rcu_read_unlock(), or one of the similar pairs of primitives. Right. I don't use any of these though. If you -don't- use rcu_read_lock(), then you are pretty much restricted to adding data, but never removing it. Make sense? ;-) Since I only access data from a workqueue, I replaced synchronize_rcu with workqueue flush. That's why I don't need rcu_read_lock. Well, you -do- need -something- that takes on the role of rcu_read_lock(), and in your case you in fact actually do. Your equivalent of rcu_read_lock() is the beginning of execution of a workqueue item, and the equivalent of rcu_read_unlock() is the end of execution of that same workqueue item. Implicit, but no less real. If a couple more uses like this show up, I might need to add this to Documentation/RCU. ;-) Thanx, Paul ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/virtualization
Re: [PATCHv2 2/2] vhost_net: a kernel-level virtio server
On Wed, Aug 12, 2009 at 08:26:39AM -0700, Paul E. McKenney wrote: On Wed, Aug 12, 2009 at 05:15:59PM +0300, Michael S. Tsirkin wrote: On Wed, Aug 12, 2009 at 07:11:07AM -0700, Paul E. McKenney wrote: On Wed, Aug 12, 2009 at 04:25:40PM +0300, Michael S. Tsirkin wrote: On Wed, Aug 12, 2009 at 09:01:35AM -0400, Gregory Haskins wrote: I think I understand what your comment above meant: You don't need to do synchronize_rcu() because you can flush the workqueue instead to ensure that all readers have completed. Yes. But if thats true, to me, the rcu_dereference itself is gratuitous, Here's a thesis on what rcu_dereference does (besides documentation): reader does this A: sock = n-sock B: use *sock Say writer does this: C: newsock = allocate socket D: initialize(newsock) E: n-sock = newsock F: flush On Alpha, reads could be reordered. So, on smp, command A could get data from point F, and command B - from point D (uninitialized, from cache). IOW, you get fresh pointer but stale data. So we need to stick a barrier in there. and that pointer is *not* actually RCU protected (nor does it need to be). Heh, if readers are lockless and writer does init/update/sync, this to me spells rcu. If you are using call_rcu(), synchronize_rcu(), or one of the similar primitives, then you absolutely need rcu_read_lock() and rcu_read_unlock(), or one of the similar pairs of primitives. Right. I don't use any of these though. If you -don't- use rcu_read_lock(), then you are pretty much restricted to adding data, but never removing it. Make sense? ;-) Since I only access data from a workqueue, I replaced synchronize_rcu with workqueue flush. That's why I don't need rcu_read_lock. Well, you -do- need -something- that takes on the role of rcu_read_lock(), and in your case you in fact actually do. Your equivalent of rcu_read_lock() is the beginning of execution of a workqueue item, and the equivalent of rcu_read_unlock() is the end of execution of that same workqueue item. Implicit, but no less real. Well put. I'll add this to comments in my code. If a couple more uses like this show up, I might need to add this to Documentation/RCU. ;-) Thanx, Paul ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/virtualization
Re: [PATCHv2 2/2] vhost_net: a kernel-level virtio server
On Wed, Aug 12, 2009 at 06:51:54PM +0300, Michael S. Tsirkin wrote: On Wed, Aug 12, 2009 at 08:26:39AM -0700, Paul E. McKenney wrote: On Wed, Aug 12, 2009 at 05:15:59PM +0300, Michael S. Tsirkin wrote: On Wed, Aug 12, 2009 at 07:11:07AM -0700, Paul E. McKenney wrote: On Wed, Aug 12, 2009 at 04:25:40PM +0300, Michael S. Tsirkin wrote: On Wed, Aug 12, 2009 at 09:01:35AM -0400, Gregory Haskins wrote: I think I understand what your comment above meant: You don't need to do synchronize_rcu() because you can flush the workqueue instead to ensure that all readers have completed. Yes. But if thats true, to me, the rcu_dereference itself is gratuitous, Here's a thesis on what rcu_dereference does (besides documentation): reader does this A: sock = n-sock B: use *sock Say writer does this: C: newsock = allocate socket D: initialize(newsock) E: n-sock = newsock F: flush On Alpha, reads could be reordered. So, on smp, command A could get data from point F, and command B - from point D (uninitialized, from cache). IOW, you get fresh pointer but stale data. So we need to stick a barrier in there. and that pointer is *not* actually RCU protected (nor does it need to be). Heh, if readers are lockless and writer does init/update/sync, this to me spells rcu. If you are using call_rcu(), synchronize_rcu(), or one of the similar primitives, then you absolutely need rcu_read_lock() and rcu_read_unlock(), or one of the similar pairs of primitives. Right. I don't use any of these though. If you -don't- use rcu_read_lock(), then you are pretty much restricted to adding data, but never removing it. Make sense? ;-) Since I only access data from a workqueue, I replaced synchronize_rcu with workqueue flush. That's why I don't need rcu_read_lock. Well, you -do- need -something- that takes on the role of rcu_read_lock(), and in your case you in fact actually do. Your equivalent of rcu_read_lock() is the beginning of execution of a workqueue item, and the equivalent of rcu_read_unlock() is the end of execution of that same workqueue item. Implicit, but no less real. Well put. I'll add this to comments in my code. Very good, thank you!!! If a couple more uses like this show up, I might need to add this to Documentation/RCU. ;-) And I idly wonder if this approach could replace SRCU. Probably not for protecting the CPU-hotplug notifier chains, but worth some thought. Thanx, Paul ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/virtualization
Re: [PATCHv2 2/2] vhost_net: a kernel-level virtio server
Michael S. Tsirkin wrote: 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) - 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 tun-like device. In this version I only support raw socket as a backend, which can be bound to e.g. SR IOV, or to macvlan device. Backend is also configured by userspace, including vlan/mac etc. Status: This works for me, and I haven't see any crashes. I have not run any benchmarks yet, compared to userspace, I expect to see improved latency (as I save up to 4 system calls per packet) but not bandwidth/CPU (as TSO and interrupt mitigation are not supported). Features that I plan to look at in the future: - TSO - interrupt mitigation - zero copy Only a quick review for now. Will look closer later. (see inline) Signed-off-by: Michael S. Tsirkin m...@redhat.com v2 --- MAINTAINERS| 10 + arch/x86/kvm/Kconfig |1 + drivers/Makefile |1 + drivers/vhost/Kconfig | 11 + drivers/vhost/Makefile |2 + drivers/vhost/net.c| 411 +++ drivers/vhost/vhost.c | 663 drivers/vhost/vhost.h | 108 +++ include/linux/Kbuild |1 + include/linux/miscdevice.h |1 + include/linux/vhost.h | 100 +++ 11 files changed, 1309 insertions(+), 0 deletions(-) create mode 100644 drivers/vhost/Kconfig create mode 100644 drivers/vhost/Makefile create mode 100644 drivers/vhost/net.c create mode 100644 drivers/vhost/vhost.c create mode 100644 drivers/vhost/vhost.h create mode 100644 include/linux/vhost.h diff --git a/MAINTAINERS b/MAINTAINERS index ebc2691..eb0c1da 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -6312,6 +6312,16 @@ S: Maintained F: Documentation/filesystems/vfat.txt F: fs/fat/ +VIRTIO HOST (VHOST) +P: Michael S. Tsirkin +M: m...@redhat.com +L: k...@vger.kernel.org +L: virtualizat...@lists.osdl.org +L: net...@vger.kernel.org +S: Maintained +F: drivers/vhost/ +F: include/linux/vhost.h + VIA RHINE NETWORK DRIVER P: Roger Luethi M: r...@hellgate.ch diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig index b84e571..94f44d9 100644 --- a/arch/x86/kvm/Kconfig +++ b/arch/x86/kvm/Kconfig @@ -64,6 +64,7 @@ config KVM_AMD # OK, it's a little counter-intuitive to do this, but it puts it neatly under # the virtualization menu. +source drivers/vhost/Kconfig source drivers/lguest/Kconfig source drivers/virtio/Kconfig diff --git a/drivers/Makefile b/drivers/Makefile index bc4205d..1551ae1 100644 --- a/drivers/Makefile +++ b/drivers/Makefile @@ -105,6 +105,7 @@ obj-$(CONFIG_HID) += hid/ obj-$(CONFIG_PPC_PS3)+= ps3/ obj-$(CONFIG_OF) += of/ obj-$(CONFIG_SSB)+= ssb/ +obj-$(CONFIG_VHOST_NET) += vhost/ obj-$(CONFIG_VIRTIO) += virtio/ obj-$(CONFIG_VLYNQ) += vlynq/ obj-$(CONFIG_STAGING)+= staging/ diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig new file mode 100644 index 000..d955406 --- /dev/null +++ b/drivers/vhost/Kconfig @@ -0,0 +1,11 @@ +config VHOST_NET + tristate Host kernel accelerator for virtio net + depends on NET EVENTFD + ---help--- + This kernel module can be loaded in host kernel to accelerate + guest networking with virtio_net. Not to be confused with virtio_net + module itself which needs to be loaded in guest kernel. + + To compile this driver as a module, choose M here: the module will + be called vhost_net. + diff --git a/drivers/vhost/Makefile b/drivers/vhost/Makefile new file mode 100644 index 000..72dd020 --- /dev/null +++ b/drivers/vhost/Makefile @@ -0,0 +1,2 @@ +obj-$(CONFIG_VHOST_NET) += vhost_net.o +vhost_net-y := vhost.o net.o diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c new file mode 100644 index 000..a04ffd0 --- /dev/null +++
