path: root/virt/kvm/eventfd.c
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2011-04-07Merge branch 'kvm-updates/2.6.39' of git:// Torvalds
* 'kvm-updates/2.6.39' of git:// KVM: move and fix substitue search for missing CPUID entries KVM: fix XSAVE bit scanning KVM: Enable async page fault processing KVM: fix crash on irqfd deassign
2011-04-06KVM: fix crash on irqfd deassignMichael S. Tsirkin
irqfd in kvm used flush_work incorrectly: it assumed that work scheduled previously can't run after flush_work, but since kvm uses a non-reentrant workqueue (by means of schedule_work) we need flush_work_sync to get that guarantee. Signed-off-by: Michael S. Tsirkin <> Reported-by: Jean-Philippe Menil <> Tested-by: Jean-Philippe Menil <> Signed-off-by: Avi Kivity <>
2011-03-31Fix common misspellingsLucas De Marchi
Fixes generated by 'codespell' and manually reviewed. Signed-off-by: Lucas De Marchi <>
2011-03-17KVM: improve comment on rcu use in irqfd_deassignMichael S. Tsirkin
The RCU use in kvm_irqfd_deassign is tricky: we have rcu_assign_pointer but no synchronize_rcu: synchronize_rcu is done by kvm_irq_routing_update which we share a spinlock with. Fix up a comment in an attempt to make this clearer. Signed-off-by: Michael S. Tsirkin <> Signed-off-by: Avi Kivity <>
2011-01-12KVM: fast-path msi injection with irqfdMichael S. Tsirkin
Store irq routing table pointer in the irqfd object, and use that to inject MSI directly without bouncing out to a kernel thread. While we touch this structure, rearrange irqfd fields to make fastpath better packed for better cache utilization. This also adds some comments about locking rules and rcu usage in code. Some notes on the design: - Use pointer into the rt instead of copying an entry, to make it possible to use rcu, thus side-stepping locking complexities. We also save some memory this way. - Old workqueue code is still used for level irqs. I don't think we DTRT with level anyway, however, it seems easier to keep the code around as it has been thought through and debugged, and fix level later than rip out and re-instate it later. Signed-off-by: Michael S. Tsirkin <> Acked-by: Marcelo Tosatti <> Acked-by: Gregory Haskins <> Signed-off-by: Avi Kivity <>
2010-09-23KVM: fix irqfd assign/deassign raceMichael S. Tsirkin
I think I see the following (theoretical) race: During irqfd assign, we drop irqfds lock before we schedule inject work. Therefore, deassign running on another CPU could cause shutdown and flush to run before inject, causing user after free in inject. A simple fix it to schedule inject under the lock. Signed-off-by: Michael S. Tsirkin <> Acked-by: Gregory Haskins <> Signed-off-by: Marcelo Tosatti <>
2010-08-01KVM: Update Red Hat copyrightsAvi Kivity
Signed-off-by: Avi Kivity <>
2010-03-30include cleanup: Update gfp.h and slab.h includes to prepare for breaking ↵Tejun Heo
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. 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 <> Guess-its-ok-by: Christoph Lameter <> Cc: Ingo Molnar <> Cc: Lee Schermerhorn <>
2010-03-01KVM: do not store wqh in irqfdMichael S. Tsirkin
wqh is unused, so we do not need to store it in irqfd anymore Signed-off-by: Michael S. Tsirkin <> Signed-off-by: Avi Kivity <>
2010-03-01KVM: convert slots_lock to a mutexMarcelo Tosatti
Signed-off-by: Marcelo Tosatti <>
2010-03-01KVM: convert io_bus to SRCUMarcelo Tosatti
Signed-off-by: Marcelo Tosatti <>
2010-01-25KVM: fix spurious interrupt with irqfdMichael S. Tsirkin
kvm didn't clear irqfd counter on deassign, as a result we could get a spurious interrupt when irqfd is assigned back. this leads to poor performance and, in theory, guest crash. Signed-off-by: Michael S. Tsirkin <> Signed-off-by: Avi Kivity <>
2010-01-25KVM: only allow one gsi per fdMichael S. Tsirkin
Looks like repeatedly binding same fd to multiple gsi's with irqfd can use up a ton of kernel memory for irqfd structures. A simple fix is to allow each fd to only trigger one gsi: triggering a storm of interrupts in guest is likely useless anyway, and we can do it by binding a single gsi to many interrupts if we really want to. Cc: Signed-off-by: Michael S. Tsirkin <> Acked-by: Acked-by: Gregory Haskins <> Signed-off-by: Avi Kivity <>
2009-12-03KVM: Drop kvm->irq_lock lock from irq injection pathGleb Natapov
The only thing it protects now is interrupt injection into lapic and this can work lockless. Even now with kvm->irq_lock in place access to lapic is not entirely serialized since vcpu access doesn't take kvm->irq_lock. Signed-off-by: Gleb Natapov <> Signed-off-by: Avi Kivity <>
2009-09-10KVM: correct error-handling codeJulia Lawall
This code is not executed before file has been initialized to the result of calling eventfd_fget. This function returns an ERR_PTR value in an error case instead of NULL. Thus the test that file is not NULL is always true. A simplified version of the semantic match that finds this problem is as follows: ( // <smpl> @match exists@ expression x, E; statement S1, S2; @@ x = eventfd_fget(...) ... when != x = E ( * if (x == NULL || ...) S1 else S2 | * if (x == NULL && ...) S1 else S2 ) // </smpl> Signed-off-by: Julia Lawall <> Signed-off-by: Avi Kivity <>
2009-09-10KVM: add ioeventfd supportGregory Haskins
ioeventfd is a mechanism to register PIO/MMIO regions to trigger an eventfd signal when written to by a guest. Host userspace can register any arbitrary IO address with a corresponding eventfd and then pass the eventfd to a specific end-point of interest for handling. Normal IO requires a blocking round-trip since the operation may cause side-effects in the emulated model or may return data to the caller. Therefore, an IO in KVM traps from the guest to the host, causes a VMX/SVM "heavy-weight" exit back to userspace, and is ultimately serviced by qemu's device model synchronously before returning control back to the vcpu. However, there is a subclass of IO which acts purely as a trigger for other IO (such as to kick off an out-of-band DMA request, etc). For these patterns, the synchronous call is particularly expensive since we really only want to simply get our notification transmitted asychronously and return as quickly as possible. All the sychronous infrastructure to ensure proper data-dependencies are met in the normal IO case are just unecessary overhead for signalling. This adds additional computational load on the system, as well as latency to the signalling path. Therefore, we provide a mechanism for registration of an in-kernel trigger point that allows the VCPU to only require a very brief, lightweight exit just long enough to signal an eventfd. This also means that any clients compatible with the eventfd interface (which includes userspace and kernelspace equally well) can now register to be notified. The end result should be a more flexible and higher performance notification API for the backend KVM hypervisor and perhipheral components. To test this theory, we built a test-harness called "doorbell". This module has a function called "doorbell_ring()" which simply increments a counter for each time the doorbell is signaled. It supports signalling from either an eventfd, or an ioctl(). We then wired up two paths to the doorbell: One via QEMU via a registered io region and through the doorbell ioctl(). The other is direct via ioeventfd. You can download this test harness here: The measured results are as follows: qemu-mmio: 110000 iops, 9.09us rtt ioeventfd-mmio: 200100 iops, 5.00us rtt ioeventfd-pio: 367300 iops, 2.72us rtt I didn't measure qemu-pio, because I have to figure out how to register a PIO region with qemu's device model, and I got lazy. However, for now we can extrapolate based on the data from the NULLIO runs of +2.56us for MMIO, and -350ns for HC, we get: qemu-pio: 153139 iops, 6.53us rtt ioeventfd-hc: 412585 iops, 2.37us rtt these are just for fun, for now, until I can gather more data. Here is a graph for your convenience: The conclusion to draw is that we save about 4us by skipping the userspace hop. -------------------- Signed-off-by: Gregory Haskins <> Acked-by: Michael S. Tsirkin <> Signed-off-by: Avi Kivity <>
2009-09-10KVM: switch irq injection/acking data structures to irq_lockMarcelo Tosatti
Protect irq injection/acking data structures with a separate irq_lock mutex. This fixes the following deadlock: CPU A CPU B kvm_vm_ioctl_deassign_dev_irq() mutex_lock(&kvm->lock); worker_thread() -> kvm_deassign_irq() -> kvm_assigned_dev_interrupt_work_handler() -> deassign_host_irq() mutex_lock(&kvm->lock); -> cancel_work_sync() [blocked] [gleb: fix ia64 path] Reported-by: Alex Williamson <> Signed-off-by: Marcelo Tosatti <> Signed-off-by: Gleb Natapov <> Signed-off-by: Avi Kivity <>
2009-09-10KVM: irqfdGregory Haskins
KVM provides a complete virtual system environment for guests, including support for injecting interrupts modeled after the real exception/interrupt facilities present on the native platform (such as the IDT on x86). Virtual interrupts can come from a variety of sources (emulated devices, pass-through devices, etc) but all must be injected to the guest via the KVM infrastructure. This patch adds a new mechanism to inject a specific interrupt to a guest using a decoupled eventfd mechnanism: Any legal signal on the irqfd (using eventfd semantics from either userspace or kernel) will translate into an injected interrupt in the guest at the next available interrupt window. Signed-off-by: Gregory Haskins <> Signed-off-by: Avi Kivity <>