mirror of
https://github.com/hanzoai/visor.git
synced 2026-09-24 17:04:14 +00:00
Tianyu Zhou
fc1afc9de5
SlimVM is a lightweight VMX-based platform for gVisor that accelerates sentry system calls by eliminating unnecessary user/kernel context switches. In a traditional gVisor + KVM setup, every guest syscall triggers a full VM exit to userspace, then re-enters the kernel via a regular syscall: gr0 -> hr0 (vm_exit) -> hr3 (ioctl return) -> hr0 (re-invoke syscall) SlimVM eliminates this overhead. When the guest executes a VMCALL, the VM exits into VMX root mode where SlimVM directly invokes the host kernel's syscall handler, then immediately resumes the guest: gr0 -> hr0 (vmcall + direct function call) SlimVM requires a companion kernel module that provides the /dev/slimvm device interface. See https://github.com/antgroup/slimvm for the kernel module and full documentation. A sentry->host getpid microbenchmark (Xeon 6982P-C, host kernel 5.10.134) shows the effect: │ ns/op │ vs base │ base 82.5 1.0x slimvm 420.9 5.1x kvm 3566.1 43.2x slimvm is ~8.5x faster than the kvm platform on this path. See the issue for details. Updates: https://github.com/google/gvisor/issues/13330 Co-developed-by: Chenggang <[email protected]> Co-developed-by: Robin Luk <[email protected]> Co-developed-by: Tiwei Bie <[email protected]> Co-developed-by: Jianfeng Tan <[email protected]> Co-developed-by: liushi.ls <[email protected]> Co-developed-by: Yong He <[email protected]> Co-developed-by: Aaron Lu <[email protected]> Co-developed-by: chris.zn <[email protected]> Co-developed-by: Lai Jiangshan <[email protected]> Co-developed-by: Lingfu <[email protected]> Co-developed-by: Min Le <[email protected]> Co-developed-by: Quan Xu <[email protected]> Co-developed-by: Zhang Haoyu <[email protected]> Co-developed-by: Dawei Shen <[email protected]> Signed-off-by: Tianyu Zhou <[email protected]>
71 lines
2.1 KiB
Go
71 lines
2.1 KiB
Go
// Copyright 2026 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package slimvm
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import (
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"fmt"
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"syscall"
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"gvisor.dev/gvisor/pkg/hostsyscall"
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"gvisor.dev/gvisor/pkg/ring0"
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"gvisor.dev/gvisor/pkg/sighandling"
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)
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var (
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// bounceSignal is the signal used for bouncing the vCPU.
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//
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// We use SIGCHLD because it is not masked by the runtime, and
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// it will be ignored properly by other parts of the kernel.
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bounceSignal = syscall.SIGCHLD
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// bounce is the interrupt vector used to return to the kernel.
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bounce = uint32(ring0.VirtualizationException)
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// savedHandler is a pointer to the previous handler.
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//
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// This is called by bluepillHandler.
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savedHandler uintptr
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)
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// bluepill enters guest mode.
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func bluepill(*vCPU)
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// sighandler is the signal entry point.
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func sighandler()
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// Return the start address of the functions above.
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//
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// In Go 1.17+, Go references to assembly functions resolve to an ABIInternal
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// wrapper function rather than the function itself. We must reference from
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// assembly to get the ABI0 (i.e., primary) address.
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func addrOfSighandler() uintptr
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// redpillSyscall is syscall -1, used by SlimVM to transition to host.
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const redpillSyscall = ^uintptr(0)
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// redpill on amd64/arm64 invokes a syscall with -1.
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//
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//go:nosplit
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func redpill() {
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hostsyscall.RawSyscallErrno(redpillSyscall, 0, 0, 0)
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}
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func saveSignalHandler() {
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// Install the handler.
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if err := sighandling.ReplaceSignalHandler(bluepillSignal, addrOfSighandler(), &savedHandler); err != nil {
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panic(fmt.Sprintf("Unable to set handler for signal %d: %v", bluepillSignal, err))
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}
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}
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