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]>
77 lines
1.6 KiB
Go
77 lines
1.6 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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//go:build amd64
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// +build amd64
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package slimvm
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import (
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"sync"
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"gvisor.dev/gvisor/pkg/atomicbitops"
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)
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const (
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limitPCID = 4096
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fixedKernelPCID = 1
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)
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var (
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pcidCache []uint16
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pcidMu sync.Mutex
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)
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type pcidBitmap [(limitPCID + 64 - 1) / 64]atomicbitops.Uint64
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func (bm *pcidBitmap) set(pcid uint16) {
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atomicbitops.OrUint64(&bm[pcid/64], 1<<(pcid%64))
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}
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func (bm *pcidBitmap) clear(pcid uint16) {
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atomicbitops.AndUint64(&bm[pcid/64], ^(1 << (pcid % 64)))
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}
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func (bm *pcidBitmap) test(pcid uint16) bool {
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return bm[pcid/64].Load()&(1<<(pcid%64)) != 0
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}
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func initPCIDs() {
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if !hasGuestPCID {
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return
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}
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for pcid := fixedKernelPCID + 1; pcid < limitPCID; pcid++ {
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pcidCache = append(pcidCache, uint16(pcid))
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}
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}
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func assignPCID(pcid *uint16) uint16 {
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pcidMu.Lock()
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if *pcid == 0 && len(pcidCache) > 0 {
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*pcid = pcidCache[len(pcidCache)-1]
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pcidCache = pcidCache[:len(pcidCache)-1]
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}
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pcidMu.Unlock()
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return *pcid
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}
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func dropPCID(pcid uint16) {
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if pcid == 0 {
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return
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}
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pcidMu.Lock()
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pcidCache = append(pcidCache, pcid)
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pcidMu.Unlock()
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}
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