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]>
102 lines
2.6 KiB
ArmAsm
102 lines
2.6 KiB
ArmAsm
// 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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#include "textflag.h"
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// VCPU_CPU is the location of the CPU in the vCPU struct.
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//
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// This is guaranteed to be zero.
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#define VCPU_CPU 0x0
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// ENTRY_CPU_SELF is the location of the CPU in the entry struct.
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//
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// This is sourced from ring0.
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#define ENTRY_CPU_SELF 272 // +checkoffset ring0 kernelEntry.cpuSelf
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// Context offsets.
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//
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// Only limited use of the context is done in the assembly stub below, most is
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// done in the Go handlers. However, the RIP must be examined.
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#define CONTEXT_RAX 0x90
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#define CONTEXT_RIP 0xa8
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#define CONTEXT_FP 0xe0
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// CLI is the literal byte for the disable interrupts instruction.
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//
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// This is checked as the source of the fault.
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#define CLI $0xfa
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// See bluepill.go.
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TEXT ·bluepill(SB),NOSPLIT|NOFRAME,$0
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begin:
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MOVQ arg+0(FP), AX
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LEAQ VCPU_CPU(AX), BX
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// The gorountine stack will be changed in guest which renders
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// the frame pointer outdated and misleads perf tools.
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// Disconnect the frame-chain with the zeroed frame pointer
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// when it is saved in the frame in bluepillHandler().
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MOVQ BP, CX
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MOVQ $0, BP
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BYTE CLI;
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MOVQ CX, BP
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check_vcpu:
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MOVQ ENTRY_CPU_SELF(GS), CX
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CMPQ BX, CX
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JE right_vCPU
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wrong_vcpu:
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CALL ·redpill(SB)
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JMP begin
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right_vCPU:
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RET
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// sighandler: see bluepill.go for documentation.
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//
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// The arguments are the following:
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//
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// DI - The signal number.
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// SI - Pointer to siginfo_t structure.
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// DX - Pointer to ucontext structure.
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//
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TEXT ·sighandler(SB),NOSPLIT|NOFRAME,$0
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// Check if the signal is from the kernel.
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MOVQ $0x80, CX
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CMPL CX, 0x8(SI)
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JNE fallback
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// Check if RIP is disable interrupts.
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MOVQ CONTEXT_RIP(DX), CX
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CMPQ CX, $0x0
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JE fallback
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CMPB 0(CX), CLI
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JNE fallback
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// Call the bluepillHandler.
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PUSHQ DX // First argument (context).
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CALL ·bluepillHandler(SB) // Call the handler.
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POPQ DX // Discard the argument.
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RET
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fallback:
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// Jump to the previous signal handler.
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XORQ CX, CX
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MOVQ ·savedHandler(SB), AX
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JMP AX
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// func addrOfSighandler() uintptr
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TEXT ·addrOfSighandler(SB), $0-8
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MOVQ $·sighandler(SB), AX
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MOVQ AX, ret+0(FP)
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RET
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