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qemu: tcg: use max by default #3487

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Merged
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May 2, 2025
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qemu: tcg: use max by default #3487

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47 changes: 24 additions & 23 deletions pkg/limayaml/defaults.go
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Original file line number Diff line number Diff line change
Expand Up @@ -61,34 +61,40 @@ var (
)

func defaultCPUType() CPUType {
// x86_64 + TCG + max was previously unstable until 2021.
// https://bugzilla.redhat.com/show_bug.cgi?id=1999700
// https://bugs.launchpad.net/qemu/+bug/1748296
defaultX8664 := "max"
if runtime.GOOS == "windows" && runtime.GOARCH == "amd64" {
// https://github.com/lima-vm/lima/pull/3487#issuecomment-2846253560
// > #931 intentionally prevented the code from setting it to max when running on Windows,
// > and kept it at qemu64.
//
// TODO: remove this if "max" works with the latest qemu
defaultX8664 = "qemu64"
}
cpuType := map[Arch]string{
AARCH64: "cortex-a76", // available since QEMU 7.1 (Aug 2022)
ARMV7L: "cortex-a7",
// Since https://github.com/lima-vm/lima/pull/494, we use qemu64 cpu for better emulation of x86_64.
X8664: "qemu64",
AARCH64: "max",
ARMV7L: "max",
X8664: defaultX8664,
RISCV64: "max",
S390X: "qemu", // FIXME: what is the right choice for s390x?
S390X: "max",
}
for arch := range cpuType {
if IsNativeArch(arch) && IsAccelOS() {
if HasHostCPU() {
cpuType[arch] = "host"
} else if HasMaxCPU() {
cpuType[arch] = "max"
}
}
if arch == X8664 && runtime.GOOS == "darwin" {
switch cpuType[arch] {
case "host", "max":
// disable AVX-512, since it requires trapping instruction faults in guest
// Enterprise Linux requires either v2 (SSE4) or v3 (AVX2), but not yet v4.
cpuType[arch] += ",-avx512vl"

// Disable pdpe1gb on Intel Mac
// https://github.com/lima-vm/lima/issues/1485
// https://stackoverflow.com/a/72863744/5167443
cpuType[arch] += ",-pdpe1gb"
}
// disable AVX-512, since it requires trapping instruction faults in guest
// Enterprise Linux requires either v2 (SSE4) or v3 (AVX2), but not yet v4.
cpuType[arch] += ",-avx512vl"

// Disable pdpe1gb on Intel Mac
// https://github.com/lima-vm/lima/issues/1485
// https://stackoverflow.com/a/72863744/5167443
cpuType[arch] += ",-pdpe1gb"
}
}
return cpuType
Expand Down Expand Up @@ -1273,11 +1279,6 @@ func HasHostCPU() bool {
return false
}

func HasMaxCPU() bool {
// windows: WHPX: Unexpected VP exit code 4
return HasHostCPU()
}

func IsNativeArch(arch Arch) bool {
nativeX8664 := arch == X8664 && runtime.GOARCH == "amd64"
nativeAARCH64 := arch == AARCH64 && runtime.GOARCH == "arm64"
Expand Down
7 changes: 4 additions & 3 deletions pkg/qemu/qemu.go
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Expand Up @@ -548,7 +548,8 @@ func Cmdline(ctx context.Context, cfg Config) (exe string, args []string, err er
// Machine
switch *y.Arch {
case limayaml.X8664:
if strings.HasPrefix(cpu, "qemu64") && runtime.GOOS != "windows" {
switch accel {
case "tcg":
// use q35 machine with vmware io port disabled.
args = appendArgsIfNoConflict(args, "-machine", "q35,vmport=off")
// use tcg accelerator with multi threading with 512MB translation block size
Expand All @@ -559,10 +560,10 @@ func Cmdline(ctx context.Context, cfg Config) (exe string, args []string, err er
// This will disable CPU S3/S4 state.
args = append(args, "-global", "ICH9-LPC.disable_s3=1")
args = append(args, "-global", "ICH9-LPC.disable_s4=1")
} else if runtime.GOOS == "windows" && accel == "whpx" {
case "whpx":
// whpx: injection failed, MSI (0, 0) delivery: 0, dest_mode: 0, trigger mode: 0, vector: 0
args = appendArgsIfNoConflict(args, "-machine", "q35,accel="+accel+",kernel-irqchip=off")
} else {
default:
args = appendArgsIfNoConflict(args, "-machine", "q35,accel="+accel)
}
case limayaml.AARCH64:
Expand Down
6 changes: 0 additions & 6 deletions templates/_images/centos-stream-10.yaml
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Expand Up @@ -28,9 +28,3 @@ firmware:
# CentOS Stream 10 still requires legacyBIOS
# https://issues.redhat.com/browse/CS-2672
legacyBIOS: true

cpuType:
# When emulating Intel on ARM hosts, Lima uses the "qemu64" CPU by default (https://github.com/lima-vm/lima/pull/494).
# However, CentOS Stream 10 kernel reboots indefinitely due to lack of the support for x86_64-v3 instructions.
# This issue is tracked in <https://github.com/lima-vm/lima/issues/3063>.
x86_64: "Haswell-v4"
8 changes: 4 additions & 4 deletions templates/default.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -334,10 +334,10 @@ os: null
# Setting of instructions is supported like this: "qemu64,+ssse3".
# 🟢 Builtin default: hard-coded arch map with type (see the output of `limactl info | jq .defaultTemplate.cpuType`)
cpuType:
# aarch64: "cortex-a76" # (or "host" when running on aarch64 host)
# armv7l: "cortex-a7" # (or "host" when running on armv7l host)
# riscv64: "rv64" # (or "host" when running on riscv64 host)
# x86_64: "qemu64" # (or "host,-pdpe1gb" when running on x86_64 host)
# aarch64: "max" # (or "host" when running on aarch64 host)
# armv7l: "max" # (or "host" when running on armv7l host)
# riscv64: "max" # (or "host" when running on riscv64 host)
# x86_64: "max" # (or "host" when running on x86_64 host; additional options are appended on Intel Mac)

rosetta:
# Enable Rosetta inside the VM; needs `vmType: vz`
Expand Down
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