Running docker-in-docker with QEMU emulation produces some noisy errors

[thaJeztah]

NOTE: perhaps there's an existing issue for this already (I need to search), but posting the information in case we need it later 😂

For testing, I just started a dind container using --platform=linux/arm64 (on Docker Desktop, running on an Intel machine). This runs the container with QEMU to allow running containers with a non-matching architecture (on a "best effort" base).

docker run -it --rm --privileged -v /var/lib/docker --platform=linux/arm64 docker:dind --iptables=false

When doing so, multiple errors are printed, both in the daemon logs during startup, as well as when (e.g.) running docker version or docker info;

ERRO[0000] failure getting variant                       error="getCPUInfo for pattern: Cpu architecture: not found"

So, generally, this is somewhat expected, but wondering if we;

• can (should?) make this less noisy
• could we detect the "emulation" and produce more "correct" information?
• perhaps perform this only once during the daemon's lifecycle (instead of trying to parse (and error) multiple times (this is somewhat separate from the error itself, but perhaps a sync.Once wouldn't hurt for this).

In case we want to write a test for this, here's the output of /proc/cpuinfo;

cat /proc/cpuinfo
processor	: 0
vendor_id	: GenuineIntel
cpu family	: 6
model		: 60
model name	: Intel(R) Core(TM) i7-4790K CPU @ 4.00GHz
stepping	: 3
cpu MHz		: 3987.822
cache size	: 8192 KB
physical id	: 0
siblings	: 1
core id		: 0
cpu cores	: 1
apicid		: 0
initial apicid	: 0
fpu		: yes
fpu_exception	: yes
cpuid level	: 13
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss ht pbe syscall nx pdpe1gb lm constant_tsc rep_good nopl xtopology nonstop_tsc cpuid pni pclmulqdq dtes64 ds_cpl ssse3 sdbg fma cx16 xtpr pcid sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand hypervisor lahf_lm abm fsgsbase bmi1 avx2 bmi2 erms xsaveopt arat
bugs		: cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds swapgs itlb_multihit srbds
bogomips	: 7975.64
clflush size	: 64
cache_alignment	: 64
address sizes	: 39 bits physical, 48 bits virtual
power management:

processor	: 1
vendor_id	: GenuineIntel
cpu family	: 6
model		: 60
model name	: Intel(R) Core(TM) i7-4790K CPU @ 4.00GHz
stepping	: 3
cpu MHz		: 3987.822
cache size	: 8192 KB
physical id	: 1
siblings	: 1
core id		: 0
cpu cores	: 1
apicid		: 1
initial apicid	: 1
fpu		: yes
fpu_exception	: yes
cpuid level	: 13
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss ht pbe syscall nx pdpe1gb lm constant_tsc rep_good nopl xtopology nonstop_tsc cpuid pni pclmulqdq dtes64 ds_cpl ssse3 sdbg fma cx16 xtpr pcid sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand hypervisor lahf_lm abm fsgsbase bmi1 avx2 bmi2 erms xsaveopt arat
bugs		: cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds swapgs itlb_multihit srbds
bogomips	: 7950.24
clflush size	: 64
cache_alignment	: 64
address sizes	: 39 bits physical, 48 bits virtual
power management:

processor	: 2
vendor_id	: GenuineIntel
cpu family	: 6
model		: 60
model name	: Intel(R) Core(TM) i7-4790K CPU @ 4.00GHz
stepping	: 3
cpu MHz		: 3987.822
cache size	: 8192 KB
physical id	: 2
siblings	: 1
core id		: 0
cpu cores	: 1
apicid		: 2
initial apicid	: 2
fpu		: yes
fpu_exception	: yes
cpuid level	: 13
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss ht pbe syscall nx pdpe1gb lm constant_tsc rep_good nopl xtopology nonstop_tsc cpuid pni pclmulqdq dtes64 ds_cpl ssse3 sdbg fma cx16 xtpr pcid sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand hypervisor lahf_lm abm fsgsbase bmi1 avx2 bmi2 erms xsaveopt arat
bugs		: cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds swapgs itlb_multihit srbds
bogomips	: 8054.40
clflush size	: 64
cache_alignment	: 64
address sizes	: 39 bits physical, 48 bits virtual
power management:

processor	: 3
vendor_id	: GenuineIntel
cpu family	: 6
model		: 60
model name	: Intel(R) Core(TM) i7-4790K CPU @ 4.00GHz
stepping	: 3
cpu MHz		: 3987.822
cache size	: 8192 KB
physical id	: 3
siblings	: 1
core id		: 0
cpu cores	: 1
apicid		: 3
initial apicid	: 3
fpu		: yes
fpu_exception	: yes
cpuid level	: 13
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss ht pbe syscall nx pdpe1gb lm constant_tsc rep_good nopl xtopology nonstop_tsc cpuid pni pclmulqdq dtes64 ds_cpl ssse3 sdbg fma cx16 xtpr pcid sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand hypervisor lahf_lm abm fsgsbase bmi1 avx2 bmi2 erms xsaveopt arat
bugs		: cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds swapgs itlb_multihit srbds
bogomips	: 7845.03
clflush size	: 64
cache_alignment	: 64
address sizes	: 39 bits physical, 48 bits virtual
power management:

[thaJeztah]

And... just realised this code is coming from containerd's platforms package, so may need fixing there;

moby/vendor/github.com/containerd/containerd/platforms/cpuinfo.go

Line 78 in 2c97295

return "", errors.Wrapf(errdefs.ErrNotFound, "getCPUInfo for pattern: %s", pattern)

The sync.Once could possibly be on our side though (although it already has one for "variant";

moby/vendor/github.com/containerd/containerd/platforms/cpuinfo.go

Lines 37 to 44 in 2c97295

	func cpuVariant() string {
	cpuVariantOnce.Do(func() {
	if isArmArch(runtime.GOARCH) {
	cpuVariantValue = getCPUVariant()
	}
	})
	return cpuVariantValue
	}

[thaJeztah]

related to / addressed by:

• Fix cpu architecture detection issue on linux/arm containerd/containerd#7636
• [release/1.6] Fix cpu architecture detection issue on emulated ARM platform containerd/containerd#8533