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image-index: Document Linux cpuinfo flags (on x86) for platform.features #631

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image-index: Document Linux cpuinfo flags (on x86) for platform.features #631

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14 changes: 11 additions & 3 deletions image-index.md
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Original file line number Diff line number Diff line change
Expand Up @@ -67,7 +67,13 @@ For the media type(s) that this document is compatible with, see the [matrix][ma

- **`features`** *array of strings*

This OPTIONAL property specifies an array of strings, each specifying a mandatory CPU feature (for example `sse4` or `aes`).
This OPTIONAL property specifies an array of strings, each specifying a mandatory CPU feature.

When `architecture` is `386` or `amd64`, image indexes SHOULD use, and implementations SHOULD understand, values [supported by Linux][cpufeatures.h] with the `X86_FEATURE_` prefix removed and the remainder lowercased.
For example, include `vmx` (for `X86_FEATURE_VMX`) if the image contains an executable compiled to use `VMXON` and related instructions with no fallback.
On Linux on these architectures, the features supported by host CPUs can be found in the `flags` entries in the `cpuinfo` file provided by the [proc filesystem][proc.5].

When `architecture` is neither `386` nor `amd64`, values are implementation-defined and SHOULD be submitted to this specification for standardization.

- **`annotations`** *string-string map*

Expand Down Expand Up @@ -99,8 +105,8 @@ For the media type(s) that this document is compatible with, see the [matrix][ma
"platform": {
"architecture": "amd64",
"os": "linux",
"os.features": [
"sse4"
"features": [
"vmx"
]
}
}
Expand All @@ -112,5 +118,7 @@ For the media type(s) that this document is compatible with, see the [matrix][ma
}
```

[cpufeatures.h]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/x86/include/asm/cpufeatures.h
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For L108 (GitHub doesn't allow me to directly comment there)

  • os.features -> features
  • sse4 -> sse4_2 (please grep and update other files as well)

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Fixed “os.features” → “features” in dc5e4a0 → e1045bf. Also replaced the old sse4 instances, although I replaced them with fpu since I was using fpu and vme since those are the first two entries in cpufeatures.h. I don't really care what features we use as examples though; if there's a strong preference for sse4_2, I can switch to that instead.

[proc.5]: http://man7.org/linux/man-pages/man5/proc.5.html
[runtime-platform2]: https://github.com/opencontainers/runtime-spec/blob/v1.0.0-rc3/config.md#platform
[matrix]: media-types.md#compatibility-matrix
10 changes: 5 additions & 5 deletions schema/imageindex_test.go
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Expand Up @@ -61,7 +61,7 @@ func TestImageIndex(t *testing.T) {
"architecture": "amd64",
"os": "linux",
"features": [
"sse4"
"vmx"
]
}
}
Expand All @@ -84,7 +84,7 @@ func TestImageIndex(t *testing.T) {
"architecture": "amd64",
"os": "linux",
"features": [
"sse4"
"vmx"
]
}
}
Expand Down Expand Up @@ -128,7 +128,7 @@ func TestImageIndex(t *testing.T) {
"architecture": "amd64",
"os": "linux",
"features": [
"sse4"
"vmx"
]
}
}
Expand All @@ -152,7 +152,7 @@ func TestImageIndex(t *testing.T) {
"architecture": "amd64",
"os": "linux",
"features": [
"sse4"
"vmx"
]
}
}
Expand Down Expand Up @@ -185,7 +185,7 @@ func TestImageIndex(t *testing.T) {
"architecture": "amd64",
"os": "linux",
"features": [
"sse4"
"vmx"
]
}
}
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2 changes: 1 addition & 1 deletion specs-go/v1/index.go
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Expand Up @@ -38,7 +38,7 @@ type Platform struct {
Variant string `json:"variant,omitempty"`

// Features is an optional field specifying an array of strings, each
// listing a required CPU feature (for example `sse4` or `aes`).
// listing a required CPU feature.
Features []string `json:"features,omitempty"`
}

Expand Down