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JackThomson2 merged 2 commits into from
Apr 23, 2026
Merged

Update CPU feature expectations for kernel 6.18 #5851

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test: Update CPU features host-vs-guest expectations for kernel 6.18
JackThomson2 Apr 21, 2026
ad263be
Merge branch 'main' into feat/6_18_updates
JackThomson2 Apr 23, 2026
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103 changes: 78 additions & 25 deletions tests/integration_tests/functional/test_cpu_features_host_vs_guest.py
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Original file line number Diff line number Diff line change
Expand Up @@ -137,6 +137,13 @@
"sme",
} | {"brs", "rapl", "v_spec_ctrl"}

# Since v6.11, flags declared in cpufeatures.h without a quoted /proc/cpuinfo name
# are hidden. VMSCAPE added IBPB_EXIT_TO_USER without one, so v6.18+ amzn2023 hides it.
# https://github.com/torvalds/linux/commit/78ce84b9e0a54a0c91a7449f321c1f852c0cd3fc
AMD_MILAN_HOST_ONLY_FEATS_6_18 = AMD_MILAN_HOST_ONLY_FEATS_6_1 - {
"ibpb_exit_to_user",
} | {"xtopology", "debug_swap"}

AMD_GENOA_HOST_ONLY_FEATS = AMD_MILAN_HOST_ONLY_FEATS | {
"avic",
"flush_l1d",
Expand All @@ -153,6 +160,56 @@
"x2avic",
}

AMD_GENOA_HOST_ONLY_FEATS_6_18 = AMD_GENOA_HOST_ONLY_FEATS_6_1 - {
# Since v6.11, flags declared in cpufeatures.h without a quoted /proc/cpuinfo name
# are hidden. VMSCAPE added IBPB_EXIT_TO_USER without one, so v6.18+ amzn2023 hides it.
# https://github.com/torvalds/linux/commit/78ce84b9e0a54a0c91a7449f321c1f852c0cd3fc
"ibpb_exit_to_user",
# Propagated to the guest since:
# https://github.com/torvalds/linux/commit/8c19b6f257fa (KVM AUTOIBRS, v6.3)
# https://github.com/torvalds/linux/commit/e7862eda309e (guest synthesises ibrs_enhanced
# from AUTOIBRS, v6.3; backported to 5.10 and 6.1 LTSs, so our guest kernels pick it up)
"ibrs_enhanced",
# Propagated to the guest since:
# https://github.com/torvalds/linux/commit/45cf86f26148 (KVM advertises FLUSH_L1D, v6.2)
# https://github.com/torvalds/linux/commit/da3db168fb67 (KVM virtualises MSR_IA32_FLUSH_CMD on SVM, v6.4)
"flush_l1d",
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} | {"debug_swap", "cpuid_fault", "xtopology", "la57", "vnmi"}

INTEL_SPR_GNR_HOST_ONLY_FEATS_6_18_REMOVED = {
# Since v6.11, flags declared in cpufeatures.h without a quoted /proc/cpuinfo name
# are hidden. VMSCAPE added IBPB_EXIT_TO_USER without one, so v6.18+ amzn2023 hides it.
# https://github.com/torvalds/linux/commit/78ce84b9e0a54a0c91a7449f321c1f852c0cd3fc
"ibpb_exit_to_user",
"pebs",
# Propagated to the guest since:
# https://github.com/torvalds/linux/commit/45cf86f26148 (KVM advertises FLUSH_L1D, v6.2)
"flush_l1d",
"dts",
"dtes64",
"bts",
}
INTEL_SPR_GNR_HOST_ONLY_FEATS_6_18_ADDED = {"la57"}

# Intel Ice Lake is not vulnerable to VMScape (BHB clearing software mitigation), so
# "ibpb_exit_to_user" is not needed.
# https://docs.kernel.org/admin-guide/hw-vuln/vmscape.html#affected-processors
INTEL_ICELAKE_HOST_ONLY_FEATS_5_10 = INTEL_HOST_ONLY_FEATS - {
"ibpb_exit_to_user",
"cdp_l3",
} | {"pconfig", "tme", "split_lock_detect"}

INTEL_ICELAKE_HOST_ONLY_FEATS_6_1 = INTEL_ICELAKE_HOST_ONLY_FEATS_5_10 - {
"bts",
"dtes64",
"dts",
"pebs",
}

INTEL_ICELAKE_HOST_ONLY_FEATS_6_18 = INTEL_ICELAKE_HOST_ONLY_FEATS_6_1 - {
"flush_l1d",
} | {"la57"}


def test_host_vs_guest_cpu_features(uvm_plain_any):
"""Check CPU features host vs guest"""
Expand All @@ -169,16 +226,20 @@ def test_host_vs_guest_cpu_features(uvm_plain_any):
case CpuModel.AMD_MILAN:
if global_props.host_linux_version_tpl < (6, 1):
assert host_feats - guest_feats == AMD_MILAN_HOST_ONLY_FEATS
else:
elif global_props.host_linux_version_tpl < (6, 18):
assert host_feats - guest_feats == AMD_MILAN_HOST_ONLY_FEATS_6_1
else:
assert host_feats - guest_feats == AMD_MILAN_HOST_ONLY_FEATS_6_18

assert guest_feats - host_feats == AMD_GUEST_ONLY_FEATS

case CpuModel.AMD_GENOA:
if global_props.host_linux_version_tpl < (6, 1):
assert host_feats - guest_feats == AMD_GENOA_HOST_ONLY_FEATS
else:
elif global_props.host_linux_version_tpl < (6, 18):
assert host_feats - guest_feats == AMD_GENOA_HOST_ONLY_FEATS_6_1
else:
assert host_feats - guest_feats == AMD_GENOA_HOST_ONLY_FEATS_6_18

assert guest_feats - host_feats == AMD_GUEST_ONLY_FEATS

Expand All @@ -189,7 +250,11 @@ def test_host_vs_guest_cpu_features(uvm_plain_any):
# Ubuntu hasn't backported the patch for VMScape yet.
# This is only requried for Intel Cascade Lake since we only run
# tests on Intel Cascade Lake for Ubuntu.
if "amzn" not in global_props.host_os:
# Since v6.11, flags declared in cpufeatures.h without a quoted /proc/cpuinfo name
# are hidden. VMSCAPE added IBPB_EXIT_TO_USER without one, so v6.18+ amzn2023 hides it.
# https://github.com/torvalds/linux/commit/78ce84b9e0a54a0c91a7449f321c1f852c0cd3fc
host_version = global_props.host_linux_version_tpl
if "amzn" not in global_props.host_os or host_version >= (6, 18):
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expected_host_minus_guest -= {"ibpb_exit_to_user"}

# Linux kernel v6.4+ passes through the CPUID bit for "flush_l1d" to guests.
Expand All @@ -214,29 +279,13 @@ def test_host_vs_guest_cpu_features(uvm_plain_any):
assert guest_feats - host_feats == expected_guest_minus_host

case CpuModel.INTEL_ICELAKE:
expected_host_minus_guest = INTEL_HOST_ONLY_FEATS

# As long as BHB clearing software mitigation is enabled, Intel Ice Lake is not
# vulnerable to VMScape and "IBPB before exit to userspace" is not needed.
# https://docs.kernel.org/admin-guide/hw-vuln/vmscape.html#affected-processors
expected_host_minus_guest -= {"ibpb_exit_to_user"}

host_guest_diff_5_10 = expected_host_minus_guest - {"cdp_l3"} | {
"pconfig",
"tme",
"split_lock_detect",
}
host_guest_diff_6_1 = host_guest_diff_5_10 - {
"bts",
"dtes64",
"dts",
"pebs",
}

if global_props.host_linux_version_tpl < (6, 1):
assert host_feats - guest_feats == host_guest_diff_5_10
host_version = global_props.host_linux_version_tpl
if host_version < (6, 1):
assert host_feats - guest_feats == INTEL_ICELAKE_HOST_ONLY_FEATS_5_10
elif host_version < (6, 18):
assert host_feats - guest_feats == INTEL_ICELAKE_HOST_ONLY_FEATS_6_1
else:
assert host_feats - guest_feats == host_guest_diff_6_1
assert host_feats - guest_feats == INTEL_ICELAKE_HOST_ONLY_FEATS_6_18
assert guest_feats - host_feats == INTEL_GUEST_ONLY_FEATS - {"umip"}
case CpuModel.INTEL_SAPPHIRE_RAPIDS | CpuModel.INTEL_GRANITE_RAPIDS:
expected_host_minus_guest = INTEL_HOST_ONLY_FEATS.copy()
Expand Down Expand Up @@ -359,6 +408,10 @@ def test_host_vs_guest_cpu_features(uvm_plain_any):
"tsc_known_freq",
}

if host_version >= (6, 18):
expected_host_minus_guest -= INTEL_SPR_GNR_HOST_ONLY_FEATS_6_18_REMOVED
expected_host_minus_guest |= INTEL_SPR_GNR_HOST_ONLY_FEATS_6_18_ADDED

assert host_feats - guest_feats == expected_host_minus_guest
assert guest_feats - host_feats == expected_guest_minus_host
case CpuModel.ARM_NEOVERSE_N1:
Expand Down
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