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Test guest CET access across KVM kernels #2051

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Merged
jsturtevant merged 1 commit into from
Nov 11, 2026
Merged

Test guest CET access across KVM kernels #2051

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21 changes: 15 additions & 6 deletions src/hyperlight_host/src/sandbox/initialized.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5963,14 +5963,23 @@ mod tests {
"KVM guest CPUID exposes CET shadow stacks"
);

// With CET hidden the host cannot read or write IA32_S_CET, so
// allowing it is rejected at VM creation.
let err = SandboxBuilder::from_file(simple_guest_as_pathbuf())
// Some KVM hosts allow zero-valued CET MSRs without exposing CET to the guest.
let declared = SandboxBuilder::from_file(simple_guest_as_pathbuf())
.guest_msrs(&[MSR_S_CET])
.unwrap()
.build()
.expect_err("allowing IA32_S_CET must be rejected when CET is hidden");
assert_msr_not_declarable(&err, MSR_S_CET);
.build();
match declared {
Ok(mut sbox) => {
const CET_SHSTK_EN: u64 = 1;
let result = sbox.call::<()>("WriteMSR", (MSR_S_CET, CET_SHSTK_EN));
assert!(
matches!(result, Err(HyperlightError::GuestAborted(_, _))),
"expected a guest abort when enabling CET shadow stacks: {result:?}"
);
assert!(sbox.status().is_poisoned());
}
Err(err) => assert_msr_not_declarable(&err, MSR_S_CET),
}
}
}

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