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KVM: SVM: Drop the module param to control SEV-ES DebugSwap

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Rip out the DebugSwap module param, as the sequence of events that led to
its inclusion was one big mistake, the param no longer serves any purpose.

Commit d1f85fbe83 ("KVM: SEV: Enable data breakpoints in SEV-ES") goofed
by not adding a way for the userspace VMM to control the feature.
Functionally, that was fine, but it broke attestation signatures because
SEV_FEATURES are included in the signature.

Commit 5abf6dceb0 ("SEV: disable SEV-ES DebugSwap by default") fixed that
issue, but the underlying flaw of userspace not having a way to control
SEV_FEATURES was still there.

That flaw was addressed by commit 4f5defae70 ("KVM: SEV: introduce
KVM_SEV_INIT2 operation"), and so then 4dd5ecacb9 ("KVM: SEV: allow
SEV-ES DebugSwap again") re-enabled DebugSwap by default.

Now that the dust has settled, the module param doesn't serve any
meaningful purpose.

Cc: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://patch.msgid.link/20260109033101.1005769-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2026-01-08 19:31:00 -08:00
parent ca2eccb953
commit 9587dd7a7e
1 changed files with 3 additions and 8 deletions
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11
arch/x86/kvm/svm/sev.c
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@ -53,9 +53,6 @@ module_param_named(sev_es, sev_es_enabled, bool, 0444);
static bool sev_snp_enabled = true;
module_param_named(sev_snp, sev_snp_enabled, bool, 0444);
/* enable/disable SEV-ES DebugSwap support */
static bool sev_es_debug_swap_enabled = true;
module_param_named(debug_swap, sev_es_debug_swap_enabled, bool, 0444);
static u64 sev_supported_vmsa_features;
static unsigned int nr_ciphertext_hiding_asids;
@ -3150,12 +3147,10 @@ void __init sev_hardware_setup(void)
sev_es_enabled = sev_es_supported;
sev_snp_enabled = sev_snp_supported;
if (!sev_es_enabled || !cpu_feature_enabled(X86_FEATURE_DEBUG_SWAP) ||
!cpu_feature_enabled(X86_FEATURE_NO_NESTED_DATA_BP))
sev_es_debug_swap_enabled = false;
sev_supported_vmsa_features = 0;
if (sev_es_debug_swap_enabled)
if (sev_es_enabled && cpu_feature_enabled(X86_FEATURE_DEBUG_SWAP) &&
cpu_feature_enabled(X86_FEATURE_NO_NESTED_DATA_BP))
sev_supported_vmsa_features |= SVM_SEV_FEAT_DEBUG_SWAP;
if (sev_snp_enabled && tsc_khz && cpu_feature_enabled(X86_FEATURE_SNP_SECURE_TSC))