6.7-stable review patch. If anyone has any objections, please let me know.
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From: Paolo Bonzini pbonzini@redhat.com
commit 5abf6dceb066f2b02b225fd561440c98a8062681 upstream.
The DebugSwap feature of SEV-ES provides a way for confidential guests to use data breakpoints. However, because the status of the DebugSwap feature is recorded in the VMSA, enabling it by default invalidates the attestation signatures. In 6.10 we will introduce a new API to create SEV VMs that will allow enabling DebugSwap based on what the user tells KVM to do. Contextually, we will change the legacy KVM_SEV_ES_INIT API to never enable DebugSwap.
For compatibility with kernels that pre-date the introduction of DebugSwap, as well as with those where KVM_SEV_ES_INIT will never enable it, do not enable the feature by default. If anybody wants to use it, for now they can enable the sev_es_debug_swap_enabled module parameter, but this will result in a warning.
Fixes: d1f85fbe836e ("KVM: SEV: Enable data breakpoints in SEV-ES") Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/svm/sev.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
--- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -57,7 +57,7 @@ static bool sev_es_enabled = true; module_param_named(sev_es, sev_es_enabled, bool, 0444);
/* enable/disable SEV-ES DebugSwap support */ -static bool sev_es_debug_swap_enabled = true; +static bool sev_es_debug_swap_enabled = false; module_param_named(debug_swap, sev_es_debug_swap_enabled, bool, 0444); #else #define sev_enabled false @@ -612,8 +612,11 @@ static int sev_es_sync_vmsa(struct vcpu_ save->xss = svm->vcpu.arch.ia32_xss; save->dr6 = svm->vcpu.arch.dr6;
- if (sev_es_debug_swap_enabled) + if (sev_es_debug_swap_enabled) { save->sev_features |= SVM_SEV_FEAT_DEBUG_SWAP; + pr_warn_once("Enabling DebugSwap with KVM_SEV_ES_INIT. " + "This will not work starting with Linux 6.10\n"); + }
pr_debug("Virtual Machine Save Area (VMSA):\n"); print_hex_dump_debug("", DUMP_PREFIX_NONE, 16, 1, save, sizeof(*save), false);