This is a note to let you know that I've just added the patch titled
SEV: disable SEV-ES DebugSwap by default
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sev-disable-sev-es-debugswap-by-default.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 5abf6dceb066f2b02b225fd561440c98a8062681 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Date: Sat, 9 Mar 2024 11:24:58 -0500
Subject: SEV: disable SEV-ES DebugSwap by default
From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/svm/sev.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index a132547fcfb5..a8ce5226b3b5 100644
--- 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_svm *svm)
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);
--
2.44.0
Patches currently in stable-queue which might be from pbonzini@xxxxxxxxxx are
queue-6.6/kvm-svm-flush-pages-under-kvm-lock-to-fix-uaf-in-svm_register_enc_region.patch
queue-6.6/sev-disable-sev-es-debugswap-by-default.patch
