128 lines
4.6 KiB
Diff
128 lines
4.6 KiB
Diff
From 2872c423fa44dcbf50b581a5c3feac064a0473a0 Mon Sep 17 00:00:00 2001
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From: Michael Roth <michael.roth@amd.com>
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Date: Tue, 9 Apr 2024 18:07:41 -0500
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Subject: [PATCH 024/100] i386/sev: Add 'legacy-vm-type' parameter for SEV
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guest objects
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RH-Author: Paolo Bonzini <pbonzini@redhat.com>
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RH-MergeRequest: 245: SEV-SNP support
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RH-Jira: RHEL-39544
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RH-Acked-by: Thomas Huth <thuth@redhat.com>
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RH-Acked-by: Bandan Das <bdas@redhat.com>
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RH-Acked-by: Vitaly Kuznetsov <vkuznets@redhat.com>
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RH-Commit: [24/91] ce35d1b09fe8aa8772ff149543f7760455c1e6b5 (bonzini/rhel-qemu-kvm)
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QEMU will currently automatically make use of the KVM_SEV_INIT2 API for
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initializing SEV and SEV-ES guests verses the older
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KVM_SEV_INIT/KVM_SEV_ES_INIT interfaces.
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However, the older interfaces will silently avoid sync'ing FPU/XSAVE
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state to the VMSA prior to encryption, thus relying on behavior and
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measurements that assume the related fields to be allow zero.
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With KVM_SEV_INIT2, this state is now synced into the VMSA, resulting in
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measurements changes and, theoretically, behaviorial changes, though the
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latter are unlikely to be seen in practice.
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To allow a smooth transition to the newer interface, while still
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providing a mechanism to maintain backward compatibility with VMs
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created using the older interfaces, provide a new command-line
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parameter:
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-object sev-guest,legacy-vm-type=true,...
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and have it default to false.
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Signed-off-by: Michael Roth <michael.roth@amd.com>
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Message-ID: <20240409230743.962513-2-michael.roth@amd.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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(cherry picked from commit 023267334da375226720e62963df9545aa8fc2fd)
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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---
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qapi/qom.json | 11 ++++++++++-
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target/i386/sev.c | 18 +++++++++++++++++-
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2 files changed, 27 insertions(+), 2 deletions(-)
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diff --git a/qapi/qom.json b/qapi/qom.json
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index 85e6b4f84a..38dde6d785 100644
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--- a/qapi/qom.json
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+++ b/qapi/qom.json
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@@ -898,6 +898,14 @@
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# designated guest firmware page for measured boot with -kernel
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# (default: false) (since 6.2)
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#
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+# @legacy-vm-type: Use legacy KVM_SEV_INIT KVM interface for creating the VM.
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+# The newer KVM_SEV_INIT2 interface syncs additional vCPU
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+# state when initializing the VMSA structures, which will
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+# result in a different guest measurement. Set this to
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+# maintain compatibility with older QEMU or kernel versions
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+# that rely on legacy KVM_SEV_INIT behavior.
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+# (default: false) (since 9.1)
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+#
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# Since: 2.12
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##
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{ 'struct': 'SevGuestProperties',
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@@ -908,7 +916,8 @@
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'*handle': 'uint32',
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'*cbitpos': 'uint32',
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'reduced-phys-bits': 'uint32',
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- '*kernel-hashes': 'bool' } }
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+ '*kernel-hashes': 'bool',
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+ '*legacy-vm-type': 'bool' } }
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##
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# @ThreadContextProperties:
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diff --git a/target/i386/sev.c b/target/i386/sev.c
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index 9dab4060b8..f4ee317cb0 100644
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--- a/target/i386/sev.c
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+++ b/target/i386/sev.c
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@@ -67,6 +67,7 @@ struct SevGuestState {
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uint32_t cbitpos;
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uint32_t reduced_phys_bits;
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bool kernel_hashes;
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+ bool legacy_vm_type;
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/* runtime state */
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uint32_t handle;
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@@ -356,6 +357,16 @@ static void sev_guest_set_kernel_hashes(Object *obj, bool value, Error **errp)
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sev->kernel_hashes = value;
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}
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+static bool sev_guest_get_legacy_vm_type(Object *obj, Error **errp)
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+{
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+ return SEV_GUEST(obj)->legacy_vm_type;
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+}
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+
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+static void sev_guest_set_legacy_vm_type(Object *obj, bool value, Error **errp)
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+{
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+ SEV_GUEST(obj)->legacy_vm_type = value;
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+}
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+
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bool
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sev_enabled(void)
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{
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@@ -863,7 +874,7 @@ static int sev_kvm_type(X86ConfidentialGuest *cg)
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}
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kvm_type = (sev->policy & SEV_POLICY_ES) ? KVM_X86_SEV_ES_VM : KVM_X86_SEV_VM;
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- if (kvm_is_vm_type_supported(kvm_type)) {
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+ if (kvm_is_vm_type_supported(kvm_type) && !sev->legacy_vm_type) {
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sev->kvm_type = kvm_type;
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} else {
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sev->kvm_type = KVM_X86_DEFAULT_VM;
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@@ -1381,6 +1392,11 @@ sev_guest_class_init(ObjectClass *oc, void *data)
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sev_guest_set_kernel_hashes);
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object_class_property_set_description(oc, "kernel-hashes",
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"add kernel hashes to guest firmware for measured Linux boot");
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+ object_class_property_add_bool(oc, "legacy-vm-type",
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+ sev_guest_get_legacy_vm_type,
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+ sev_guest_set_legacy_vm_type);
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+ object_class_property_set_description(oc, "legacy-vm-type",
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+ "use legacy VM type to maintain measurement compatibility with older QEMU or kernel versions.");
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}
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static void
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--
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2.39.3
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