On 2/29/2024 9:25 PM, Markus Armbruster wrote:
Xiaoyao Li <xiaoyao.li@xxxxxxxxx> writes:
On 2/29/2024 4:37 PM, Markus Armbruster wrote:
Xiaoyao Li <xiaoyao.li@xxxxxxxxx> writes:
From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
Three sha384 hash values, mrconfigid, mrowner and mrownerconfig, of a TD
can be provided for TDX attestation. Detailed meaning of them can be
found: https://lore.kernel.org/qemu-devel/31d6dbc1-f453-4cef-ab08-4813f4e0ff92@xxxxxxxxx/
Allow user to specify those values via property mrconfigid, mrowner and
mrownerconfig. They are all in base64 format.
example
-object tdx-guest, \
mrconfigid=ASNFZ4mrze8BI0VniavN7wEjRWeJq83vASNFZ4mrze8BI0VniavN7wEjRWeJq83v,\
mrowner=ASNFZ4mrze8BI0VniavN7wEjRWeJq83vASNFZ4mrze8BI0VniavN7wEjRWeJq83v,\
mrownerconfig=ASNFZ4mrze8BI0VniavN7wEjRWeJq83vASNFZ4mrze8BI0VniavN7wEjRWeJq83v
Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
Co-developed-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
[...]
diff --git a/qapi/qom.json b/qapi/qom.json
index 89ed89b9b46e..cac875349a3a 100644
--- a/qapi/qom.json
+++ b/qapi/qom.json
@@ -905,10 +905,25 @@
# pages. Some guest OS (e.g., Linux TD guest) may require this to
# be set, otherwise they refuse to boot.
#
+# @mrconfigid: ID for non-owner-defined configuration of the guest TD,
+# e.g., run-time or OS configuration (base64 encoded SHA384 digest).
+# (A default value 0 of SHA384 is used when absent).
Suggest to drop the parenthesis in the last sentence.
@mrconfigid is a string, so the default value can't be 0. Actually,
it's not just any string, but a base64 encoded SHA384 digest, which
means it must be exactly 96 hex digits. So it can't be "0", either. It
could be
"000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000".
I thought value 0 of SHA384 just means it.
That's my fault and my poor english.
"Fault" is too harsh :) It's not as precise as I want our interface
documentation to be. We work together to get there.
More on this below.
+#
+# @mrowner: ID for the guest TD’s owner (base64 encoded SHA384 digest).
+# (A default value 0 of SHA384 is used when absent).
+#
+# @mrownerconfig: ID for owner-defined configuration of the guest TD,
+# e.g., specific to the workload rather than the run-time or OS
+# (base64 encoded SHA384 digest). (A default value 0 of SHA384 is
+# used when absent).
+#
# Since: 9.0
##
{ 'struct': 'TdxGuestProperties',
- 'data': { '*sept-ve-disable': 'bool' } }
+ 'data': { '*sept-ve-disable': 'bool',
+ '*mrconfigid': 'str',
+ '*mrowner': 'str',
+ '*mrownerconfig': 'str' } }
##
# @ThreadContextProperties:
diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
index d0ad4f57b5d0..4ce2f1d082ce 100644
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -13,6 +13,7 @@
#include "qemu/osdep.h"
#include "qemu/error-report.h"
+#include "qemu/base64.h"
#include "qapi/error.h"
#include "qom/object_interfaces.h"
#include "standard-headers/asm-x86/kvm_para.h"
@@ -516,6 +517,7 @@ int tdx_pre_create_vcpu(CPUState *cpu, Error **errp)
X86CPU *x86cpu = X86_CPU(cpu);
CPUX86State *env = &x86cpu->env;
g_autofree struct kvm_tdx_init_vm *init_vm = NULL;
+ size_t data_len;
int r = 0;
object_property_set_bool(OBJECT(cpu), "pmu", false, &error_abort);
@@ -528,6 +530,38 @@ int tdx_pre_create_vcpu(CPUState *cpu, Error **errp)
init_vm = g_malloc0(sizeof(struct kvm_tdx_init_vm) +
sizeof(struct kvm_cpuid_entry2) * KVM_MAX_CPUID_ENTRIES);
+#define SHA384_DIGEST_SIZE 48
+
+ if (tdx_guest->mrconfigid) {
+ g_autofree uint8_t *data = qbase64_decode(tdx_guest->mrconfigid,
+ strlen(tdx_guest->mrconfigid), &data_len, errp);
+ if (!data || data_len != SHA384_DIGEST_SIZE) {
+ error_setg(errp, "TDX: failed to decode mrconfigid");
+ return -1;
+ }
+ memcpy(init_vm->mrconfigid, data, data_len);
+ }
When @mrconfigid is absent, the property remains null, and this
conditional is not executed. init_vm->mrconfigid[], an array of 6
__u64, remains all zero. How does the kernel treat that?
A all-zero SHA384 value is still a valid value, isn't it?
KVM treats it with no difference.
Can you point me to the spot in the kernel where mrconfigid is used?
https://github.com/intel/tdx/blob/66a10e258636fa8ec9f5ce687607bf2196a92341/arch/x86/kvm/vmx/tdx.c#L2322
KVM just copy what QEMU provides into its own data structure @td_params.
The format @of td_params is defined by TDX spec, and @td_params needs to
be passed to TDX module when initialize the context of TD via
SEAMCALL(TDH.MNG.INIT):
https://github.com/intel/tdx/blob/66a10e258636fa8ec9f5ce687607bf2196a92341/arch/x86/kvm/vmx/tdx.c#L2450
In fact, all the three SHA384 fields, will be hashed together with some
other fields (in td_params and other content of TD) to compromise the
initial measurement of TD.
TDX module doesn't care the value of td_params->mrconfigid.
