On 5/23/2022 5:39 PM, Gerd Hoffmann wrote:
Validate TD attributes with tdx_caps that fixed-0 bits must be zero and
fixed-1 bits must be set.
-static void setup_td_guest_attributes(X86CPU *x86cpu)
+static int tdx_validate_attributes(TdxGuest *tdx)
+{
+ if (((tdx->attributes & tdx_caps->attrs_fixed0) | tdx_caps->attrs_fixed1) !=
+ tdx->attributes) {
+ error_report("Invalid attributes 0x%lx for TDX VM (fixed0 0x%llx, fixed1 0x%llx)",
+ tdx->attributes, tdx_caps->attrs_fixed0, tdx_caps->attrs_fixed1);
+ return -EINVAL;
+ }
So, how is this supposed to work? Patch #2 introduces attributes as
user-settable property. So do users have to manually figure and pass
the correct value, so the check passes? Specifically the fixed1 check?
I think 'attributes' should not be user-settable in the first place.
Each feature-bit which is actually user-settable (and not already
covered by another option like pmu) should be a separate attribute for
tdx-object. Then the tdx code can create attributes from hardware
capabilities and user settings.
In patch #2, tdx-guest.attributes is defined as a field to hold a 64
bits value of attributes but it doesn't provide any getter/setter for
it. So it's *not* user-settable.
Did I miss something? (I'm not good at QEMU object)
When user-settable options might not be available depending on hardware
capabilities best practice is to create them as OnOffAuto properties.
Auto == qemu can pick the value, typical behavior is to enable the
feature if the hardware supports it.
On == must enable, if it isn't possible throw an error and exit.
Off == must disable, if it isn't possible throw an error and exit.
take care,
Gerd
