Re: [PATCH v3 8/8] x86/virt/tdx: Don't initialize module that doesn't support NO_RBP_MOD feature

[Dan Williams]

How about:

    Subject: x86/virt/tdx: Require the module to assert it has the NO_RBP_MOD mitigation

...to avoid the double negative.

Kai Huang wrote:
> Old TDX modules can clobber RBP in the TDH.VP.ENTER SEAMCALL.  However
> RBP is used as frame pointer in the x86_64 calling convention, and
> clobbering RBP could result in bad things like being unable to unwind
> the stack if any non-maskable exceptions (NMI, #MC etc) happens in that
> gap.
> 
> A new "NO_RBP_MOD" feature was introduced to more recent TDX modules to
> not clobber RBP.  This feature is reported in the TDX_FEATURES0 global
> metadata field via bit 18.
> 
> Don't initialize the TDX module if this feature is not supported [1].
> 
> Link: https://lore.kernel.org/all/c0067319-2653-4cbd-8fee-1ccf21b1e646@xxxxxxxx/T/#mef98469c51e2382ead2c537ea189752360bd2bef [1]

Trim this to the direct message-id format, but otherwise:

Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>