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

[Huang, Kai]

On Fri, 2024-09-06 at 16:36 -0700, Dan Williams wrote:
> How about:
> 
>     Subject: x86/virt/tdx: Require the module to assert it has the NO_RBP_MOD mitigation
> 
> ...to avoid the double negative.

Will do.  Thanks.

> 
> 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:

Will do.  If I got it right, the link with message-id should be:

https://lore.kernel.org/all/fc0e8ab7-86d4-4428-be31-82e1ece6dd21@xxxxxxxxx/

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

Thanks.