Re: [PATCH v3 04/21] x86/virt/tdx: Add skeleton for detecting and initializing TDX on demand

[Sathyanarayanan Kuppuswamy]

On 4/19/22 9:37 PM, Kai Huang wrote:
> On Tue, 2022-04-19 at 07:53 -0700, Sathyanarayanan Kuppuswamy wrote:
> > On 4/5/22 9:49 PM, Kai Huang wrote:
> > > The TDX module is essentially a CPU-attested software module running
> > > in the new Secure Arbitration Mode (SEAM) to protect VMs from malicious
> > > host and certain physical attacks.  The TDX module implements the
> >
> > /s/host/hosts
>
> I don't quite get.  Could you explain why there are multiple hosts?

Sorry, I misread it. It is correct, so ignore it.

> >

> > > +
> > > +/**
> > > + * tdx_detect - Detect whether the TDX module has been loaded
> > > + *
> > > + * Detect whether the TDX module has been loaded and ready for
> > > + * initialization.  Only call this function when all cpus are
> > > + * already in VMX operation.
> > > + *
> > > + * This function can be called in parallel by multiple callers.
> > > + *
> > > + * Return:
> > > + *
> > > + * * -0:	The TDX module has been loaded and ready for
> > > + *		initialization.
> > > + * * -ENODEV:	The TDX module is not loaded.
> > > + * * -EPERM:	CPU is not in VMX operation.
> > > + * * -EFAULT:	Other internal fatal errors.
> > > + */
> > > +int tdx_detect(void)
> >
> > Will this function be used separately or always along with
> > tdx_init()?
>
> The caller should first use tdx_detect() and then use tdx_init().  If caller
> only uses tdx_detect(), then TDX module won't be initialized (unless other
> caller does this).  If caller calls tdx_init() before tdx_detect(),  it will get
> error.

I just checked your patch set to understand where you are using
tdx_detect()/tdx_init(). But I did not find any callers. Did I miss it? 
or it is not used in your patch set?

--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer