Re: [PATCH 3/4] x86/kexec(): Reset TDX private memory on platforms with TDX erratum

[Huang, Kai]

On 1/02/2024 10:39 pm, Kirill A. Shutemov wrote:
> On Thu, Feb 01, 2024 at 10:22:18PM +0800, Huang, Kai wrote:
> > On 1/02/2024 6:03 am, Kirill A. Shutemov wrote:
> > > On Wed, Jan 31, 2024 at 01:21:39PM -0800, Dave Hansen wrote:
> > > > >    #ifdef CONFIG_KEXEC_JUMP
> > > > >    	if (image->preserve_context)
> > > > >    		save_processor_state();
> > > > > +	else
> > > > > +		tdx_reset_memory();
> > > > > +#else
> > > > > +	tdx_reset_memory();
> > > > >    #endif
> > > >
> > > > Wow, that's awfully hard to read.  I really wish folks' gag reflex would
> > > > kick in when they see stuff like this to get them to spend an additional
> > > > 15 seconds to turn this into:
> > > >
> > > > 	if (IS_ENABLED(CONFIG_KEXEC_JUMP) && image->preserve_context)
> > > > 		save_processor_state();
> > > > 	else
> > > > 		tdx_reset_memory();
> > >
> > > save_processor_state() is declared under CONFIG_PM_SLEEP, so I guess your
> > > variant might break build in some cases without updated suspend.h.
> >
> > I tried.  If I turn off both SUSPEND and HIBERNATION in the Kconfig I got
> > build error：
> >
> > arch/x86/kernel/machine_kexec_64.c:325:17: error: implicit declaration of
> > function ‘save_processor_state’ [-Werror=implicit-function-declaration]
> >    325 |                 save_processor_state();
> >        |                 ^~~~~~~~~~~~~~~~~~~~
>
> Moving save_processor_state() declaration outside all defines would do the
> trick.
>
> Something like the patch below.
>
> But finding the right spot for the move can be tricky. I don't particular
> like where I moved it.

I don't feel I have enough justification to do such change.

As I replied in another email, how about:

#ifdef CONFIG_KEXEC_JUMP
    if (image->preserve_context)
        save_processor_state();
    else
#endif
    tdx_reset_memory();

Not ideal, but looks slightly better?

But I'll leave to Dave to comment.