Re: [PATCH 0/3] Resolve problems with kexec identity mapping

[Steve Wahl]

On Tue, Jul 09, 2024 at 12:37:42PM +0200, Borislav Petkov wrote:
> On Tue, Jul 09, 2024 at 08:49:43AM +0200, Ard Biesheuvel wrote:
> > > Patch #2 adds the CC blob to the identity map as well, if present,
> > > since if present it is also dereferenced before the page fault handler
> > > can be put into place.  Given what's been discussed, this patch might
> > > not be necessary; I don't know enough to say whether kexec-ing a new
> > > kernel within a SEV guest makes sense.  I'm pretty certain it can
> > > cause no harm, though.
> 
> No, keep it in the bag until it is really needed. No proactive "fixing".
> 
> > I'd prefer it if that is addressed within the context of the SEV guest
> > work. The memory setup is quite intricate, and dealing with individual
> > types of EFI config tables is something we should avoid in general. I
> > still maintain that the best approach would be to map all of DRAM 1:1
> > instead of mapping patches left and right (as this is what EFI does),
> > but if we need to do so, let's keep it as generic as we possibly can.
> 
> Sure. There's the kink that coco guests need to accept memory first and
> mapping it all is the least performant one. But we can deal with that later.
> 
> > I wasn't cc'ed on any of the patches so I don't know exactly what was
> > discussed.
> > 
> > Please cc me and linux-efi@ on your next revision.
> 
> And please update your commit messages with what was discussed on this thread.
> 
> Thx.

Thanks, Boris.  I'll give it my best shot.

Next version will leave out the current patch #2, and update the
comments to include this conversation somehow summarized.

I think perhaps the cover letter was also too verbose on the history
and unintentionally hid the information necesary to understand the
situation.  I will try to make it more concise.

--> Steve


-- 
Steve Wahl, Hewlett Packard Enterprise