Re: [PATCH v8 2/7] kexec: define functions to map and unmap segments

[steven chen]

On 2/24/2025 4:18 PM, Baoquan He wrote:
> On 02/24/25 at 03:05pm, steven chen wrote:
> > On 2/23/2025 10:14 PM, Baoquan He wrote:
> > > Hi Steve, Mimi,
> > >
> > > On 02/18/25 at 02:54pm, steven chen wrote:
> > > > Currently, the mechanism to map and unmap segments to the kimage
> > > > structure is not available to the subsystems outside of kexec.  This
> > > > functionality is needed when IMA is allocating the memory segments
> > > > during kexec 'load' operation.  Implement functions to map and unmap
> > > > segments to kimage.
> > > I am done with the whole patchset understanding. My concern is if this
> > > TPM PCRs content can be carried over through newly introduced KHO. I can
> > > see that these patchset doesn't introduce too much new code changes,
> > > while if many conponents need do this, kexec reboot will be patched all
> > > over its body and become ugly and hard to maintain.
> > >
> > > Please check Mike Rapoport's v4 patchset to see if IMA can register
> > > itself to KHO and do somthing during 2nd kernel init to restore those
> > > TPM PCRs content to make sure all measurement logs are read correctly.
> > > [PATCH v4 00/14] kexec: introduce Kexec HandOver (KHO)
> > >
> > > Thanks
> > > Baoquan
> > Hi Baoquan,
> >
> > For IMA, it appears that there are no current issues with TPM PCRs after a
> > kernel soft reboot.
> I mean using KHO to hold in 1st kernel and restore the IMA log in 2nd
> kernel.
>
> > This patches is used to get currently missed IMA measurements during the
> > kexec process copied to new kernel after the kernel soft reboot. I think
> > it's ok to leave it at current location: it will be easy to maintain for
> > IMA.
> Yeah, but I am saying this patchset increase unnecessary code
> complexity in kexec code maintaining.
>
> > Overall, for these patches, do you see any major blockers for kexec?
> >
> > If you have any specific concerns or need further details, please let me
> > know.
> I have no concerns for this patchset implementation itself, I saw you using
> vmap to maping the possible scattered source pages smartly and taking
> the mapped buffer pointers to update later duing kexec jumping. That's very
> great and clever method. BUT I am concerned about the solution, if we
> can make use of the existed way of KHO to implement it more simply. Could
> you please do investigation?

Hi Baoquan,

I will conduct an investigation. Thank you for your comments.

Steven