Re: [Xen-devel] [Very RFC PATCH] Livepatch - initial ARM64/32 support.

[Konrad Rzeszutek Wilk <konrad@xxxxxxxxxx>]

On Thu, Aug 11, 2016 at 12:05:33PM -0700, Stefano Stabellini wrote:
> On Thu, 11 Aug 2016, Julien Grall wrote:
> > On 09/08/2016 06:18, Konrad Rzeszutek Wilk wrote:
> > > Hey!
> > 
> > Hi Konrad,
> > 
> > > Over the last couple of months in my spare time I was playing
> > > with making livepatch work with ARM64 (using the FoundationModel
> > > simulator) and I finally got it working tonight.
> > 
> > Congrats!
> 
> Indeed, congratulations! I hope it was fun :-)

Yes!
> 
> 
> > > Sending out the patches just in case they don't work tomorrow :-)
> > > 
> > > The ARM32 part is going slowly - as I don't have a simulator
> > > and using a real board takes time.
> > 
> > Whilst I can see usage of livepatch for Xen ARM64 (e.g server), I am less
> > convinced for ARM32. I am bit worry to check-in code that will get rotten in
> > the long term. So do you see any usage on ARM32?
> 
> Actually I think it is useful for embedded use cases too: think about
> security updates for any embedded devices which cannot easily be
> rebooted. Or even if they can be rebooted, it might create a
> competitive advantage to build a car that can be updated for critical
> security fixes without requesting the driver to stop.

My 'usage' is that ARM32 is the only board ARM board I've that
boots and runs without issues :-)

Either way the idea is that the test-cases will work on both
ARM32/ARM64/x86 - and I do plan to have them as part of OSSTest - so
I am not that afraid of the bitrotten part.

However for simplicity and review I will redo the patches without the
ARM32 part (the ELF part is the headache one) and keep on poking
at them until I get ARM32 working all the way (probably Xen 4.9 material).

And it was fun learning the opcodes, thought I still have much to learn.


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