Re: [PATCH 2/2] examples: systemtap: Update to linux-6.3

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On Mon, Mar 06, 2023 at 12:26:24PM +0100, Peter Krempa wrote:
> On Mon, Mar 06, 2023 at 10:37:54 +0000, Daniel P. Berrangé wrote:
> > On Mon, Mar 06, 2023 at 11:21:54AM +0100, Peter Krempa wrote:
> > > The 'vmsa' struct was moved out of 'struct vcpu_svm' in linux commit:
> > > 
> > >   commit b67a4cc35c9f726999fa29880713ce72d4e39e8d
> > >   Author: Peter Gonda <pgonda@xxxxxxxxxx>
> > >   Date:   Thu Oct 21 10:42:59 2021 -0700
> > > 
> > >       KVM: SEV: Refactor out sev_es_state struct
> > > 
> > >       Move SEV-ES vCPU metadata into new sev_es_state struct from vcpu_svm.
> > > 
> > > Also update the line reference for linux-6.3.
> > > 
> > > NB: I strongly considered removing the example as it's impossible to
> > > keep in sync. With the warning added by previous commit I think we can
> > > give it one more chance.
> > 
> > It sucks, but it sucks less than what every was doing before I
> > suggested systemtap, which is to tell people to edit their
> > kernel source to add printfs and then rebuild their kernel
> > 
> > Ideally the kernel would expose the pristine expected VMSA
> > data in some sane interface like debugfs.
> > 
> > > 
> > > Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2175598
> > 
> > In general such bugs should be closed WONTFIX. There is no
> > expectation that this demo works on RHEL kernels. At most I
> > would worry about upstream kernel, but even that's not very
> > critical. This is just a demo of the approach you should take
> > not a supported script we expect to work out of the box.
> 
> I agree. I'll close this one.
> 
> > 
> > > Signed-off-by: Peter Krempa <pkrempa@xxxxxxxxxx>
> > > ---
> > >  examples/systemtap/amd-sev-es-vmsa.stp | 6 +++---
> > >  1 file changed, 3 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/examples/systemtap/amd-sev-es-vmsa.stp b/examples/systemtap/amd-sev-es-vmsa.stp
> > > index 14bfb01c10..ab2f202681 100644
> > > --- a/examples/systemtap/amd-sev-es-vmsa.stp
> > > +++ b/examples/systemtap/amd-sev-es-vmsa.stp
> > > @@ -46,7 +46,7 @@ function dump_vmsa(addr:long) {
> > >  # is the one beween the call to clflush_cache_range(...) and the
> > >  # call to sev_issue_cmd(kvm, SEV_CMD_LAUNCH_UPDATE...).
> > >  #
> > > -# Line 632 is correct for Linux v6.0
> > > -probe module("kvm_amd").statement("__sev_launch_update_vmsa@arch/x86/kvm/svm/sev.c:632") {
> > > -  dump_vmsa($svm->vmsa)
> > > +# Line 635 is correct for Linux v6.3
> > > +probe module("kvm_amd").statement("__sev_launch_update_vmsa@arch/x86/kvm/svm/sev.c:635") {
> > > +  dump_vmsa($svm->sev_es->vmsa)
> 
> At least the change to this line IMO makes sense from upstream's POV
> going forward as the code was refactored and thus the old example will
> never work again with new kernels.

Yes, I'm fine with changes to this demo program if they're presented
simply as following LKML latest git impl.

With regards,
Daniel
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