Re: [kvm-unit-tests GIT PULL 07/26] s390x: sie: ensure guests are aligned to 2GB

Nina Schoetterl-Glausch
2023-11-23T09:24:48Z

On Wed, 2023-11-22 at 12:06 +0100, Thomas Huth wrote:
> On 10/11/2023 14.52, Nico Boehr wrote:
> > Until now, kvm-unit-tests has aligned guests to 1 MB in the host virtual
> > address space. Unfortunately, some s390x environments require guests to
> > be 2GB aligned in the host virtual address space, preventing
> > kvm-unit-tests which act as a hypervisor from running there.
> >
> > We can't easily put guests at address 0, since we want to be able to run
> > with MSO/MSL without having to maintain separate page tables for the
> > guest physical memory. 2GB is also not a good choice, since the
> > alloc_pages allocator will place its metadata there when the host has
> > more than 2GB of memory. In addition, we also want a bit of space after
> > the end of the host physical memory to be able to catch accesses beyond
> > the end of physical memory.
> >
> > The vmalloc allocator unfortunately allocates memory starting at the
> > highest virtual address which is not suitable for guest memory either
> > due to additional constraints of some environments.
> >
> > The physical page allocator in memalign_pages() is also not a optimal
> > choice, since every test running SIE would then require at least 4GB+1MB
> > of physical memory.
> >
> > This results in a few quite complex allocation requirements, hence add a
> > new function sie_guest_alloc() which allocates memory for a guest and
> > then establishes a properly aligned virtual space mapping.
> >
> > Rework snippet test and sie tests to use the new sie_guest_alloc()
> > function.
> >
> > Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> > Link: https://lore.kernel.org/r/20231106170849.1184162-3-nrb@linux.ibm.com
> > Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
> > ---
> > lib/s390x/sie.h | 2 ++
> > lib/s390x/snippet.h | 9 +++------
> > lib/s390x/sie.c | 42 ++++++++++++++++++++++++++++++++++++++++++
> > s390x/sie.c | 4 ++--
> > 4 files changed, 49 insertions(+), 8 deletions(-)
>
> Hi Nico!
>
> a colleague of mine (Jan) told me today that the current SIE-related tests
> of the kvm-unit-tests are failing when being run from a KVM guest (i.e. when
> we're testing a double-nested scenario). I've bisected the problem and ended
> up with this patch here.
> Could you please check whether "./run_tests.sh sie mvpg-sie spec_ex-sie"
> still works for you from within a KVM guest?

If you're getting a validity intercept, this should be fixed by
KVM: s390: vsie: fix wrong VIR 37 when MSO is used
https://lore.kernel.org/kvm/20231102153549.53984-1-imbrenda@linux.ibm.com/
>
> Thanks,
> Thomas
>
>