Re: [Qemu-devel] [PATCH RFC 0/3] s390x/tcg: LAP support using immediate TLB invalidation

[Cornelia Huck]

On Wed, 27 Sep 2017 19:00:24 +0200
David Hildenbrand <address@hidden> wrote:

> Details about Low-Address Protection can be found in description of
> patch 1 and 2. It is basically a subpage protection of the first two
> pages of every address space (for which it is enabled).
> 
> We can achieve this by simply directly invalidating the TLB entry and
> therefore forcing every write accesses onto these two pages into the slow
> path.
> 
> With this patch, I can boot Linux just fine (which uses LAP). This also
> makes all related kvm-unit-tests that we have pass.
> 
> The checks are working that good, that I discovered a STFL bug. STFL
> stores into the low addresses but low-address protection does explicitly
> not apply. The Linux kernel calls STFL while LAP is active. So without
> patch nr 3, booting Linux will fail. (this change is also part of a patch
> of my SMP series).

I fear I have lost track a bit with all those patches floating around.
IIUC, patch 3 fixes a real bug that is only exposed by your LAP
changes. It used to be part of the stfl changes in v1 of your smp
series but is no longer in v2. So, is this a patch that can be applied
to current s390-next?

> 
> Based on: https://github.com/cohuck/qemu.git s390-next
> Available on: https://github.com/dhildenb/qemu.git s390x_lap
> 
> 
> David Hildenbrand (3):
>   accel/tcg: allow to invalidate a write TLB entry immediately
>   s390x/tcg: low-address protection support
>   s390x/tcg: make STFL store into the lowcore
> 
>  accel/tcg/cputlb.c           |  5 ++-
>  accel/tcg/softmmu_template.h |  4 +-
>  include/exec/cpu-all.h       |  3 ++
>  target/s390x/excp_helper.c   |  3 +-
>  target/s390x/helper.h        |  2 +-
>  target/s390x/mem_helper.c    |  8 ----
>  target/s390x/misc_helper.c   |  7 +++-
>  target/s390x/mmu_helper.c    | 96 
> ++++++++++++++++++++++++++++----------------
>  8 files changed, 78 insertions(+), 50 deletions(-)
>