On Wed, 2019-09-11 at 22:31:55 UTC, Michael Roth wrote:

On a 2-socket Power9 system with 32 cores/128 threads (SMT4) and 1TB
of memory running the following guest configs:

...

To handle both cases, this patch splits kvmppc_set_host_ipi() into
separate set/clear functions, where we execute smp_mb() prior to
setting host_ipi flag, and after clearing host_ipi flag. These
functions pair with each other to synchronize the sender and receiver
sides.

With that change in place the above workload ran for 20 hours without
triggering any lock-ups.

Fixes: 755563bc79c7 ("powerpc/powernv: Fixes for hypervisor doorbell handling") # v4.0
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <redacted>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: kvm-ppc@vger.kernel.org
Signed-off-by: Michael Roth <redacted>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/3a83f677a6eeff65751b29e3648d7c69c3be83f3

cheers