Subject: Re: [PATCH v2] KVM: PPC: Book3S HV: use smp_mb() when setting/clearing host_ipi flag

From: Michael Ellerman <[email-masked]>
Date: Wed, 25 Sep 2019 21:05:20 +1000 (AEST)

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 <[email-masked]>
> Cc: Paul Mackerras <[email-masked]>
> Cc: Nicholas Piggin <[email-masked]>
> Cc: [email-masked]
> Signed-off-by: Michael Roth <[email-masked]>

Applied to powerpc fixes, thanks.

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

cheers