linux-kernel - Re: [PATCH v2 1/2] KVM: s390: pv: simplify shutdown and fix race

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Date:   Tue, 11 Jul 2023 17:18:28 +0200
From:   Nico Boehr <nrb@...ux.ibm.com>
To:     Claudio Imbrenda <imbrenda@...ux.ibm.com>, kvm@...r.kernel.org
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        frankja@...ux.ibm.com, mhartmay@...ux.ibm.com, nsg@...ux.ibm.com,
        borntraeger@...ibm.com
Subject: Re: [PATCH v2 1/2] KVM: s390: pv: simplify shutdown and fix race

Quoting Claudio Imbrenda (2023-07-05 13:19:36)
> Simplify the shutdown of non-protected VMs. There is no need to do
> complex manipulations of the counter if it was zero.
> 
> This also fixes a very rare race which caused pages to be torn down
> from the address space with a non-zero counter even on older machines
> that don't support the UVC instruction, causing a crash.
> 
> Reported-by: Marc Hartmayer <mhartmay@...ux.ibm.com>
> Fixes: fb491d5500a7 ("KVM: s390: pv: asynchronous destroy for reboot")
> Signed-off-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>

Reviewed-by: Nico Boehr <nrb@...ux.ibm.com>