linux-kernel - Re: [PATCH v1 1/1] KVM: s390/mm: Properly reset no-dat

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Message-ID: <20231109134428.613ba70e@p-imbrenda>
Date:   Thu, 9 Nov 2023 13:44:28 +0100
From:   Claudio Imbrenda <imbrenda@...ux.ibm.com>
To:     kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        frankja@...ux.ibm.com, nrb@...ux.ibm.com, nsg@...ux.ibm.com,
        borntraeger@...ibm.com, hca@...ux.ibm.com,
        gerald.schaefer@...ux.ibm.com, gor@...ux.ibm.com,
        svens@...ux.ibm.com, agordeev@...ux.ibm.com
Subject: Re: [PATCH v1 1/1] KVM: s390/mm: Properly reset no-dat

Sorry, I had copy-pasted the wrong email address for Gerald, fixed now

On Thu,  9 Nov 2023 13:36:24 +0100
Claudio Imbrenda <imbrenda@...ux.ibm.com> wrote:

> When the CMMA state needs to be reset, the no-dat bit also needs to be
> reset. Failure to do so could cause issues in the guest, since the
> guest expects the bit to be cleared after a reset.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
> ---
>  arch/s390/mm/pgtable.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
> index 3bd2ab2a9a34..5cb92941540b 100644
> --- a/arch/s390/mm/pgtable.c
> +++ b/arch/s390/mm/pgtable.c
> @@ -756,7 +756,7 @@ void ptep_zap_unused(struct mm_struct *mm, unsigned long addr,
>  		pte_clear(mm, addr, ptep);
>  	}
>  	if (reset)
> -		pgste_val(pgste) &= ~_PGSTE_GPS_USAGE_MASK;
> +		pgste_val(pgste) &= ~(_PGSTE_GPS_USAGE_MASK | _PGSTE_GPS_NODAT);
>  	pgste_set_unlock(ptep, pgste);
>  	preempt_enable();
>  }