Message-ID: <af066c18-6e75-d260-274f-87ae1b29f9d2@linux.ibm.com>
Date:   Thu, 13 Jan 2022 11:30:13 +0100
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Subject: Re: [PATCH v6 09/17] KVM: s390: pv: clear the state without memset
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To:     Claudio Imbrenda <imbrenda@linux.ibm.com>, kvm@vger.kernel.org
Cc:     cohuck@redhat.com, borntraeger@de.ibm.com, thuth@redhat.com,
        pasic@linux.ibm.com, david@redhat.com, linux-s390@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20211203165814.73016-1-imbrenda@linux.ibm.com>
 <20211203165814.73016-10-imbrenda@linux.ibm.com>
From:   Janosch Frank <frankja@linux.ibm.com>
In-Reply-To: <20211203165814.73016-10-imbrenda@linux.ibm.com>
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Precedence: bulk

On 12/3/21 17:58, Claudio Imbrenda wrote:
> Do not use memset to clean the whole struct kvm_s390_pv; instead,
> explicitly clear the fields that need to be cleared.
> 
> Upcoming patches will introduce new fields in the struct kvm_s390_pv
> that will not need to be cleared.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> ---
>   arch/s390/kvm/pv.c | 11 ++++++++++-
>   1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
> index 04aa4a20260b..59da54bd6b21 100644
> --- a/arch/s390/kvm/pv.c
> +++ b/arch/s390/kvm/pv.c
> @@ -16,6 +16,15 @@
>   #include <linux/sched/mm.h>
>   #include "kvm-s390.h"
>   
> +static void kvm_s390_clear_pv_state(struct kvm *kvm)
> +{
> +	kvm->arch.pv.handle = 0;
> +	kvm->arch.pv.guest_len = 0;
> +	kvm->arch.pv.stor_base = 0;
> +	kvm->arch.pv.stor_var = NULL;
> +	kvm->arch.pv.handle = 0;

We could use the same approach that we use in qemu to do the cpu resets.
But maybe that would be overkill for a few struct members.

> +}
> +
>   int kvm_s390_pv_destroy_cpu(struct kvm_vcpu *vcpu, u16 *rc, u16 *rrc)
>   {
>   	int cc;
> @@ -110,7 +119,7 @@ static void kvm_s390_pv_dealloc_vm(struct kvm *kvm)
>   	vfree(kvm->arch.pv.stor_var);
>   	free_pages(kvm->arch.pv.stor_base,
>   		   get_order(uv_info.guest_base_stor_len));
> -	memset(&kvm->arch.pv, 0, sizeof(kvm->arch.pv));
> +	kvm_s390_clear_pv_state(kvm);
>   }
>   
>   static int kvm_s390_pv_alloc_vm(struct kvm *kvm)
>