linux-kernel - Re: [PATCH v11 13/19] KVM: s390: pv: destroy the configuration before its memory

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Date:   Tue, 14 Jun 2022 16:23:14 +0200
From:   Janosch Frank <frankja@...ux.ibm.com>
To:     Claudio Imbrenda <imbrenda@...ux.ibm.com>, kvm@...r.kernel.org
Cc:     borntraeger@...ibm.com, thuth@...hat.com, pasic@...ux.ibm.com,
        david@...hat.com, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, scgl@...ux.ibm.com,
        mimu@...ux.ibm.com, nrb@...ux.ibm.com
Subject: Re: [PATCH v11 13/19] KVM: s390: pv: destroy the configuration before
 its memory

On 6/3/22 08:56, Claudio Imbrenda wrote:
> Move the Destroy Secure Configuration UVC before the loop to destroy
> the memory. If the protected VM has memory, it will be cleaned up and
> made accessible by the Destroy Secure Configuraion UVC. The struct

s/Configuraion/Configuration/

> page for the relevant pages will still have the protected bit set, so
> the loop is still needed to clean that up.
> 
> Switching the order of those two operations does not change the
> outcome, but it is significantly faster.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>

Reviewed-by: Janosch Frank <frankja@...ux.ibm.com>

> ---
>   arch/s390/kvm/pv.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
> index a389555d62e7..6cffea26c47f 100644
> --- a/arch/s390/kvm/pv.c
> +++ b/arch/s390/kvm/pv.c
> @@ -163,6 +163,9 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
>   {
>   	int cc;
>   
> +	cc = uv_cmd_nodata(kvm_s390_pv_get_handle(kvm),
> +			   UVC_CMD_DESTROY_SEC_CONF, rc, rrc);
> +	WRITE_ONCE(kvm->arch.gmap->guest_handle, 0);
>   	/*
>   	 * if the mm still has a mapping, make all its pages accessible
>   	 * before destroying the guest
> @@ -172,9 +175,6 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
>   		mmput(kvm->mm);
>   	}
>   
> -	cc = uv_cmd_nodata(kvm_s390_pv_get_handle(kvm),
> -			   UVC_CMD_DESTROY_SEC_CONF, rc, rrc);
> -	WRITE_ONCE(kvm->arch.gmap->guest_handle, 0);
>   	if (!cc) {
>   		atomic_dec(&kvm->mm->context.protected_count);
>   		kvm_s390_pv_dealloc_vm(kvm);