linux-kernel - Re: [PATCH RFC 2/2] KVM: s390: introduce and use KVM_REQ_VSIE

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Date:   Tue, 7 Aug 2018 19:06:26 +0200
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org
Cc:     linux-s390@...r.kernel.org,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>
Subject: Re: [PATCH RFC 2/2] KVM: s390: introduce and use KVM_REQ_VSIE_RESTART

On 07/08/2018 14:51, David Hildenbrand wrote:
> When we change the crycb (or execution controls), we also have to make sure
> that the vSIE shadow datastructures properly consider the changed
> values before rerunning the vSIE. We can achieve that by simply using a
> VCPU request now.
>
> This has to be a synchronous request (== handled before entering the
> (v)SIE again).
>
> The request will make sure that the vSIE handler is left, and that the
> request will be processed (NOP), therefore forcing a reload of all
> vSIE data (including rebuilding the crycb) when re-entering the vSIE
> interception handler the next time.
>
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>   arch/s390/include/asm/kvm_host.h | 1 +
>   arch/s390/kvm/kvm-s390.c         | 7 ++++++-
>   2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index 29c940bf8506..75d39628f21d 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -44,6 +44,7 @@
>   #define KVM_REQ_ICPT_OPEREXC	KVM_ARCH_REQ(2)
>   #define KVM_REQ_START_MIGRATION KVM_ARCH_REQ(3)
>   #define KVM_REQ_STOP_MIGRATION  KVM_ARCH_REQ(4)
> +#define KVM_REQ_VSIE_RESTART	KVM_ARCH_REQ(5)
>   
>   #define SIGP_CTRL_C		0x80
>   #define SIGP_CTRL_SCN_MASK	0x3f
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index c87734a31fdb..2fdc017d91f0 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -842,8 +842,11 @@ void kvm_s390_vcpu_crypto_reset_all(struct kvm *kvm)
>   
>   	kvm_s390_vcpu_block_all(kvm);
>   
> -	kvm_for_each_vcpu(i, vcpu, kvm)
> +	kvm_for_each_vcpu(i, vcpu, kvm) {
>   		kvm_s390_vcpu_crypto_setup(vcpu);
> +		/* recreate the shadow crycb by leaving the VSIE handler */
> +		kvm_s390_sync_request(KVM_REQ_VSIE_RESTART, vcpu);
> +	}
>   
>   	kvm_s390_vcpu_unblock_all(kvm);
>   }
> @@ -3201,6 +3204,8 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
>   
>   	/* nothing to do, just clear the request */
>   	kvm_clear_request(KVM_REQ_UNHALT, vcpu);
> +	/* we left the vsie handler, nothing to do, just clear the request */
> +	kvm_clear_request(KVM_REQ_VSIE_RESTART, vcpu);
>   
>   	return 0;
>   }

Reviewed-by: Pierre Morel<pmorel@...ux.ibm.com>
Tested-by: Pierre Morel<pmorel@...ux.ibm.com>


-- 
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany