linux-kernel - Re: [PATCH 16/32] KVM: s390: expose the guest zPCI interpretation facility

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Date:   Fri, 17 Dec 2021 16:05:34 +0100
From:   Christian Borntraeger <borntraeger@...ux.ibm.com>
To:     Matthew Rosato <mjrosato@...ux.ibm.com>, linux-s390@...r.kernel.org
Cc:     alex.williamson@...hat.com, cohuck@...hat.com,
        schnelle@...ux.ibm.com, farman@...ux.ibm.com, pmorel@...ux.ibm.com,
        hca@...ux.ibm.com, gor@...ux.ibm.com,
        gerald.schaefer@...ux.ibm.com, agordeev@...ux.ibm.com,
        frankja@...ux.ibm.com, david@...hat.com, imbrenda@...ux.ibm.com,
        vneethv@...ux.ibm.com, oberpar@...ux.ibm.com, freude@...ux.ibm.com,
        thuth@...hat.com, pasic@...ux.ibm.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 16/32] KVM: s390: expose the guest zPCI interpretation
 facility



Am 07.12.21 um 21:57 schrieb Matthew Rosato:
> This facility will be used to enable interpretive execution of zPCI
> instructions.
> 
> Signed-off-by: Matthew Rosato <mjrosato@...ux.ibm.com>
> ---
>   arch/s390/kvm/kvm-s390.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index c8fe9b7c2395..09991d05c871 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -2751,6 +2751,10 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
>   		set_kvm_facility(kvm->arch.model.fac_mask, 147);
>   		set_kvm_facility(kvm->arch.model.fac_list, 147);
>   	}
> +	if (sclp.has_zpci_interp && test_facility(69)) {
> +		set_kvm_facility(kvm->arch.model.fac_mask, 69);
> +		set_kvm_facility(kvm->arch.model.fac_list, 69);
> +	}


Do we need the setting of these stfle bits somewhere? I think QEMU sets them as well for the guest.
We only need this when the kernel probes for this (test_kvm_facility) But then the question is, shouldnt
we then simply check for sclp bits in those places?
See also patch 19. We need to build it in a way that allows VSIE support later on.

>   
>   	if (css_general_characteristics.aiv && test_facility(65))
>   		set_kvm_facility(kvm->arch.model.fac_mask, 65);
>