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Date:   Thu, 27 Jul 2023 17:07:24 +0200
From:   Claudio Imbrenda <imbrenda@linux.ibm.com>
To:     Steffen Eiden <seiden@linux.ibm.com>
Cc:     linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org,
        kvm@vger.kernel.org, Janosch Frank <frankja@linux.ibm.com>,
        David Hildenbrand <david@redhat.com>,
        Michael Mueller <mimu@linux.vnet.ibm.com>,
        Marc Hartmayer <mhartmay@linux.ibm.com>
Subject: Re: [PATCH 3/3] KVM: s390: pv:  Allow AP-instructions for pv guests
Message-ID: <20230727170724.7adb71fa@p-imbrenda>
In-Reply-To: <20230727122053.774473-4-seiden@linux.ibm.com>
References: <20230727122053.774473-1-seiden@linux.ibm.com>
        <20230727122053.774473-4-seiden@linux.ibm.com>
Organization: IBM
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On Thu, 27 Jul 2023 14:20:53 +0200
Steffen Eiden <seiden@linux.ibm.com> wrote:

> Introduces new feature bits and enablement flags for AP and AP IRQ
> support.
> 
> Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
> ---
>  arch/s390/include/asm/uv.h | 12 +++++++++++-
>  arch/s390/kvm/pv.c         |  8 ++++++--
>  2 files changed, 17 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
> index 338845402324..913ccfaa9d76 100644
> --- a/arch/s390/include/asm/uv.h
> +++ b/arch/s390/include/asm/uv.h
> @@ -99,6 +99,8 @@ enum uv_cmds_inst {
>  enum uv_feat_ind {
>  	BIT_UV_FEAT_MISC = 0,
>  	BIT_UV_FEAT_AIV = 1,
> +	BIT_UV_FEAT_AP = 4,
> +	BIT_UV_FEAT_AP_INTR = 5,
>  };
>  
>  struct uv_cb_header {
> @@ -159,7 +161,15 @@ struct uv_cb_cgc {
>  	u64 guest_handle;
>  	u64 conf_base_stor_origin;
>  	u64 conf_virt_stor_origin;
> -	u64 reserved30;
> +	u8  reserved30[6];
> +	union {
> +		struct {
> +			u16 reserved : 14;
> +			u16 ap_instr_intr : 1;
> +			u16 ap_allow_instr : 1;
> +		};
> +		u16 raw;
> +	} flags;
>  	u64 guest_stor_origin;
>  	u64 guest_stor_len;
>  	u64 guest_sca;
> diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
> index 899f3b8ac011..103add1894c9 100644
> --- a/arch/s390/kvm/pv.c
> +++ b/arch/s390/kvm/pv.c
> @@ -561,12 +561,16 @@ int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
>  	uvcb.conf_base_stor_origin =
>  		virt_to_phys((void *)kvm->arch.pv.stor_base);
>  	uvcb.conf_virt_stor_origin = (u64)kvm->arch.pv.stor_var;
> +	uvcb.flags.ap_allow_instr = uv_has_feature(BIT_UV_FEAT_AP) &&
> +				    kvm->arch.model.uv_feat_guest.ap;

how can it happen that uv_feat_guest.ap is set but
uv_has_feature(BIT_UV_FEAT_AP) is 0 ?

in the previous patch you check for the feature before allowing the bit
to be set.

> +	uvcb.flags.ap_instr_intr = uv_has_feature(BIT_UV_FEAT_AP_INTR) &&
> +				   kvm->arch.model.uv_feat_guest.ap_intr;

same here

>  
>  	cc = uv_call_sched(0, (u64)&uvcb);
>  	*rc = uvcb.header.rc;
>  	*rrc = uvcb.header.rrc;
> -	KVM_UV_EVENT(kvm, 3, "PROTVIRT CREATE VM: handle %llx len %llx rc %x rrc %x",
> -		     uvcb.guest_handle, uvcb.guest_stor_len, *rc, *rrc);
> +	KVM_UV_EVENT(kvm, 3, "PROTVIRT CREATE VM: handle %llx len %llx rc %x rrc %x flags %04x",
> +		     uvcb.guest_handle, uvcb.guest_stor_len, *rc, *rrc, uvcb.flags.raw);
>  
>  	/* Outputs */
>  	kvm->arch.pv.handle = uvcb.guest_handle;