linux-kernel - Re: [PATCH v4 01/15] s390: zcrypt: externalize AP instructions available function

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Date:   Fri, 4 May 2018 09:19:45 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Tony Krowiak <akrowiak@...ux.vnet.ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     freude@...ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, borntraeger@...ibm.com,
        cohuck@...hat.com, kwankhede@...dia.com,
        bjsdjshi@...ux.vnet.ibm.com, pbonzini@...hat.com,
        alex.williamson@...hat.com, pmorel@...ux.vnet.ibm.com,
        alifm@...ux.vnet.ibm.com, mjrosato@...ux.vnet.ibm.com,
        jjherne@...ux.vnet.ibm.com, thuth@...hat.com,
        pasic@...ux.vnet.ibm.com, berrange@...hat.com,
        fiuczy@...ux.vnet.ibm.com, buendgen@...ibm.com
Subject: Re: [PATCH v4 01/15] s390: zcrypt: externalize AP instructions
 available function

On 15.04.2018 23:22, Tony Krowiak wrote:
> If the AP instructions are not available on the linux host, then
> AP devices can not be interpreted by the SIE. The AP bus has a

This statement is wrong. The instructions can be interpreted by SIE e.g.
if there are no devices assigned to a guest. This is e.g. the case for
!CONFIG_ZCRYPT.

Also, doesn't this directly imply that the other execution control
should also not be used ("intercept AP instuctions"). This would be bad.
Just because !CONFIG_ZCRYPT does not imply that you can't emulate AP
devices for a guest.

Why isn't it sufficient to glue CONFIG_ZCRYPT to vfio-ap? This would
make more sense in my opinion. You have no "host devices" that you can
"pass through". But you can still emulate devices or emulate an empty bus.

> function it uses to determine if the AP instructions are
> available. This patch provides a new function that wraps the
> AP bus's function to externalize it for use by KVM.
> 
> Signed-off-by: Tony Krowiak <akrowiak@...ux.vnet.ibm.com>
> Reviewed-by: Pierre Morel <pmorel@...ux.vnet.ibm.com>
> Reviewed-by: Harald Freudenberger <freude@...ux.vnet.ibm.com>
> ---
>  arch/s390/include/asm/ap.h     |    7 +++++++
>  arch/s390/include/asm/kvm-ap.h |   23 +++++++++++++++++++++++
>  arch/s390/kvm/Makefile         |    2 +-
>  arch/s390/kvm/kvm-ap.c         |   21 +++++++++++++++++++++
>  drivers/s390/crypto/ap_bus.c   |    6 ++++++
>  5 files changed, 58 insertions(+), 1 deletions(-)
>  create mode 100644 arch/s390/include/asm/kvm-ap.h
>  create mode 100644 arch/s390/kvm/kvm-ap.c
> 
> diff --git a/arch/s390/include/asm/ap.h b/arch/s390/include/asm/ap.h
> index c1bedb4..7773bfd 100644
> --- a/arch/s390/include/asm/ap.h
> +++ b/arch/s390/include/asm/ap.h
> @@ -120,4 +120,11 @@ struct ap_queue_status ap_queue_irq_ctrl(ap_qid_t qid,
>  					 struct ap_qirq_ctrl qirqctrl,
>  					 void *ind);
>  
> +/**
> + * ap_instructions_installed() - Tests whether AP instructions are installed
> + *
> + * Returns 1 if the AP instructions are installed, otherwise; returns 0
> + */
> +int ap_instructions_installed(void);
> +
>  #endif /* _ASM_S390_AP_H_ */
> diff --git a/arch/s390/include/asm/kvm-ap.h b/arch/s390/include/asm/kvm-ap.h
> new file mode 100644
> index 0000000..84412a9
> --- /dev/null
> +++ b/arch/s390/include/asm/kvm-ap.h
> @@ -0,0 +1,23 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Adjunct Processor (AP) configuration management for KVM guests
> + *
> + * Copyright IBM Corp. 2018
> + *
> + * Author(s): Tony Krowiak <akrowia@...ux.vnet.ibm.com>
> + */
> +
> +#ifndef _ASM_KVM_AP
> +#define _ASM_KVM_AP
> +
> +/**
> + * kvm_ap_instructions_installed()
> + *
> + * Tests whether AP instructions are installed on the linux host
> + *
> + * Returns 1 if the AP instructions are installed on the host, otherwise;
> + * returns 0
> + */
> +int kvm_ap_instructions_installed(void);
> +
> +#endif /* _ASM_KVM_AP */
> diff --git a/arch/s390/kvm/Makefile b/arch/s390/kvm/Makefile
> index 05ee90a..1876bfe 100644
> --- a/arch/s390/kvm/Makefile
> +++ b/arch/s390/kvm/Makefile
> @@ -9,6 +9,6 @@ common-objs = $(KVM)/kvm_main.o $(KVM)/eventfd.o  $(KVM)/async_pf.o $(KVM)/irqch
>  ccflags-y := -Ivirt/kvm -Iarch/s390/kvm
>  
>  kvm-objs := $(common-objs) kvm-s390.o intercept.o interrupt.o priv.o sigp.o
> -kvm-objs += diag.o gaccess.o guestdbg.o vsie.o
> +kvm-objs += diag.o gaccess.o guestdbg.o vsie.o kvm-ap.o
>  
>  obj-$(CONFIG_KVM) += kvm.o
> diff --git a/arch/s390/kvm/kvm-ap.c b/arch/s390/kvm/kvm-ap.c
> new file mode 100644
> index 0000000..1267588
> --- /dev/null
> +++ b/arch/s390/kvm/kvm-ap.c
> @@ -0,0 +1,21 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Adjunct Processor (AP) configuration management for KVM guests
> + *
> + * Copyright IBM Corp. 2018
> + *
> + * Author(s): Tony Krowiak <akrowia@...ux.vnet.ibm.com>
> + */
> +#include <linux/kernel.h>
> +#include <asm/kvm-ap.h>
> +#include <asm/ap.h>
> +
> +int kvm_ap_instructions_installed(void)
> +{
> +#ifdef CONFIG_ZCRYPT
> +	return ap_instructions_installed();
> +#else
> +	return 0;
> +#endif
> +}
> +EXPORT_SYMBOL(kvm_ap_instructions_installed);
> diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c
> index 35a0c2b..9d108b6 100644
> --- a/drivers/s390/crypto/ap_bus.c
> +++ b/drivers/s390/crypto/ap_bus.c
> @@ -210,6 +210,12 @@ int ap_query_configuration(struct ap_config_info *info)
>  }
>  EXPORT_SYMBOL(ap_query_configuration);
>  
> +int ap_instructions_installed(void)
> +{
> +	return (ap_instructions_available() == 0);
> +}
> +EXPORT_SYMBOL(ap_instructions_installed);
> +
>  /**
>   * ap_init_configuration(): Allocate and query configuration array.
>   */
> 


-- 

Thanks,

David / dhildenb