Re: [PATCH v8 1/4] s390: ap: kvm: add PQAP interception for AQIC

[Tony Krowiak]

On 5/2/19 1:34 PM, Pierre Morel wrote:
> We prepare the interception of the PQAP/AQIC instruction for
> the case the AQIC facility is enabled in the guest.
>
> First of all we do not want to change existing behavior when
> intercepting AP instructions without the SIE allowing the guest
> to use AP instructions.
>
> In this patch we only handle the AQIC interception allowed by
> facility 65 which will be enabled when the complete interception
> infrastructure will be present.
>
> We add a callback inside the KVM arch structure for s390 for
> a VFIO driver to handle a specific response to the PQAP
> instruction with the AQIC command and only this command.
>
> But we want to be able to return a correct answer to the guest
> even there is no VFIO AP driver in the kernel.
> Therefor, we inject the correct exceptions from inside KVM for the
> case the callback is not initialized, which happens when the vfio_ap
> driver is not loaded.
>
> We do consider the responsability of the driver to always initialize
> the PQAP callback if it defines queues by initializing the CRYCB for
> a guest.
> If the callback has been setup we call it.
> If not we setup an answer considering that no queue is available
> for the guest when no callback has been setup.
>
> Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
> ---
>   arch/s390/include/asm/kvm_host.h      |  7 +++
>   arch/s390/kvm/priv.c                  | 86 +++++++++++++++++++++++++++++++++++
>   drivers/s390/crypto/vfio_ap_private.h |  2 +
>   3 files changed, 95 insertions(+)
>
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index 9fff9ab..af10a11 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -18,6 +18,7 @@
>   #include <linux/kvm_host.h>
>   #include <linux/kvm.h>
>   #include <linux/seqlock.h>
> +#include <linux/module.h>
>   #include <asm/debug.h>
>   #include <asm/cpu.h>
>   #include <asm/fpu/api.h>
> @@ -722,8 +723,14 @@ struct kvm_s390_cpu_model {
>   	unsigned short ibc;
>   };
>   
> +struct kvm_s390_module_hook {
> +	int (*hook)(struct kvm_vcpu *vcpu);
> +	struct module *owner;
> +};
> +
>   struct kvm_s390_crypto {
>   	struct kvm_s390_crypto_cb *crycb;
> +	struct kvm_s390_module_hook *pqap_hook;
>   	__u32 crycbd;
>   	__u8 aes_kw;
>   	__u8 dea_kw;
> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
> index 8679bd7..a9be84f 100644
> --- a/arch/s390/kvm/priv.c
> +++ b/arch/s390/kvm/priv.c
> @@ -27,6 +27,7 @@
>   #include <asm/io.h>
>   #include <asm/ptrace.h>
>   #include <asm/sclp.h>
> +#include <asm/ap.h>
>   #include "gaccess.h"
>   #include "kvm-s390.h"
>   #include "trace.h"
> @@ -592,6 +593,89 @@ static int handle_io_inst(struct kvm_vcpu *vcpu)
>   	}
>   }
>   
> +/*
> + * handle_pqap: Handling pqap interception
> + * @vcpu: the vcpu having issue the pqap instruction
> + *
> + * We now support PQAP/AQIC instructions and we need to correctly
> + * answer the guest even if no dedicated driver's hook is available.
> + *
> + * The intercepting code calls a dedicated callback for this instruction
> + * if a driver did register one in the CRYPTO satellite of the
> + * SIE block.
> + *
> + * If no callback is available, the queues are not available, return this
> + * response code to the caller and set CC to 3.
> + * Else return the response code returned by the callback.
> + */
> +static int handle_pqap(struct kvm_vcpu *vcpu)
> +{
> +	struct ap_queue_status status = {};
> +	unsigned long reg0;
> +	int ret;
> +	uint8_t fc;
> +
> +	/* Verify that the AP instruction are available */
> +	if (!ap_instructions_available())
> +		return -EOPNOTSUPP;
> +	/* Verify that the guest is allowed to use AP instructions */
> +	if (!(vcpu->arch.sie_block->eca & ECA_APIE))
> +		return -EOPNOTSUPP;
> +	/*
> +	 * The only possibly intercepted functions when AP instructions are
> +	 * available for the guest are AQIC and TAPQ with the t bit set
> +	 * since we do not set IC.3 (FIII) we currently will only intercept
> +	 * the AQIC function code.
> +	 */
> +	reg0 = vcpu->run->s.regs.gprs[0];
> +	fc = reg0 >> 24;

Should you also mask off bits 0-32 in case they might not be zeroes?

Other than this, r-b

> +	if (WARN_ON_ONCE(fc != 0x03))
> +		return -EOPNOTSUPP;
> +
> +	/* PQAP instruction is allowed for guest kernel only */
> +	if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
> +		return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
> +
> +	/* Common PQAP instruction specification exceptions */
> +	/* bits 41-47 must all be zeros */
> +	if (reg0 & 0x007f0000UL)
> +		return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
> +	/* APFT not install and T bit set */
> +	if (!test_kvm_facility(vcpu->kvm, 15) && (reg0 & 0x00800000UL))
> +		return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
> +	/* APXA not installed and APID greater 64 or APQI greater 16 */
> +	if (!(vcpu->kvm->arch.crypto.crycbd & 0x02) && (reg0 & 0x0000c0f0UL))
> +		return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
> +
> +	/* AQIC function code specific exception */
> +	/* facility 65 not present for AQIC function code */
> +	if (!test_kvm_facility(vcpu->kvm, 65))
> +		return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
> +
> +	/*
> +	 * Verify that the hook callback is registered, lock the owner
> +	 * and call the hook.
> +	 */
> +	if (vcpu->kvm->arch.crypto.pqap_hook) {
> +		if (!try_module_get(vcpu->kvm->arch.crypto.pqap_hook->owner))
> +			return -EOPNOTSUPP;
> +		ret = vcpu->kvm->arch.crypto.pqap_hook->hook(vcpu);
> +		module_put(vcpu->kvm->arch.crypto.pqap_hook->owner);
> +		if (!ret && vcpu->run->s.regs.gprs[1] & 0x00ff0000)
> +			kvm_s390_set_psw_cc(vcpu, 3);
> +		return ret;
> +	}
> +	/*
> +	 * A vfio_driver must register a hook.
> +	 * No hook means no driver to enable the SIE CRYCB and no queues.
> +	 * We send this response to the guest.
> +	 */
> +	status.response_code = 0x01;
> +	memcpy(&vcpu->run->s.regs.gprs[1], &status, sizeof(status));
> +	kvm_s390_set_psw_cc(vcpu, 3);
> +	return 0;
> +}
> +
>   static int handle_stfl(struct kvm_vcpu *vcpu)
>   {
>   	int rc;
> @@ -878,6 +962,8 @@ int kvm_s390_handle_b2(struct kvm_vcpu *vcpu)
>   		return handle_sthyi(vcpu);
>   	case 0x7d:
>   		return handle_stsi(vcpu);
> +	case 0xaf:
> +		return handle_pqap(vcpu);
>   	case 0xb1:
>   		return handle_stfl(vcpu);
>   	case 0xb2:
> diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
> index 76b7f98..a910be1 100644
> --- a/drivers/s390/crypto/vfio_ap_private.h
> +++ b/drivers/s390/crypto/vfio_ap_private.h
> @@ -16,6 +16,7 @@
>   #include <linux/mdev.h>
>   #include <linux/delay.h>
>   #include <linux/mutex.h>
> +#include <linux/kvm_host.h>
>   
>   #include "ap_bus.h"
>   
> @@ -81,6 +82,7 @@ struct ap_matrix_mdev {
>   	struct ap_matrix matrix;
>   	struct notifier_block group_notifier;
>   	struct kvm *kvm;
> +	struct kvm_s390_module_hook pqap_hook;
>   };
>   
>   extern int vfio_ap_mdev_register(void);