Re: [PATCH v3 2/9] s390: ap: kvm: setting a hook for PQAP instructions

Cornelia Huck
2019-02-14T15:54:07Z

On Thu, 14 Feb 2019 14:51:02 +0100
Pierre Morel <pmorel@linux.ibm.com> wrote:

> This patch adds interception code for the PQAP instructions,
> and a callback inside the KVM arch structure for s390.
>
> If a VFIO-AP drivers needs to intercept PQAP/AQIC or PQAP/TAPQ

s/drivers/driver/

> instructions, the driver will initialize the callback inside
> the kvm_arch structure to be called when the interception of a
> PQAP instruction occurs.
>
> If the callback is not initialized, the code still returns
> -EOPNOTSUPP to let userland handle the instruction as it used to.
>
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> Reviewed-by: Tony Krowiak <akrowiak@linux.ibm.com>
> ---
> arch/s390/include/asm/kvm_host.h | 1 +
> arch/s390/kvm/priv.c | 50 ++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 51 insertions(+)
>
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index c5f5156..49cc8b0 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -719,6 +719,7 @@ struct kvm_s390_cpu_model {
>
> struct kvm_s390_crypto {
> struct kvm_s390_crypto_cb *crycb;
> + int (*pqap_hook)(struct kvm_vcpu *vcpu);
> __u32 crycbd;
> __u8 aes_kw;
> __u8 dea_kw;
> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
> index 8679bd7..72fdc21 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 +593,53 @@ static int handle_io_inst(struct kvm_vcpu *vcpu)
> }
> }
>
> +/*
> + * handle_pqap: Handling pqap interception
> + * @vcpu: the vcpu having issue the pqap instruction

s/issue/issued/

> + *
> + * This callback only handles PQAP/AQIC instruction and

Here you only talk about PQAP/AQIC, what about PQAP/TAPQ mentioned in
the patch description?

> + * calls a dedicated callback for this instruction if
> + * a driver did register one in the CRYPTO satellite of the
> + * SIE block.
> + *
> + * Do not change the behavior if, return -EOPNOTSUPP if:
> + * - the hook is not used do not change the behavior.

The hook is not used? Or not set? (I don't think you need to repeat "do
not change the behavior".)

> + * - AP instructions are not available or not available to the guest
> + * - the instruction is not PQAP with function code indicating
> + * AQIC do not change the previous behavior.
> + *
> + * For PQAP/AQIC instruction, verify privilege and specifications
> + *
> + * return the value returned by the callback.
> + */
> +static int handle_pqap(struct kvm_vcpu *vcpu)
> +{
> + uint8_t fc;
> +
> + /* Verify that the hook callback is registered */
> + if (!vcpu->kvm->arch.crypto.pqap_hook)
> + return -EOPNOTSUPP;
> + /* 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;
> + /* Verify that the function code is AQIC */
> + fc = vcpu->run->s.regs.gprs[0] >> 24;
> + if (fc != 0x03)
> + return -EOPNOTSUPP;
> +
> + /* PQAP instructions are 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);
> + /* AQIC instruction is allowed only if facility 65 is available */
> + if (!test_kvm_facility(vcpu->kvm, 65))
> + return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
> + /* All right, call the callback */
> + return vcpu->kvm->arch.crypto.pqap_hook(vcpu);

Can that callback also return -EOPNOTSUPP to order to drop to user
space?

> +}
> +
> static int handle_stfl(struct kvm_vcpu *vcpu)
> {
> int rc;
> @@ -878,6 +926,8 @@ 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: