From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Krowiak Subject: Re: [PATCH v6 1/7] s390: ap: kvm: add PQAP interception for AQIC Date: Wed, 27 Mar 2019 12:06:53 -0400 Message-ID: <847ca906-f6d6-37e5-9cd1-111834b70122@linux.ibm.com> References: <1553265828-27823-1-git-send-email-pmorel@linux.ibm.com> <1553265828-27823-2-git-send-email-pmorel@linux.ibm.com> <66abb1f6-425a-df94-cc7c-f1fdec0ece9c@linux.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: alex.williamson@redhat.com, cohuck@redhat.com, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, frankja@linux.ibm.com, pasic@linux.ibm.com, david@redhat.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, freude@linux.ibm.com, mimu@linux.ibm.com To: Pierre Morel , borntraeger@de.ibm.com Return-path: In-Reply-To: <66abb1f6-425a-df94-cc7c-f1fdec0ece9c@linux.ibm.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 3/26/19 2:57 PM, Tony Krowiak wrote: > On 3/22/19 10:43 AM, 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 >> --- >>   arch/s390/include/asm/kvm_host.h      |  8 ++++ >>   arch/s390/kvm/priv.c                  | 90 >> +++++++++++++++++++++++++++++++++++ >>   drivers/s390/crypto/vfio_ap_private.h |  2 + >>   3 files changed, 100 insertions(+) >> >> diff --git a/arch/s390/include/asm/kvm_host.h >> b/arch/s390/include/asm/kvm_host.h >> index a496276..624460b 100644 >> --- a/arch/s390/include/asm/kvm_host.h >> +++ b/arch/s390/include/asm/kvm_host.h >> @@ -18,6 +18,7 @@ >>   #include >>   #include >>   #include >> +#include >>   #include >>   #include >>   #include >> @@ -721,8 +722,15 @@ struct kvm_s390_cpu_model { >>       unsigned short ibc; >>   }; >> +struct kvm_s390_module_hook { >> +    int (*hook)(struct kvm_vcpu *vcpu); >> +    void *data; >> +    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..793e48a 100644 >> --- a/arch/s390/kvm/priv.c >> +++ b/arch/s390/kvm/priv.c >> @@ -27,6 +27,7 @@ >>   #include >>   #include >>   #include >> +#include >>   #include "gaccess.h" >>   #include "kvm-s390.h" >>   #include "trace.h" >> @@ -592,6 +593,93 @@ 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. >> + * >> + * For PQAP AQIC and TAPQ instructions, verify privilege and >> specifications. > > The two paragraphs above should be described via the comments embedded > in the code and is not necessary here. > >> + * >> + * If no callback available, the queues are not available, return >> this to >> + * the caller. > > This implies it is specified via the return code when it is in fact > the response code in the status word. > >> + * Else return the value returned by the callback. >> + */ > > Given this handler may be called for any PQAP instruction sub-function, > I think the function doc should be more generic, providing: > > * A general description of what the function does > * A description of each input parameter > * A description of the value returned. If the return value is a return >   code, the possible rc values can be enumerated with a description for >   of the reason each particular value may be returned. > >> +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 instructions 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 not intercept >> +     * TAPQ. >> +     * The following code will only treat AQIC function code. >> +     */ > > Simplify to: > > /* The only supported PQAP function is AQIC (0x03) */ > >> +    reg0 = vcpu->run->s.regs.gprs[0]; >> +    fc = reg0 >> 24; >> +    if (fc != 0x03) { >> +        pr_warn("%s: Unexpected interception code 0x%02x\n", >> +            __func__, fc); >> +        return -EOPNOTSUPP; >> +    } >> +    /* All PQAP instructions are allowed for guest kernel only */ > > There is only one PQAP instruction with multiple sub-functions. > /* PQAP instruction is allowed for guest kernel only */ >                         or > /* PQAP instruction is privileged */ > >> +    if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE) >> +        return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP); >> +    /* >> +     * Common tests for PQAP instructions to generate a specification >> +     * exception >> +     */ > > This comment is unnecessary as the individual comments below adequately > do the job. > >> +    /* Zero bits overwrite produce a specification exception */ > > This comment has no meaning unless you intimately know the architecture. > The following would make more sense: > >     /* Bits 41-47 must all be zeros */ > > It's probably not a big deal, but since we don't support PQAP(TAPQ), > would it make more sense to make sure bits 40-47 are zeros (i.e., > the 't' bit is not set)? > >> +    if (reg0 & 0x007f0000UL) >> +        goto specification_except; >> +    /* If APXA is not installed APQN is limited */ > > Wouldn't it be better to state how the APQN is limited? > For example: > >     /* >      * If APXA is not installed, then the maximum APID is >      * 63 (bits 48-49 of reg0 must be zero) and the maximum >      * APQI is 15 (bits 56-59 must be zero) >      */ > >> +    if (!(vcpu->kvm->arch.crypto.crycbd & 0x02)) >> +        if (reg0 & 0x000030f0UL) > > If APXA is not installed, then bits 48-49 and 56-59 must all be > zeros. Shouldn't this mask be 0x0000c0f0UL? > >> +            goto specification_except; >> +    /* AQIC needs facility 65 */ >> +    if (!test_kvm_facility(vcpu->kvm, 65)) >> +        goto specification_except; >> + >> +    /* >> +     * 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); >> +        return ret; >> +    } >> +    /* >> +     * It is the duty of the vfio_driver to register a hook >> +     * If it does not and we get an exception on AQIC we must >> +     * guess that there is no vfio_ap_driver at all and no one >> +     * to handle the guests's CRYCB and the CRYCB is empty. >> +     */ > > The comment above does not make sense to me. If there is no pqap > hook registered, then we need to handle that case for sure. But why > mention getting an exception? Why even mention whose responsibility > it is to set the hook when all we need to know is whether a hook is > set or not? > > I am wondering whether merely setting a response code indicating the > APQN is invalid is the correct thing to do here. First of all, if the > guest's CRYCB is empty, then the AP bus running in the guest would not > create any AP devices or any AP queues bound to any zcrypt driver. In > that case, I don't think the PQAP(AQIC) would ever be issued. If a > PQAP is intercepted, wouldn't we want to return -EOPNOTSUPP? I dug back through the previous comments and see this has been discussed before, so you can ignore this comment. > > > >> +    status.response_code = 0x01; >> +    memcpy(&vcpu->run->s.regs.gprs[1], &status, sizeof(status)); >> +    return 0; >> + >> +specification_except: >> +    return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION); >> +} >> + >>   static int handle_stfl(struct kvm_vcpu *vcpu) >>   { >>       int rc; >> @@ -878,6 +966,8 @@ 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.hhttps://www.linuxmint.com/start/sylvia/ >> >> @@ -16,6 +16,7 @@ >>   #include >>   #include >>   #include >> +#include >>   #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); >> >