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

[Pierre Morel]

On 08/05/2019 17:48, Tony Krowiak wrote:
> 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>
> > ---
> > Â arch/s390/include/asm/kvm_host.hÂÂÂÂÂ |Â 7 +++
> > Â arch/s390/kvm/priv.cÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ | 86 
> > +++++++++++++++++++++++++++++++++++
> > Â drivers/s390/crypto/vfio_ap_private.h |Â 2 +
> > Â 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 @@
> > Â #include <linux/kvm_host.h>
> > Â #include <linux/kvm.h>
> > Â #include <linux/seqlock.h>
> > +#include <linux/module.h>
> > Â #include <asm/debug.h>
> > Â #include <asm/cpu.h>
> > Â #include <asm/fpu/api.h>
> > @@ -722,8 +723,14 @@ struct kvm_s390_cpu_model {
> > ÂÂÂÂÂ unsigned short ibc;
> > Â };
> > +struct kvm_s390_module_hook {
> > +ÂÂÂ int (*hook)(struct kvm_vcpu *vcpu);
> > +ÂÂÂ struct module *owner;
> > +};
> > +
> > Â struct kvm_s390_crypto {
> > ÂÂÂÂÂ struct kvm_s390_crypto_cb *crycb;
> > +ÂÂÂ struct kvm_s390_module_hook *pqap_hook;
> > ÂÂÂÂÂ __u32 crycbd;
> > ÂÂÂÂÂ __u8 aes_kw;
> > ÂÂÂÂÂ __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 @@
> > Â #include <asm/io.h>
> > Â #include <asm/ptrace.h>
> > Â #include <asm/sclp.h>
> > +#include <asm/ap.h>
> > Â #include "gaccess.h"
> > Â #include "kvm-s390.h"
> > Â #include "trace.h"
> > @@ -592,6 +593,89 @@ static int handle_io_inst(struct kvm_vcpu *vcpu)
> > ÂÂÂÂÂ }
> > Â }
> > +/*
> > + * 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)
> > +{
> > +ÂÂÂ struct ap_queue_status status = {};
> > +ÂÂÂ unsigned long reg0;
> > +ÂÂÂ int ret;
> > +ÂÂÂ uint8_t fc;
> > +
> > +ÂÂÂ /* Verify that the AP instruction are available */
> > +ÂÂÂ if (!ap_instructions_available())
> > +ÂÂÂÂÂÂÂ return -EOPNOTSUPP;
> > +ÂÂÂ /* Verify that the guest is allowed to use AP instructions */
> > +ÂÂÂ if (!(vcpu->arch.sie_block->eca & ECA_APIE))
> > +ÂÂÂÂÂÂÂ return -EOPNOTSUPP;
> > +ÂÂÂ /*
> > +ÂÂÂÂ * The only possibly intercepted functions when AP instructions are
> > +ÂÂÂÂ * available for the guest are AQIC and TAPQ with the t bit set
> > +ÂÂÂÂ * since we do not set IC.3 (FIII) we currently will only intercept
> > +ÂÂÂÂ * the AQIC function code.
> > +ÂÂÂÂ */
> > +ÂÂÂ reg0 = vcpu->run->s.regs.gprs[0];
> > +ÂÂÂ fc = reg0 >> 24;
>
> Should you also mask off bits 0-32 in case they might not be zeroes?

Yes I will.

> Other than this, r-b

Thanks,

Pierre

--
Pierre Morel
Linux/KVM/QEMU in BÃblingen - Germany