Re: [PATCH 24/32] KVM: s390: intercept the rpcit instruction

Pierre Morel
2021-12-14T17:03:06Z

On 12/7/21 21:57, Matthew Rosato wrote:
> For faster handling of PCI translation refreshes, intercept in KVM
> and call the associated handler.
>
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> ---
> arch/s390/kvm/pci.h | 4 ++++
> arch/s390/kvm/priv.c | 41 +++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 45 insertions(+)
>
> diff --git a/arch/s390/kvm/pci.h b/arch/s390/kvm/pci.h
> index d252a631b693..3f96eff432aa 100644
> --- a/arch/s390/kvm/pci.h
> +++ b/arch/s390/kvm/pci.h
> @@ -18,6 +18,10 @@
>
> #define KVM_S390_PCI_DTSM_MASK 0x40
>
> +#define KVM_S390_RPCIT_STAT_MASK 0xffffffff00ffffffUL
> +#define KVM_S390_RPCIT_INS_RES (0x10 << 24)
> +#define KVM_S390_RPCIT_ERR (0x28 << 24)

I

> +
> struct zpci_gaite {
> unsigned int gisa;
> u8 gisc;
> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
> index 417154b314a6..768ae92ecc59 100644
> --- a/arch/s390/kvm/priv.c
> +++ b/arch/s390/kvm/priv.c
> @@ -29,6 +29,7 @@
> #include <asm/ap.h>
> #include "gaccess.h"
> #include "kvm-s390.h"
> +#include "pci.h"
> #include "trace.h"
>
> static int handle_ri(struct kvm_vcpu *vcpu)
> @@ -335,6 +336,44 @@ static int handle_rrbe(struct kvm_vcpu *vcpu)
> return 0;
> }
>
> +static int handle_rpcit(struct kvm_vcpu *vcpu)
> +{
> + int reg1, reg2;
> + int rc;
> +
> + if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
> + return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
> +
> + kvm_s390_get_regs_rre(vcpu, &reg1, &reg2);
> +

I would prefer to take care of the interception immediately here

fh = vcpu->run->s.regs.gprs[reg1] >> 32;
if ((fh & aift.mdd) != 0)
return -EOPNOTSUP

instead of doing it inside kvm_s390_pci_refresh_trans.
It would simplify in my opinion.

> + rc = kvm_s390_pci_refresh_trans(vcpu, vcpu->run->s.regs.gprs[reg1],
> + vcpu->run->s.regs.gprs[reg2],
> + vcpu->run->s.regs.gprs[reg2+1]);
> +

> + switch (rc) {
> + case 0:
> + kvm_s390_set_psw_cc(vcpu, 0);
> + break;
> + case -EOPNOTSUPP:
> + return -EOPNOTSUPP;
> + case -EINVAL:
> + kvm_s390_set_psw_cc(vcpu, 3);
> + break;
> + case -ENOMEM:
> + vcpu->run->s.regs.gprs[reg1] &= KVM_S390_RPCIT_STAT_MASK;
> + vcpu->run->s.regs.gprs[reg1] |= KVM_S390_RPCIT_INS_RES;
> + kvm_s390_set_psw_cc(vcpu, 1);
> + break;
> + default:
> + vcpu->run->s.regs.gprs[reg1] &= KVM_S390_RPCIT_STAT_MASK;
> + vcpu->run->s.regs.gprs[reg1] |= KVM_S390_RPCIT_ERR;

I think you should use the status reported by the hardware, reporting
"Error recovery in progress" what ever the hardware error was does not
seem right.

> + kvm_s390_set_psw_cc(vcpu, 1);
> + break;
> + }

NIT: This switch above could be much more simple if you set CC after the
switch.

> +
> + return 0;
> +}
> +
> #define SSKE_NQ 0x8
> #define SSKE_MR 0x4
> #define SSKE_MC 0x2
> @@ -1275,6 +1314,8 @@ int kvm_s390_handle_b9(struct kvm_vcpu *vcpu)
> return handle_essa(vcpu);
> case 0xaf:
> return handle_pfmf(vcpu);
> + case 0xd3:
> + return handle_rpcit(vcpu);
> default:
> return -EOPNOTSUPP;
> }
>

--
Pierre Morel
IBM Lab Boeblingen