Re: [PATCH v2 22/30] KVM: s390: intercept the rpcit instruction

Pierre Morel
2022-01-18T11:04:14Z

On 1/14/22 21:31, 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/priv.c | 46 ++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 46 insertions(+)
>
> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
> index 417154b314a6..5b65c1830de2 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 +336,49 @@ static int handle_rrbe(struct kvm_vcpu *vcpu)
> return 0;
> }
>
> +static int handle_rpcit(struct kvm_vcpu *vcpu)
> +{
> + int reg1, reg2;
> + u8 status;
> + int rc;
> +
> + if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
> + return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
> +
> + /* If the host doesn't support PCI, it must be an emulated device */
> + if (!IS_ENABLED(CONFIG_PCI))
> + return -EOPNOTSUPP;

AFAIU this makes also sure that the following code is not compiled in
case PCI is not supported.

I am not very used to compilation options, is it true with all our
compilers and options?
Or do we have to specify a compiler version?

Another concern is, shouldn't we use IS_ENABLED(CONFIG_VFIO_PCI) ?

> +
> + kvm_s390_get_regs_rre(vcpu, &reg1, &reg2);
> +
> + /* If the device has a SHM bit on, let userspace take care of this */
> + if (((vcpu->run->s.regs.gprs[reg1] >> 32) & aift->mdd) != 0)
> + return -EOPNOTSUPP;
> +
> + 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],
> + &status);
> +
> + switch (rc) {
> + case 0:
> + kvm_s390_set_psw_cc(vcpu, 0);
> + break;
> + case -EOPNOTSUPP:
> + return -EOPNOTSUPP;
> + default:
> + vcpu->run->s.regs.gprs[reg1] &= 0xffffffff00ffffffUL;
> + vcpu->run->s.regs.gprs[reg1] |= (u64) status << 24;
> + if (status != 0)
> + kvm_s390_set_psw_cc(vcpu, 1);
> + else
> + kvm_s390_set_psw_cc(vcpu, 3);
> + break;
> + }
> +
> + return 0;
> +}
> +
> #define SSKE_NQ 0x8
> #define SSKE_MR 0x4
> #define SSKE_MC 0x2
> @@ -1275,6 +1319,8 @@ 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