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

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Message-ID: <6eb0b596-c8b7-3529-55af-f3101821c74b@linux.ibm.com>
Date:   Tue, 18 Jan 2022 12:05:46 +0100
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     Matthew Rosato <mjrosato@...ux.ibm.com>, linux-s390@...r.kernel.org
Cc:     alex.williamson@...hat.com, cohuck@...hat.com,
        schnelle@...ux.ibm.com, farman@...ux.ibm.com,
        borntraeger@...ux.ibm.com, hca@...ux.ibm.com, gor@...ux.ibm.com,
        gerald.schaefer@...ux.ibm.com, agordeev@...ux.ibm.com,
        frankja@...ux.ibm.com, david@...hat.com, imbrenda@...ux.ibm.com,
        vneethv@...ux.ibm.com, oberpar@...ux.ibm.com, freude@...ux.ibm.com,
        thuth@...hat.com, pasic@...ux.ibm.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 22/30] KVM: s390: intercept the rpcit instruction



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@...ux.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