Re: [PATCH v9 07/22] KVM: s390: refactor crypto initialization

[David Hildenbrand <david@redhat.com>]

On 13.08.2018 23:48, Tony Krowiak wrote:
> From: Tony Krowiak <akrowiak@linux.ibm.com>
> 
> This patch refactors the code that initializes and sets up the
> crypto configuration for a guest. The following changes are
> implemented via this patch:
> 
> 1. Prior to the introduction of AP device virtualization, it
>    was not necessary to provide guest access to the CRYCB
>    unless the MSA extension 3 (MSAX3) facility was installed
>    on the host system. With the introduction of AP device
>    virtualization, the CRYCB must be made accessible to the
>    guest if the AP instructions are installed on the host
>    and are to be provided to the guest.
> 
> 2. Introduces a flag indicating AP instructions executed on
>    the guest shall be interpreted by the firmware. It is
>    initialized to indicate AP instructions are to be
>    to be interpreted and is used to set the SIE bit for
>    each vcpu during vcpu setup.
> 
> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Acked-by: Janosch Frank <frankja@linux.ibm.com>
> Tested-by: Michael Mueller <mimu@linux.ibm.com>
> Tested-by: Farhan Ali <alifm@linux.ibm.com>
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
>  arch/s390/include/asm/kvm_host.h |    2 +
>  arch/s390/include/uapi/asm/kvm.h |    1 +
>  arch/s390/kvm/kvm-s390.c         |   81 +++++++++++++++++++-------------------
>  3 files changed, 44 insertions(+), 40 deletions(-)
> 
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index af39561..4a739d4 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -187,6 +187,7 @@ struct kvm_s390_sie_block {
>  #define ECA_AIV		0x00200000
>  #define ECA_VX		0x00020000
>  #define ECA_PROTEXCI	0x00002000
> +#define ECA_APIE	0x00000008
>  #define ECA_SII		0x00000001
>  	__u32	eca;			/* 0x004c */
>  #define ICPT_INST	0x04
> @@ -256,6 +257,7 @@ struct kvm_s390_sie_block {
>  	__u8	reservede4[4];		/* 0x00e4 */
>  	__u64	tecmc;			/* 0x00e8 */
>  	__u8	reservedf0[12];		/* 0x00f0 */
> +#define CRYCB_FORMAT_MASK 0x00000003
>  #define CRYCB_FORMAT1 0x00000001
>  #define CRYCB_FORMAT2 0x00000003
>  	__u32	crycbd;			/* 0x00fc */
> diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
> index 4cdaa55..a580dec 100644
> --- a/arch/s390/include/uapi/asm/kvm.h
> +++ b/arch/s390/include/uapi/asm/kvm.h
> @@ -130,6 +130,7 @@ struct kvm_s390_vm_cpu_machine {
>  #define KVM_S390_VM_CPU_FEAT_PFMFI	11
>  #define KVM_S390_VM_CPU_FEAT_SIGPIF	12
>  #define KVM_S390_VM_CPU_FEAT_KSS	13
> +#define KVM_S390_VM_CPU_FEAT_AP		14
>  struct kvm_s390_vm_cpu_feat {
>  	__u64 feat[16];
>  };
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 19f4f44..f7de123 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -40,6 +40,7 @@
>  #include <asm/sclp.h>
>  #include <asm/cpacf.h>
>  #include <asm/timex.h>
> +#include <asm/ap.h>
>  #include "kvm-s390.h"
>  #include "gaccess.h"
>  
> @@ -1881,49 +1882,37 @@ long kvm_arch_vm_ioctl(struct file *filp,
>  	return r;
>  }
>  
> -static int kvm_s390_query_ap_config(u8 *config)
> -{
> -	u32 fcn_code = 0x04000000UL;
> -	u32 cc = 0;
> -
> -	memset(config, 0, 128);
> -	asm volatile(
> -		"lgr 0,%1\n"
> -		"lgr 2,%2\n"
> -		".long 0xb2af0000\n"		/* PQAP(QCI) */
> -		"0: ipm %0\n"
> -		"srl %0,28\n"
> -		"1:\n"
> -		EX_TABLE(0b, 1b)
> -		: "+r" (cc)
> -		: "r" (fcn_code), "r" (config)
> -		: "cc", "0", "2", "memory"
> -	);
> -
> -	return cc;
> -}
> -
>  static int kvm_s390_apxa_installed(void)
>  {
> -	u8 config[128];
> -	int cc;
> +	struct ap_config_info info;
>  
> -	if (test_facility(12)) {
> -		cc = kvm_s390_query_ap_config(config);
> -
> -		if (cc)
> -			pr_err("PQAP(QCI) failed with cc=%d", cc);
> -		else
> -			return config[0] & 0x40;
> +	if (ap_instructions_available()) {
> +		if (ap_qci(&info) == 0)
> +			return info.apxa;
>  	}
>  
>  	return 0;
>  }
>  
> +/*
> + * The format of the crypto control block (CRYCB) is specified in the 3 low
> + * order bits of the CRYCB designation (CRYCBD) field as follows:
> + * Format 0: Neither the message security assist extension 3 (MSAX3) nor the
> + *	     AP extended addressing (APXA) facility are installed.
> + * Format 1: The APXA facility is not installed but the MSAX3 facility is.
> + * Format 2: Both the APXA and MSAX3 facilities are installed
> + */
>  static void kvm_s390_set_crycb_format(struct kvm *kvm)
>  {
>  	kvm->arch.crypto.crycbd = (__u32)(unsigned long) kvm->arch.crypto.crycb;
>  
> +	/* Clear the CRYCB format bits - i.e., set format 0 by default */
> +	kvm->arch.crypto.crycbd &= ~(CRYCB_FORMAT_MASK);
> +
> +	/* Check whether MSAX3 is installed */
> +	if (!test_kvm_facility(kvm, 76))
> +		return;
> +
>  	if (kvm_s390_apxa_installed())
>  		kvm->arch.crypto.crycbd |= CRYCB_FORMAT2;
>  	else
> @@ -1941,12 +1930,12 @@ static u64 kvm_s390_get_initial_cpuid(void)
>  
>  static void kvm_s390_crypto_init(struct kvm *kvm)
>  {
> -	if (!test_kvm_facility(kvm, 76))
> -		return;
> -
>  	kvm->arch.crypto.crycb = &kvm->arch.sie_page2->crycb;
>  	kvm_s390_set_crycb_format(kvm);
>  
> +	if (!test_kvm_facility(kvm, 76))
> +		return;
> +
>  	/* Enable AES/DEA protected key functions by default */
>  	kvm->arch.crypto.aes_kw = 1;
>  	kvm->arch.crypto.dea_kw = 1;
> @@ -2474,17 +2463,29 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
>  
>  static void kvm_s390_vcpu_crypto_setup(struct kvm_vcpu *vcpu)
>  {
> -	if (!test_kvm_facility(vcpu->kvm, 76))
> +	/*
> +	 * If neither the AP instructions nor the MSAX3 facility are installed
> +	 * on the host, then there is no need for a CRYCB in SIE because they
> +	 * will not be installed on the guest either.
> +	 */
> +	if (!test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_AP) &&
> +	    !test_facility(76))

I think this can just stay "test_kvm_facility(vcpu->kvm, 76)", and the
comment should be changed to

"If neither the AP instructions nor the MSAX3 facility are configured
for the guest, there is nothing to set up."

Or am I missing something important here?

After the CPU has been created, both feature can no longer change. The
only thing that might change is kvm->arch.crypto.aes_kw/dea_kw but only
with test_kvm_facility(vcpu->kvm, 76).

>  		return;
>  
> +	vcpu->arch.sie_block->crycbd = vcpu->kvm->arch.crypto.crycbd;
>  	vcpu->arch.sie_block->ecb3 &= ~(ECB3_AES | ECB3_DEA);
>  
> -	if (vcpu->kvm->arch.crypto.aes_kw)
> -		vcpu->arch.sie_block->ecb3 |= ECB3_AES;
> -	if (vcpu->kvm->arch.crypto.dea_kw)
> -		vcpu->arch.sie_block->ecb3 |= ECB3_DEA;
> +	vcpu->arch.sie_block->eca &= ~ECA_APIE;

As this feature can never flip, clearing the flag is not necessary.

> +	if (test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_AP))
> +		vcpu->arch.sie_block->eca |= ECA_APIE;
>  
> -	vcpu->arch.sie_block->crycbd = vcpu->kvm->arch.crypto.crycbd;
> +	/* If MSAX3 is installed on the guest, set up protected key support */
> +	if (test_kvm_facility(vcpu->kvm, 76)) {
> +		if (vcpu->kvm->arch.crypto.aes_kw)
> +			vcpu->arch.sie_block->ecb3 |= ECB3_AES;
> +		if (vcpu->kvm->arch.crypto.dea_kw)
> +			vcpu->arch.sie_block->ecb3 |= ECB3_DEA;
> +	}

As the feature can never change, and aes_kw/dea_kw are only set to 1 in
case we have test_kvm_facility(vcpu->kvm, 76), this change is not needed.

I think this function can be pretty much left alone. Just add the
KVM_S390_VM_CPU_FEAT_AP handling.

>  }
>  
>  void kvm_s390_vcpu_unsetup_cmma(struct kvm_vcpu *vcpu)
> 


-- 

Thanks,

David / dhildenb